MAX25220ATJ_技术文档

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MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

General Description

Benefits and Features

The MAX25220/MAX25221/MAX25221B are 4-channel

TFT-LCD power ICs that provide symmetrical positive

● High Integration

• Synchronous Boost Provides AVDD of 4.2V to

10.5V at up to 200mA

AVDD and negative NAVDD supplies as well as VG

ON

and VG

gate supplies. In addition, a VCOM buffer with

• NAVDD Inverter Output at up to -200mA

OFF

output voltage range above and below ground and a tem-

• 15mA VG

Output (7.6V to 20.2V) from 3x

ON

perature measurement block are integrated (MAX25221/

B).

Regulated Charge Pump

• VG

(-18.2V to -5.6V) from Regulated Charge

OFF

Pump at up to -15mA (charge-pump doubler)

• Controlled Sequencing during Power-On and

Power-Off of All Rails

• VCOM Output Range +1V to -2.49V in 6.83mV

Steps (MAX25221)

• NTC Input for Temperature Measurement/

Compensation (MAX25221)

The devices contain non-volatile memory so that the val-

ues of all outputs can be calibrated for the lifetime of the

device (maximum five times).

2

Programming is carried out using the built-in I C interface,

which can also be used to read back diagnostic informa-

tion. A stand-alone mode is also available.

The temperature sensor interface block measures the

temperature optionally allowing the VCOM output voltage

to be adjusted depending on the measured temperature.

● Low EMI

• 420kHz/2.1MHz Switching Frequency with Spread

Spectrum

The MAX25220/MAX25221/MAX25221B are available in

a TQFN package and operate in the -40 to 125°C temper-

ature range.

2

● I C Control/Diagnostic Interface with FLTB (Interrupt)

Output

• UV diagnostics on All Outputs

● Versatile

Applications

• Non-Volatile Output Voltage Settings on AVDD/

● Infotainment Displays

● Central Information Displays

● Instrument Clusters

NAVDD, VG , VG

, VCOM, and Sequencing

ON

OFF

• Supports Stand-Alone Operation Mode after

Programming

• Compact 5mm x 5mm TQFN32 Package

● AECQ100 Grade 1

Ordering Information appears at end of datasheet.

19-100803; Rev 4; 11/20

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Simplified Block Diagram

RREF TEMP

V18

IN

DAC

REG

VCOM

8b ADC FOR

TEMP

COMPENSATION

VCOMN

BST

NAVDD

NEG.

REGULATOR

VCB

PGVDD

FC2+

TFT BOOST

CONTROL

420kHz/2.1MHz

UVLO

HVINP

LXP

FC2-

PGND

POSITIVE

CHARGE PUMP

FC1+

0.9V

TEMP

WARNING,

SHUTDOWN

FC1-

HVINP

AVDD

VGON

REFERENCE

POSITIVE

SOFT-START

AND

VGOFF

DN

DISCHARGE

ENABLE, CONTROL

AND FAULT LOGIC

NEGATIVE

CHARGE PUMP

NEGATIVE

SOFT-START

AND

NAVDD

DISCHARGE

CPGND

EN

FLTB

DGND

INVERTING

REGULATOR

420kHz/2.1MHz

PROGRAMMING

LOGIC &

NV MEMORY

INN

I²C

LXN

MAX25221/B

ADD

GND

SCL SDA

VPROG

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Maxim Integrated | 2

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

TABLE OF CONTENTS

General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Benefits and Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Simplified Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Absolute Maximum Ratings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Package Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

TQFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

TQFN-SW. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Typical Operating Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Pin Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

MAX25220 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

MAX25221/B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Functional Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

MAX25220 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

MAX25221/B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Detailed Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Power-Up state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Switching Frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Stand-Alone Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

2

I C Read-Only Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Source Driver Power Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Gate-Driver Power Supplies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Sequencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Sequencing Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

VCOM Buffer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

VCOMN Negative Power Supply. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Limiting the Range of VCOM Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

VCOM Temperature Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

NTC Connection Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Internal Temperature Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Temperature Compensation Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Fault Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Undervoltage Faults on the Source, Gate and VCOM Outputs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Thermal Warning and Shutdown. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

NV Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Auto-Refresh Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

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Maxim Integrated | 3

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

TABLE OF CONTENTS (CONTINUED)

BURN, REBOOT and RESTART Commands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

2

I C Interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

2

I C Slave Addresses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Parity Checking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Register Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

MAX25220/MAX25221/MAX25221B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Register Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Applications Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Boost Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Boost Converter Inductor Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Boost Output Filter Capacitor Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Boost Input Filter Capacitor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Setting the AVDD Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

NAVDD Inverting Regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

NAVDD Regulator Inductor Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

NAVDD External Diode Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

NAVDD Output Capacitor Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Setting the VG

and VG

Output Voltages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

OFF

ON

VG

Voltage Higher than Three Times AVDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

ON

4x Charge Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

VCOM Block. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

VCB Transistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

VCOM Temperature Compensation Example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Sample VCOM Temperature Compensation Curve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Using the NV Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Layout Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Typical Application Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

MAX25220 Applications Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

MAX25221 Applications Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

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Maxim Integrated | 4

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

LIST OF FIGURES

Figure 1. Sequencing Example (Sequence 1, Not to Scale). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 2. Possible NTC Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Figure 3. Temperature Compensation Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 4. Quadrupler Charge-Pump at 2.1MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Figure 5. Sample VCOM Temperature Compensation Curve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

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Maxim Integrated | 5

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

LIST OF TABLES

Table 1. DEVICE BEHAVIOR AFTER START-UP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Table 2. Available Sequences. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 3. VCOM Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Table 4. FLTB Duty Cycle in Stand-Alone Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

2

Table 5. I C Slave Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Table 6. ADC Result vs Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Table 7. VCOM Setting Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

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Maxim Integrated | 6

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Absolute Maximum Ratings

IN, INN to GND......................................................... -0.3V to +6V

IN to INN................................................................ -0.3V to +0.3V

V18 to GND ........................................................... -0.3V to +2.2V

HVINP to GND.......................................................... -0.3V to 16V

LXP, AVDD to GND.................................. -0.3V to HVINP + 0.3V

BST to GND............................................................ -0.3V to +16V

BST to LXP............................................................ -0.3V to +2.2V

LXN to INN ............................................................. -22V to +0.3V

PGND, CPGND, DGND to GND............................ -0.3V to +0.3V

VCB to GND .......................................... V18 - 22V to V18 + 0.3V

VCOMN to GND....................................... V18 - 6V to V18 + 0.3V

PGVDD, FC1-, FC2-, DN to GND.............-0.3V to HVINP + 0.3V

FC1+ to GND .......................................... -0.3V to PGVDD + 0.3V

FC2+ TO FC1+ .......................................................-0.3V to +22V

VG

to FC2+ ........................................................-0.3V to +22V

ON

FC2+, VG

to GND ..............................................-0.3V to +24V

ON

EN, FLTB, SCL, SDA to GND...................................-0.3V to +6V

ADD, TEMP, R to GND .......................... -0.3V to V18 + 0.3V

REF

V

PROG

to GND .......................................................-0.3V to +14V

Continuous Power Dissipation (Multilayer Board) (T = +70ºC,

A

VG

, NAVDD to GND ............................. IN - 22V to IN + 0.3V

derate 21.3mW/ºC above +70ºC) ...................................2222mW

Operating Temperature Range.............................-40°C to 125°C

OFF

VCOM to GND.................................. VCOMN - 0.3V to IN + 0.3V

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the

device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for

extended periods may affect device reliability.

Package Information

TQFN

Package Code

T3255+6C

21-0140

90-0603

Outline Number

Land Pattern Number

Thermal Resistance, Single-Layer Board:

Junction to Ambient (θ

)

47°C/W

3°C/W

JA

Junction to Case (θ

)

JC

Thermal Resistance, Four-Layer Board:

Junction to Ambient (θ

)

36°C/W

3°C/W

JA

Junction to Case (θ

)

JC

TQFN-SW

Package Code

Outline Number

T3255Y+6C

21-100041

90-100066

Land Pattern Number

Thermal Resistance, Single-Layer Board:

Junction to Ambient (θ

)

47°C/W

3°C/W

JA

Junction to Case (θ

)

JC

Thermal Resistance, Four-Layer Board:

Junction to Ambient (θ

)

36°C/W

3°C/W

JA

Junction to Case (θ

)

JC

For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-” in the package code indicates

RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status.

Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board. For detailed information on package thermal

considerations, refer to www.maximintegrated.com/thermal-tutorial.

www.maximintegrated.com

Maxim Integrated | 7

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Electrical Characteristics

(V = 3.3V, V

IN

= 3.3V, Limits are 100% guaranteed between T = -40°C and T = +125°C. )

INN

A A

PARAMETER

INPUT SUPPLY

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

IN Voltage Range

IN UVLO Threshold

2.65

2.4

5.5

V

IN_UVLO_R

Rising

2.5

2.57

IN_UVLO_HY

S

IN UVLO Hysteresis

100

mV

IN Shutdown Current

IN Quiescent Current

V18 REGULATOR

V18 Output Voltage

V18 Current Limit

I

EN = GND, V = 3.3V, T = 25°C

7

12

µA

IN_SHDN

IN

A

I

V

EN

= V = 3.3V, no switching.

1.5

2.5

mA

IN_Q

IN

1.72

60

1.8

1.88

1.7

V

mA

V18 Undervoltage

Lockout

V18 rising

1.6

1.65

150

V

V18 Undervoltage

Hysteresis

mV

OSCILLATOR

f

bit = 0, dither disabled. Switching

SW

f

frequency for boost, inverter, and charge

pumps.

1950

385

2100

2250

455

BOOSTH

Operating Frequency

kHz

%

f

bit = 1, dither disabled. Switching

SW

f

frequency for boost, inverter, and charge

pumps.

420

±6

BOOSTL

f

BOOSTD

Frequency Dither

BOOST REGULATOR

HVINP Output Voltage

Range

V

+ 1

10.5

V

HVINP

IN

AVDD Output Voltage

Range

4.2

AVDD Adjustment Step

Size

0.1

6.8

AVDD Output

Regulation

avdd[5:0] = 0x1A, full load current and

input voltage range

V

6.664

6.936

AVDD

420kHz switching frequency

2.1MHz switching frequency

87

84

88.5

87

90

Oscillator Maximum

Duty Cycle

%

Low-Side Switch On-

Resistance

LXP_RON_LS

I

= 0.1A

0.1

0.2

Ω

LXP

Synchronous Rectifier

On-Resistance

Synchronous Rectifier

Zero-Crossing

Threshold

ZX_TH

70

2

mA

LXP Leakage Current

LXP Current Limit

LXP_L_LEAK

V

= 0V, V

= 10.5V

LXP

20

µA

A

EN

I

Duty cycle = 50%

1.7

2.3

LIMPH

www.maximintegrated.com

Maxim Integrated | 8

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Electrical Characteristics (continued)

(V = 3.3V, V

IN

= 3.3V, Limits are 100% guaranteed between T = -40°C and T = +125°C. )

INN

A A

PARAMETER

Soft-Start Period

SYMBOL

CONDITIONS

Current-limit ramp

MIN

TYP

MAX

UNITS

t

5

ms

BOOST_SS

INVERTING REGULATOR

2.1MHz switching frequency

INV_MAXDC 420kHz switching frequency

92

88

95

90

Oscillator Maximum

Duty Cycle

%

V

= 2.65V to 5.5V, V

= 6.8V,

AVDD

INN

V

+ V

V

AVDD

NAVDD

NAVDD_AVD

D_REG

1mA < I

load as NAVDD

< 200mA, I

= same

-34

0

34

mV

NAVDD

AVDD

Regulation Voltage

LXN On-Resistance

LXN Leakage Current

LXN_RON

INN to LXN, I

= 0.1A

0.25

0.5

20

Ω

LXN

V

IN

= 3.6V, V

= V

= -6.8V, T

NAVDD A

LXN_LEAK

µA

= +25°C

LXN Current Limit

Soft-Start Period

I

Duty cycle = 80%

Current-limit ramp

1.55

1.9

5

2.25

A

LIMNH

t

ms

INV_SS

NAVDD Discharge

Resistance

2

kΩ

V

POSITIVE CHARGE-PUMP REGULATOR

VG Threshold for

ON

V

-

HVINP

0.8

Charge-Pump Switching

Enable

FC1-, FC2- Switches

Current Limit, High-side

90

72

120

100

4

mA

Ω

FC1-, FC2- Switches

Current Limit, Low-side

FC1-, FC2- to CPGND

On-Resistance

6.5

FC1-, FC2- to HVINP

On-Resistance

6

10.5

Ω

FC2+ to PGVDD, FC1+

to FC2+ and VG

FC1+ Switches On-

Resistance

to

ON

2.5

4.5

Ω

VG

I C Mode

Voltage Range,

ON

7.6

20.2

V

2

VG Adjustment Step

Size, I C Mode

ON

0.2

12

3

2

vgon[5:0] = 0x16, full load current and

> 5V, charge-pump tripler

VG

Output Voltage

V

VGON

11.7

2.2

12.3

3.8

V

ON

V

HVINP

VG

Resistance

Discharge

kΩ

NEGATIVE CHARGE-PUMP REGULATOR

DN Current Limit

75

100

mA

V

VG

2

Voltage Range,

OFF

-18.2

-5.6

I C Mode

www.maximintegrated.com

Maxim Integrated | 9

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Electrical Characteristics (continued)

(V = 3.3V, V

IN

= 3.3V, Limits are 100% guaranteed between T = -40°C and T = +125°C. )

INN

A A

PARAMETER

Adjustment Step

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

VG

OFF

0.2

V

2

Size, I C Mode

VG Output-Voltage

Accuracy

vgoff[5:0] = 0x16, full load current and

input voltage range, 420kHz operation.

OFF

-10.3

-10

6

-9.7

10

V

Ω

DN On-Resistance,

High-Side

DN On-Resistance,

Low-Side

I

= -10mA

3.5

1.5

6.5

Ω

DN

VG

Discharge

OFF

mA

Current

SEQUENCE SWITCHES

AVDD ON Resistance

AVDD Current Limit

Between HVINP and AVDD, I

200mA

=

AVDD

R

0.5

1

Ω

mA

kΩ

Ω

ONAVDD

ILIM

300

80

600

POS

AVDD Discharge

Resistance

1.2

6

PGVDD On resistance

PGVDD Current Limit

(HVINP-PGVDD), I

= 3mA

9

PGVDD

Expires when PGVDD charging is

completed

100

mA

FAULT PROTECTION

Fault Timeout

tfault[1:0] = 10

60

1.9

1

ms

s

Fault Retry Time

tretry[1:0] = 10 or 11

Stand-alone mode only

FLTB Output Frequency

0.88

1.12

kHz

FLTB Output Duty

Cycle, VG

Fault

or VG

Stand-alone mode only

75

50

%

ON

OFF

FLTB Output Duty Cycle

with AVDD, NAVDD or

HVINP Fault

Stand-alone mode only

FLTB Output Duty

Cycle, VCOM Fault

25

85

40

85

40

85

%

V

AVDD Undervoltage

Fault Threshold

Relative measurement between HVINP

and AVDD

80

35

80

35

80

90

45

90

45

90

AVDD Short-Circuit

Fault Threshold

Relative measurement between HVINP

and AVDD

NAVDD Undervoltage

Fault Threshold

Measured with respect to AVDD

Of set value

NAVDD Short-Circuit

Fault Threshold

VG

Undervoltage

ON

Fault Threshold

VG Short-Circuit

V

-

ON

HVINP

1.1

VG

Falling

ON

Fault Threshold

www.maximintegrated.com

Maxim Integrated | 10

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Electrical Characteristics (continued)

(V = 3.3V, V

IN

= 3.3V, Limits are 100% guaranteed between T = -40°C and T = +125°C. )

INN

A A

PARAMETER

Undervoltage

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

VG

OFF

Of set value

80

85

90

%

Fault Threshold

VG Short-Circuit

Fault Threshold

OFF

35

40

10

45

%

Short-Circuit and

Overload Fault Delay

µs

VCOM BUFFER

VCOMN Output Voltage

VCB Output Current

I

= 120mA, V

= -10.5V

NAVDD

-3.5

12

-3.2

21

V

VCOM

5

mA

VCOM Output Current

Limit, Sinking

Dynamic output current, t < t

120

200

70

300

85

mA

FAULT

VCOM Output Current

Limit, Sourcing

I

120

60

LIMCOMP

VCOM Overcurrent

Detection Threshold

of

I

LIMCOMP

VCOM Offset Voltage,

Complete Range

V

load

= -2.49V and V

= +1V, no

VCOM

-20

+20

mV

VCOM Offset Voltage,

25°C

T

= 25°C, VCOM = -0.5V

-6

+6

+10

1

mV

V

A

VCOM Offset Voltage

VCOM = -0.5V

Temperature compensation disabled

-10

VCOM Output Voltage

Range

-2.49

VCOM DAC Step Size

VCOM Buffer Slew Rate

VCOM Fault Threshold

6.83

0.72

+0.25

60

mV

V/μs

V

C

+1V

= 10nF, VCOM from -2.49V to

VCOM

Deviation from set voltage

tfault[1:0] = 10

VCOM Fault Detection

Filter Time

ms

VCOM Discharge

Resistance

to GND

9

0

14

22

kΩ

R

REF

INPUT

R

REF

Input Voltage

1.25

V

Range

R

ADC Resolution

Conversion Rate

4.88

128

625

mV

kHz

mV

REF

TEMP Voltage

V

TEMP

I

= 10 to 500μA

TEMP

TEMP Current Mirror

Gain

1

μA/μA

TEMP

Internal Temperature

Sensor Voltage

T

A

= 25°C

620

5

mV

R

REF

DAC Offset

www.maximintegrated.com

Maxim Integrated | 11

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Electrical Characteristics (continued)

(V = 3.3V, V

IN

= 3.3V, Limits are 100% guaranteed between T = -40°C and T = +125°C. )

INN

A A

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

mV

R

Error

DAC Full-Scale

REF

5

R

DAC Gain Error

DAC Differential

-0.4

+0.4

%

REF

0.5

LSB

Non-linearity

R

REF

DAC Integral Non-

LSB

Linearity

LOGIC INPUTS and OUTPUTS (EN, SCL, ADD, SDA)

EN Glitch Filter

EN_BLK

10

µs

EN Minimum Low Time

For Reset

C

V18

= 1uF

1

ms

EN Input Logic-High

EN Input Logic-Low

ADD Input Logic-High

ADD Input Logic-Low

1.22

V

0.6

1.22

0.66

12

ADD Input Pulldown

Current

10

μA

V

SCL, SDA Input, Logic-

High

1.22

-1

SCL, SDA Input, Logic-

Low

0.6

+1

V

SCL Input Leakage

Current

µA

V

FLTB, SDA Output Low

Voltage

V

Sinking 5mA

5.5V

0.4

+1

OL

FLTB, SDA Output

Leakage Current

I

-1

µA

LEAK

PROGRAMMING VOLTAGE

V

Voltage

8.2

8.5

8

8.8

8.2

V

PROG

V

rising

falling

PROG

Undervoltage Threshold

V

PROG

Voltage

8.8

9

V

PROG

Overvoltage Threshold

VPROG Input Current

NV Programming Time

THERMAL SHUTDOWN

During NV programming, T = 25°C

9

25

20

mA

ms

A

16

Thermal Warning

Threshold

125

160

15

°C

Thermal-Shutdown

Threshold

T

SHDN

Thermal-Shutdown

Hysteresis

T

SHDN_HYS

www.maximintegrated.com

Maxim Integrated | 12

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Electrical Characteristics (continued)

(V = 3.3V, V

IN

= 3.3V, Limits are 100% guaranteed between T = -40°C and T = +125°C. )

INN

A A

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

2

I C INTERFACE

Clock Frequency

f

0.4

MHz

ns

SCL

Hold Time (Repeated)

START

t

600

HD:STA

SCL Low Time

SCL High Time

t

1300

600

ns

LOW

t

HIGH

Setup Time (Repeated)

START

t

600

ns

SU:STA

HD:DAT

Data Hold Time

Data Setup Time

t

0

ns

t

100

SU:DAT

Setup Time for STOP

Condition

t

600

ns

SU:STO

Spike Suppression

50

Note 1: Note 1: Limits are 100% tested at T = +25°C. Limits over the operating temperature range and relevant supply voltage range

A

are guaranteed by design and characterization.

www.maximintegrated.com

Maxim Integrated | 13

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Typical Operating Characteristics

(V = +3.3V, F

IN

= 2.1MHz, T = +25 C unless otherwise noted.)

SW

A

www.maximintegrated.com

Maxim Integrated | 14

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Typical Operating Characteristics (continued)

(V = +3.3V, F

IN

= 2.1MHz, T = +25 C unless otherwise noted.)

SW

A

www.maximintegrated.com

Maxim Integrated | 15

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Pin Configurations

MAX25220

TOP VIEW

24 23 22 21 20 19 18 17

25

26

27

28

29

30

31

32

16

DN

AVDD

15

14

13

12

11

10

9

HVINP

LXP

SDA

SCL

FLTB

I.C.

PGND

BST

MAX25220

GND

V18

I.C.

DGND

NAVDD

+

ADD

1

2

3

4

5

6

7

8

TQFN

5mm x 5mm

www.maximintegrated.com

Maxim Integrated | 16

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

MAX25221/B

TOP VIEW

24 23 22 21 20 19 18 17

25

26

27

28

29

30

31

32

16

DN

AVDD

15

14

13

12

11

10

9

HVINP

LXP

SDA

SCL

FLTB

PGND

BST

MAX25221/B

RREF

TEMP

DGND

NAVDD

GND

V18

+

ADD

1

2

3

4

5

6

7

8

TQFN

5mm x 5mm

Pin Description

NAME

FUNCTION

MAX25220

MAX25221/B

Programming Voltage. Apply a voltage of 8.5V to this pin during the programming

of non-volatile registers. Connect to GND through a resistor during normal

operation.

1

V

PROG

2

3

2

3

LXN

INN

IC

DC-DC Inverting Converter Inductor/Diode Connection.

Inverting Converter Input. Connect 10μF + 0.1μF ceramic capacitors from this pin

to ground for proper operation.

4

—

4

Internally connected. Leave this pin open.

Drive Output for External npn Pass Transistor for VCOMN regulator. Connect to

the base of the external npn transistor.

—

VCB

5

—

6

—

5

IC

VCOM

IC

Internally Connected. Leave this pin open.

Output of VCOM amplifier.

—

Internally Connected. Connect this pin to GND.

Negative Supply for VCOM Buffer. Connect a ceramic capacitor of at least 1μF

from VCOMN to GND.

—

7

6

7

VCOMN

IN

Supply Connection for Display Bias Circuitry. Bypass IN with local 10μF and 0.1μF

capacitors.

www.maximintegrated.com

Maxim Integrated | 17

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Pin Description (continued)

NAME

FUNCTION

MAX25220

MAX25221/B

Enable Input Pin. When EN is low, the device is in shutdown. When EN is taken

high, the device is active. In stand-alone mode, the outputs are turned on in the

stored sequence when EN goes high.

8

EN

2

Device Address Select pin. Connect to GND or V18 to Select the Device I C

2

Address. See the I C address table. To use stand-alone mode (without I C) leave

the ADD pin open. In this mode, the device turns on all outputs in the programmed

sequence when EN is taken high.

9

ADD

10

11

10

11

V18

Output of Internal 1.8V Regulator. Connect a 1μF capacitor from V18 to GND.

Ground Connection

GND

Bootstrap Capacitor Connection for Synchronous Rectifier Driver. Connect a

0.1μF ceramic capacitor between BST and LXP.

12

13

14

15

16

12

13

14

15

16

BST

PGND

LXP

Ground Connection for Boost Switching Device and VCOM Buffer. Connect to

GND using a low-impedance trace.

Switching Node of Boost Converter. Connect the boost inductor between LXP and

IN.

Boost Output and Input to Positive and Negative Charge-Pump Drivers. Bypass

HVINP with a 10μF output capacitor placed close to the pin.

HVINP

AVDD

Switched Output of Boost Converter. Connect a bypass capacitor of value 2.2μF

from AVDD to PGND.

Supply Voltage for Positive Charge Pump. PGVDD is connected to HVINP by

means of an internal switch when the positive charge pump is enabled. Bypass

PGVDD with a ceramic capacitor of 1μF to GND.

17

PGVDD

Positive Connection for Second Flying Capacitor. Connect a 22nF capacitor from

FC2- to FC2+.

18

19

20

21

18

19

20

21

FC2+

FC2-

FC1+

FC1-

Negative Connection for Second Flying Capacitor. Connect a 22nF capacitor from

FC2- to FC2+.

Positive Connection for First Flying Capacitor. Connect a 22nF capacitor from

FC1- to FC1+.

Negative Connection for First Flying Capacitor. Connect a 22nF capacitor from

FC1- to FC1+.

Output of Positive Charge-Pump Block. Connect a 1μF capacitor from VG

GND.

to

ON

22

23

24

22

23

24

VG

ON

CPGND

VG

Ground Connection for Charge Pumps.

Output of Negative Charge-Pump Block. Connect a 1μF capacitor from this pin to

GND.

OFF

25

26

27

25

26

27

DN

Negative Charge-Pump Push-Pull Drive Output.

2

SDA

SCL

Bidirectional I C Data Pin.

2

I C Clock Pin.

Open-Drain, Active-Low Fault Output. Connect a pullup resistor from FLTB to a

logic supply ≤5V. In stand-alone mode, the duty cycle of the FLTB pin indicates an

error condition, if present (see Table 4). When the serial interface is used, FLTB is

either a 0 (indicating data to be read from the internal registers) or a 1.

28

29

28

—

FLTB

IC

Internally Connected. Leave this pin open.

www.maximintegrated.com

Maxim Integrated | 18

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Pin Description (continued)

NAME

FUNCTION

MAX25220

MAX25221/B

Reference Resistor Pin. When using the temperature compensation function,

—

30

—

31

32

29

—

30

31

32

R

REF

connect a resistor from R

to GND. If unused, leave R

unconnected.

REF

IC

Internally Connected. Leave this pin open.

Temperature Sensor Pin. When using the temperature compensation function,

connect an NTC from TEMP to GND. If unused, leave TEMP unconnected.

TEMP

DGND

NAVDD

Logic Ground.

Negative Source-Driver Output Voltage. Connect ceramic capacitors of value

0.1μF and 10μF from this pin to GND with the smallest capacitor closest to the pin.

www.maximintegrated.com

Maxim Integrated | 19

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Functional Diagrams

MAX25220

IN

V18

REG

BST

TFT BOOST

CONTROL

420kHz/2.1MHz

PGVDD

FC2+

HVINP

LXP

FC2-

PGND

POSITIVE

CHARGE PUMP

FC1+

FC1-

0.9V

TEMP

WARNING,

SHUTDOWN

HVINP

AVDD

VGON

REFERENCE

POSITIVE

SOFT-START

AND

VGOFF

DN

DISCHARGE

ENABLE, CONTROL

AND FAULT LOGIC

NEGATIVE

CHARGE PUMP

NEGATIVE

SOFT-START

AND

NAVDD

DISCHARGE

CPGND

EN

FLTB

DGND

INVERTING

REGULATOR

420kHz/2.1MHz

PROGRAMMING

LOGIC &

NV MEMORY

INN

I²C

LXN

MAX25220

ADD

GND

SCL SDA

VPROG

www.maximintegrated.com

Maxim Integrated | 20

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Functional Diagrams (continued)

MAX25221/B

RREF TEMP

V18

IN

DAC

REG

VCOM

8b ADC FOR

TEMP

COMPENSATION

VCOMN

BST

NAVDD

NEG.

REGULATOR

VCB

PGVDD

FC2+

TFT BOOST

CONTROL

UVLO

HVINP

420kHz/2.1MHz

LXP

FC2-

PGND

POSITIVE

CHARGE PUMP

FC1+

0.9V

TEMP

WARNING,

SHUTDOWN

FC1-

HVINP

AVDD

VGON

REFERENCE

POSITIVE

SOFT-START

AND

VGOFF

DN

DISCHARGE

ENABLE, CONTROL

AND FAULT LOGIC

NEGATIVE

CHARGE PUMP

NEGATIVE

SOFT-START

AND

NAVDD

DISCHARGE

CPGND

EN

FLTB

DGND

INVERTING

REGULATOR

420kHz/2.1MHz

PROGRAMMING

LOGIC &

NV MEMORY

INN

I²C

LXN

MAX25221/B

ADD

GND

SCL SDA

VPROG

www.maximintegrated.com

Maxim Integrated | 21

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Detailed Description

The MAX25220/MAX25221/MAX25221B are 4-channel TFT-LCD power ICs that provide symmetrical positive AVDD

and negative NAVDD supplies as well as VG and V gate supplies. In addition, a VCOM buffer with output

ON

GOFF

voltage range above and below ground and a temperature-measurement block are integrated in the MAX25221 and

MAX25221B.

The devices contain non-volatile memory so that the values of all outputs can be calibrated for the lifetime of the device.

2

Programming is carried out using the built-in I C interface, which can also be used to read back diagnostic information.

Operation in stand-alone mode is also possible.

The temperature-sensor interface block in the MAX25221 and MAX25221B determines the temperature by measuring

the voltage on the R

pin when a temperature-sensitive component, such as an NTC, is connected to TEMP. The

REF

VCOM output voltage can be adjusted as a function of the measured temperature.

Power-Up state

When power is applied, the MAX25220/1 are in low-quiescent-current mode until the EN pin is taken high. When EN is

taken high (if the device supply voltage on IN exceeds the undervoltage lockout voltage of 2.5V) the 1.8V regulator is

turned on and the device is functional after a delay of 1ms. Subsequent operation depends on the device configuration

and type as follows:

Table 1. DEVICE BEHAVIOR AFTER START-UP

DEVICE

ADD = 0

ADD PIN FLOATING

ADD = V18

MAX25220/ Outputs turned on when start bit in

Outputs turned on

Outputs turned on when start bit in

1

register REG_CTRL is written to 1.

immediately when EN high. register REG_CTRL is written to 1.

Outputs turned on Outputs turned on immediately when EN

immediately when EN high. high.

Outputs turned on immediately when EN

high.

MAX25221B

If the non-volatile memory has been written to previously the stored values are read and the outputs are turned on in the

programmed sequence. If the device has not been programmed previously it powers up with the default voltages of 6.8V

(AVDD), 12V (VG ) and -10V (VG

ON

).

OFF

2

When I C is used, all values can be programmed and the outputs turned on using the start bit in the REG_CTRL register.

The values can subsequently be stored in non-volatile memory using the burn_otp command, if required.

If at any time the internal 1.8V regulator is out of range, the v18oor bit is set in register FAULT2 and the FLTB pin is

2

asserted low, assuming the device is being used in I C mode. No other action is taken unless the V18 voltage is below

its undervoltage lockout level.

Switching Frequency

The switching frequency of the boost and inverting converters and the charge pumps is set using the f

bit in register

SW

CONFIG. When f

is 0, the switching frequency is 2.1MHz. When f

is set to 1, the switching frequency is 420kHz.

SW

The switching frequency can have spread-spectrum applied to improve EMI performance using the en_ss bit in register

CONFIG.

Stand-Alone Operation

Stand-alone operation is used when the device has already been programmed and should start up with the pre-

programmed values when power is applied and the EN pin taken high. In stand-alone mode, leave the ADD pin

unconnected.

2

I C Read-Only Mode

The MAX25221B starts up immediately with the pre-programmed values when power is applied and the EN pin taken

2

high. If the ADD pin is connected to V18 the I C interface is in read-only mode and can only be used to read the device

registers, writing is not possible. The 7-bit I2C address of the device is 0x29 (0x53 when the read bit is added) in this

www.maximintegrated.com

Maxim Integrated | 22

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

mode.

Source Driver Power Supplies

The source-driver power supplies consist of a boost converter with output switch and an inverting buck-boost converter

that generate up to +10.5V maximum and down to -10.5V minimum, respectively, and can deliver up to 200mA on the

positive regulator and -200 mA on the negative regulator. The positive source-driver power supply’s regulation voltage

2

(AVDD) is set by writing the avdd[5:0] value in the AVDD_SET register using the I C interface, and can be programmed

into non-volatile memory. The default AVDD output voltage is 6.8V.

The negative source-driver supply voltage (NAVDD) is automatically tightly regulated to -AVDD within ±34mV. NAVDD

cannot be adjusted independently of AVDD.

The AVDD boost converter is a current-mode converter with two internal switches and internal compensation. The direct

output of the converter is HVINP while AVDD is a switched-output version. The NAVDD converter is a current-mode

converter with one internal switch, an external diode and internal compensation.

Gate-Driver Power Supplies

The positive gate-driver power supply (VG ) is a regulated charge-pump tripler and generates up to +20.2V. Note also

ON

that the maximum output voltage is 3 x AVDD - R

x I

x K, where R

is typically 30Ω and K is a

ONTOTAL

VGON

ONTOTAL

factor 0.75. In cases where a doubler charge pump is sufficient, set the cp_2stage bit and leave pins FC1- and FC1+

unconnected in order to increase efficiency.

The negative gate-driver power supply (VG

) generates a maximum negative voltage of -18.2V and requires external

OFF

diodes and capacitors. The VG

and VG

blocks switch at the same frequency as the AVDD and NAVDD converters.

OFF

ON

Both supplies are capable of output currents up to 15mA, assuming sufficient headroom. The VG

regulation voltages are set by writing the vgon[5:0] and vgoff[5:0] values in the register map using the I C interface, and

can be stored in the non-volatile section of the register map.

and VG

OFF

ON

2

Sequencing

The power-on and power-off sequences are controlled by the seq_set[2:0] bits in the VCOM_L register. The setting

should be written before the sequence is to be executed and should not be changed during the turn-on or turn-off

sequences. The sequence options are as follows:

Table 2. Available Sequences

POWER-OFF (REVERSE-ORDER

SEQUENCE SET BITS

POWER-ON

OF POWER-ON)

2nd 3rd

after t3 after t2 after t1

NOTES

2nd

3rd

4th

Sequence

No.

seq_set2 seq_set1 seq_set0 1st

after t1 after t2 after t3 1st

ms

VG

/

VGON/

ON

1

2

3

4

5

6

0

1

0

1

0

1

0

1

0

1

AVDD

NAVDD VG

VG

NAVDD AVDD

OFF

ON

OFF

ON

VCOM VCOM

VG VG

VCOM VCOM

/

OFF

VG

VG VG

VCOM VCOM

/

ON

Default

setting

ON

NAVDD AVDD

VG

AVDD

NAVDD

OFF

ON

VG VG

VCOM VCOM

/

OFF

VGON

AVDD

VG VGON/

VCOM VCOM

/

ON

NAVDD VG

AVDD

VG

OFF

ON

OFF

ON

AVDD/ AVDD/

VCOM VCOM

VG

NAVDD

NAVDD VG

VG

OFF

www.maximintegrated.com

Maxim Integrated | 23

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Table 2. Available Sequences (continued)

AVDD/

NAVDD

VG

VCOM

/

VG

VCOM

/

ON

AVDD/

NAVDD

ON

7

1

0

VG

-

VG

-

OFF

AVDD/

NAVDD

VG

VCOM

/

VG

VCOM

/

OFF

AVDD/

NAVDD

OFF

8

1

VG

VGON

ON

The times in the above table are determined by the delayt1, delayt2 and delayt3 settings in the DELAY-VCOM_LSB

register. The fastest power-up is obtained by setting the delays to 0.

The output voltages are not monitored during off sequencing; each output is turned off in turn using the programmed

delays. When the delays are set to zero, outputs are turned off in sequence with 1ms delays .A sequence can be stored

in non-volatile memory by writing to the burn_otp_reg register.

The V18 linear regulator is powered down 200ms after the power-down sequence is complete. After this time, the device

is in shut-down mode and can be restarted by setting the EN input high.

Sequencing Diagram

VGON

t_{BOOST_SS}

AVDD

EN

0V

1ms

VCOM

delayt3

delayt2

delayt1

delayt2

delayt3

NAVDD

VGOFF

t_{INV_SS}

Figure 1. Sequencing Example (Sequence 1, Not to Scale)

VCOM Buffer

2

The VCOM output voltage is programmed using I C to a value between -2.49V and +1V. The 9-bit value can also be

stored in non-volatile memory. The most-significant bits of the VCOM voltage setting are in the VCOM25 register while

the least-significant bit is the vcom25_0 bit in the DELAY-DELAYVCOM_LSB register.

The VCOM buffer can output peak currents up to ±120mA. If the VCOM output voltage deviates from the set value by

more than 0.25V, a VCOM fault is detected and flagged with the vcom_flt bit in the FAULT2 register. When this fault is

detected, the VCOM buffer continues to function—it is not automatically disabled. Note that a fault condition can lead to

high power dissipation in the VCOM buffer and could lead to thermal shutdown of the entire device. If the VCOM buffer is

continuously in current limit for more than the time set by tfault[1:0], it is disabled together with the AVDD, NAVDD, VG

H

and VG outputs to avoid damage to the IC. Also in this case the vcom_flt bit is set.

L

The maximum capacitive load on the VCOM output is 10nF. If higher capacitance loads are used, a series resistor should

be employed to maintain stability.

To calculate the value to write to the VCOM25 register use the following equation:

www.maximintegrated.com

Maxim Integrated | 24

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

V

+ 2.49

COM

VCOM25 =

0.00683

The correspondence between the VCOM set value and the VCOM voltage is shown in table 2.

Table 3. VCOM Settings

VCOM25 REGISTER VALUE

VCOM VOLTAGE (V)

0x1FF

0x1FE

...

1

0.9932

...

0x16E

0x16D

0x16C

...

+0.0098

+0.003

-0.0039

...

0x002

0x001

0x000

-2.4763

-2.4832

-2.49

VCOMN Negative Power Supply

A linear regulator is implemented to derive a regulated -3.5V for the VCOM buffer from the NAVDD supply.The npn

transistor connected to the VCB pin acts as the pass transistor of the regulator. The peak output current of the regulator

is the same as the peak negative drive current from the VCOM output, or at least 120mA. The device senses the voltage

at VCOMN and regulates it to -3.5V by driving VCB. The peak drive current for the base of the external npn is at least

5mA.

Limiting the Range of VCOM Voltage

When temperature compensation is not enabled, it is possible to limit the excursion of VCOM to a range between the

values set in the VCOM_MIN and VCOM_MAX registers. If an attempt is made to write a value outside the set range to

2

VCOM25, the VCOM output voltage is not updated and the I C interface issues a NACK.

VCOM Temperature Compensation

The VCOM output voltage can be compensated for temperature changes using a temperature-sensitive component (e.g.

an NTC thermistor) connected to the TEMP input or an internal temperature sensor. Select the sensor to be used with

the int_sensor bit in the CONFIG register (the default configuration is to use the external sensor). The TEMP pin is forced

to 625mV and the current drawn from it is mirrored on the R

pin. The voltage generated due to the resistor on R

REF

is fed to the internal 8-bit ADC, which has a reference voltage of 1.25V. The input to the ADC is therefore as follows:

0.625 × R

RREF

V

=

ADC

R

TEMP

With reference to Figure 2: R

= (R

| | R1) + R2

NTC

TEMP

The highly non-linear NTC characteristic can be modified depending on which temperature (cold, room, or hot)

necessitates the highest resolution. As an example in Figure 2, a reference resistor is connected to R while a

REF

combination of the NTC and two low-TC resistors R1 and R2 are connected to TEMP. In this way, an ADC reading that is

steeper at higher temperatures is obtained, enhancing the resolution of the ADC there. When temperature compensation

is enabled, the value of the voltage on the R

pin is available in the TEMP (0x01) register.

REF

Temperature compensation is enabled by setting the T_comp_en bit in the DELAY-VCOM_LSB register. When

T_comp_en is high, the voltage on the R pin is measured and the VCOM output voltage is updated at a rate of 1Hz.

REF

At start-up, even with temperature compensation enabled, there is a delay before compensation becomes active due to

the time needed to sample the temperature. For this reason, the device always starts up with the VCOM25 voltage value

on VCOM.

www.maximintegrated.com

Maxim Integrated | 25

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

The VCOM value at 25°C is the value written in the VCOM25 register together with the LSB from DELAY-VCOM_LSB

register. This value serves as the reference for all other VCOM values. The 5-bit values in the VCOM_L, and VCOM_H1

registers represent the change in VCOM from the VCOM25 value at the temperature represented by an ADC reading of

VTEMP_L and VTEMP_H1. The value in the VCOM_H2 register represents the positive shift in VCOM from VCOM_H1.

The VCOM_L value represents a negative shift in VCOM while VCOM_H1 and VCOM_H2 represent positive shifts.

NTC Connection Diagram

V18

1.25V

DAC

TEMP

SENSOR

ADC

0.625V

8

TEMP

RREF

T

R1

R2

Figure 2. Possible NTC Connection

Internal Temperature Sensor

The internal temperature sensor senses the junction temperature of the IC which may be significantly different from

the ambient temperature. To use the internal sensor, set the int_sensor bit in the CONFIG register to 1. The internal

temperature sensor has a temperature coefficient of 2mV/°C and a nominal output voltage of 620mV at 25°C.

When the internal temperature sensor is selected, it is connected directly to the ADC input at RREF.

www.maximintegrated.com

Maxim Integrated | 26

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Temperature Compensation Curve

1V

VCOM (V)

ADC READING

VCOM_H2

VCOM_H1

VCOM_L

-1V

VCOM25

-2V

-2.49V

Figure 3. Temperature Compensation Curve

Fault Handling

2

The reaction to faults is dependent on whether the device is in I C or stand-alone mode.

2

In I C mode, the following faults, if not masked, cause the FLTB pin to assert low: avdd_uv, navdd_uv, vgon_uv,

vgoff_uv, vcom_flt, nv_flt, th_shdn, vin_uvlo, and par_err. The th_warn fault is masked by default and must be explicitly

enabled using the th_warn_mask bit.

2

When the ADD pin is left floating (I C interface not used) the FLTB pin outputs a pulse train of varying duty cycle

depending on the detected fault as shown in Table 4.

Table 4. FLTB Duty Cycle in Stand-Alone Mode

DUTY-CYCLE

FAULT

or VG

75%

VG

fault

OFF

ON

50%

25%

AVDD, NAVDD or HVINP fault

VCOM fault

0% (continuously low)

NV fault or thermal shutdown

The frequency at the FLTB pin is 1kHz when indicating a fault. If multiple faults are present, the highest-priority fault is

indicated. The list above is in order of priority with the highest priority listed last.

Undervoltage Faults on the Source, Gate and VCOM Outputs

When an undervoltage is detected on any of the AVDD, NAVDD, VG , or VG

outputs, all of the outputs are turned

OFF

ON

off and the appropriate fault bit is set in the FAULT1 register. At the same time, the FLTB pin asserts low. Depending on

the setting of the tretry[1:0] bits, the subsequent behavior of the device is as follows:

● tretry = 01, 10 or 11: After 0.95s or 1.9s a retry is performed where all outputs are turned on in the appropriate

sequence. If the fault is still present, the output will be disabled again after tfault[1:0]. A total of three retries are

performed, after which no further retry attempts are performed (the device can be restarted by toggling power or the

EN pin or by using the RESTART command). If tretry = 11 retries continue until the fault is removed and normal

www.maximintegrated.com

Maxim Integrated | 27

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

function can resume.

● tretry = 00: No retry is attempted (the device can be restarted by toggling power or the EN pin or by using the

RESTART command).

If a short-circuit is encountered during start-up, device operation is halted, all outputs are disabled, and the subsequent

behavior depends on the setting of retry[1:0] as described above. The short-circuit checks on VG

enabled 1ms after the pins are enabled.

and VG

are

OFF

ON

During retry, faults are no longer monitored and the fault or faults which caused retry are indicated using the

corresponding fault bits. During retry, the FLTB pin asserts low unless the fault which caused the retry is masked.

Thermal Warning and Shutdown

When the junction temperature reaches 125°C, the thermal warning bit is set. The device takes no further action.

If the device junction temperature reaches 160°C, all outputs are turned off immediately. When the junction temperature

drops by 15°C, the outputs are re-enabled using the stored sequence.

NV Memory

The MAX25220/MAX25221/MAX25221B include five blocks of one-time-programmable memory. The user can store the

block of volatile registers from 0x07 to 0x15 in non-volatile memory which is in turn mapped to register locations 0x17 to

0x25. Note that before the non-volatile memory has been programmed, a read from the locations 0x17 to 0x25 yields the

result 0xFF.

The contents of the non-volatile memory are protected by a single-error correction/double-error detection (SECDED)

redundant code while data transfer from non-volatile memory to registers 0x07 to 0x15 is protected by a parity check. If

the parity check fails, a retry is performed two times. If all three attempts are unsuccessful, the device does not start up,

the nv_flt bit is set, and the FLTB pin is asserted low. If the SECDED check fails, the device does not start up, the nv_flt

bit is set, and the FLTB pin is asserted low.

If there are no errors, the outputs are turned on with the stored values and in the stored sequence.

To store the contents of registers 0x07 to 0x15 to non-volatile memory a voltage source of 8.5V ±2% capable of supplying

2

more than 25mA should be connected to the V

pin. When the V

voltage is stable an I C NV write command

PROG

can be performed by writing to the burn_otp_reg register. If the NV write is unsuccessful (because the V

voltage

PROG

was out of range or because of a general memory error) the nv_flt bit is set, FLTB pin goes low. After an NV write

command is executed, the nv_flt bit should be checked. If nv_flt is high another NV write can be attempted.

Connect V

to GND if non-volatile memory is not used.

PROG

Ensure that temperature compensation is disabled when programming VCOM.

Auto-Refresh Function

When the refresh bit in register CONFIG is set, the device reads from the non-volatile registers at intervals of 1s and

writes the data into the corresponding volatile registers. This avoids the effect of possible corruption of the volatile

registers. Auto-refresh reads are subject to error correction in the same way as the initial read after device power-up.

When programming the non-volatile memory, the auto-refresh function should be enabled immediately before performing

the burn_otp_reg write. See the section Using the NV Memory in Applications Information.

BURN, REBOOT and RESTART Commands

The BURN and REBOOT commands are used to store the contents of registers 0x07 to 0x15 in non-volatile memory

or to fetch the contents of non-volatile memory and load them into registers 0x07 to 0x15, respectively. The RESTART

command is used to restart the device from a latched-fault mode. When a RESTART command is performed, all fault bits

are cleared.

A BURN command is performed by writing to register address 0x78 (burn_otp_reg).

A REBOOT command is performed by writing to register address 0x79 (reboot_otp_reg).

A RESTART command is performed by writing to register address 0x7A (soft_restart).

www.maximintegrated.com

Maxim Integrated | 28

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

When parity checking is enabled and one of these user commands is sent to the device, the third byte should be such as

to have even parity over the 3 bytes sent.

2

I C Interface

2

The MAX25220/MAX25221/MAX25221B include an I C, 2-wire serial interface consisting of a serial-data line (SDA) and

a serial-clock line (SCL). SDA and SCL facilitate communication between the IC and the master at clock rates up to

400kHz. The master, typically a microcontroller, generates SCL and initiates data transfer on the bus.

The Slave ID of the MAX25220/MAX25221/MAX25221B depends on the connection of the ADD pin according to Table

4.

A master device communicates with the MAX25220/MAX25221/MAX25221B by transmitting the correct Slave ID with

appended R/W bit, followed by the register address and data word (for a write transaction only). Each transmit sequence

is framed by a START (S) or Repeated START (Sr) condition, and a STOP (P) condition. Each word transmitted over the

bus is 8 bits long and is always followed by an acknowledge clock pulse.

The IC's SDA line operates as both an input and an open-drain output. A pullup resistor greater than 1kΩ is required on

the SDA bus. In general, the resistor should be selected as a function of bus capacitance such that the rise time on the

bus is not greater than 120ns. The IC's SCL line operates as an input only. A pullup resistor greater than 1kΩ is required

on SCL if there are multiple masters on the bus, or if the master in a single-master system has an open-drain SCL output.

In general, for the SCL-line resistor selection, the same recommendations as for SDA apply. Series resistors in line with

SDA and SCL are optional. The SCL and SDA inputs suppress noise spikes to assure proper device operation even on

a noisy bus.

2

I C Slave Addresses

2

Table 5. I C Slave Addresses

DEVICE ADDRESS

WRITE

ADDRESS

READ

ADDRESS

ADD PIN CONNECTION

A6

0

A5

1

A4

0

A3

0

A2

0

A1

0

A0

1

GND

V18

0x42

0x43

0x53

0

1

0

1

0

1

0x52*

* On the MAX25221B writing to the device is not possible when ADD is connected to V18.

Parity Checking

Even parity checking for write transactions can be enabled by setting the par_en bit in REG_CTRL to 1. The parity bit is

the most-significant bit of the register address byte and should be set to attain even parity. The parity check is performed

over all 3 bytes received by the device: the slave address, the register address, and the data payload. Burst-mode write

2

is not supported when parity checking is enabled; a complete I C transaction is needed to write to each single register.

2

When a parity bit error is detected the par_err bit is set, the I C interface issues a NACK and no write is performed.

When writing any of the BURN, REBOOT, and RESTART commands, parity must be adjusted by changing the third or

payload byte; the command byte must not be changed.

www.maximintegrated.com

Maxim Integrated | 29

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Register Map

MAX25220/MAX25221/MAX25221B

ADDRESS

NAME

MSB

LSB

USER REGISTERS

0x00

0x01

0x02

DEVICE[7:0]

TEMP[7:0]

–

dev_id[5:0]

temp[7:0]

REG_CTRL[7:0]

FLTMASK1[7:0]

par_en

–

start

–

rev_id[2:0]

–

avdd_uv

_mask

navdd_u

v_mask

vgon_uv

_mask

vgoff_uv

_mask

0x03

0x04

–

par_err_ vin_uvlo hvinp_uv

vcom_flt th_warn_

_mask

FLTMASK2[7:0]

–

mask

avdd_uv

par_err

refresh

_mask

mask

navdd_u

v

0x05

0x06

0x07

FAULT1[7:0]

FAULT2[7:0]

CONFIG[7:0]

–

vgon_uv

nv_flt

–

vgoff_uv

th_warn

v18oor

vin_uvlo hvinp_uv th_shdn

en_ss fSW

delayt2[1:0]

vcom25[7:0]

vcom_flt

int_sens

or

tretry[1:0]

delayt3[1:0]

tfault[1:0]

DELAY-

VCOM_LSB[7:0]

T_comp_ vcom25_

en

0x08

delayt1[1:0]

0

0x09

0x0A

0x0B

0x0C

0x0D

0x0E

0x0F

0x10

0x11

0x12

0x13

VCOM25[7:0]

VCOM_L[7:0]

seq_set[2:0]

vcom_l[4:0]

VCOM_H1[7:0]

VCOM_H2[7:0]

VTEMP25[7:0]

VTEMP_L[7:0]

VTEMP_H1[7:0]

VTEMP_H2[7:0]

VCOM_MIN[7:0]

VCOM_MAX[7:0]

AVDD_SET[7:0]

–

vcom_h1[4:0]

vcom_h2[4:0]

vtemp25[7:0]

vtemp_l[7:0]

vtemp_h1[7:0]

vtemp_h2[7:0]

vcom_min[7:0]

vcom_max[7:0]

–

avdd[5:0]

cp_2stag

e

0x14

0x15

0x17

VGON[7:0]

vgon[5:0]

vgoff[5:0]

VGOFF[7:0]

–

nv_int_s nv_refres nv_en_s

ensor

NV_CONFIG[7:0]

nv_fSW

nv_retry[1:0]

nv_tfault[1:0]

h

s

NV_DELAY-

VCOM_LSB[7:0]

nv_T_co nv_vcom

0x18

nv_delayt1[1:0]

nv_delayt2[1:0]

nv_delayt3[1:0]

mp_en

25_0

0x19

0x1A

0x1B

0x1C

0x1D

0x1E

0x1F

NV_VCOM25[7:0]

NV_VCOM_L[7:0]

NV_VCOM_H1[7:0]

NV_VCOM_H2[7:0]

NV_VTEMP25[7:0]

NV_VTEMP_L[7:0]

NV_TEMP_H1[7:0]

nv_vcom25[7:0]

nv_seq_set[2:0]

nv_vcom_l[4:0]

–

nv_vcom_h1[4:0]

nv_vcom_h2[4:0]

–

nv_vtemp25[7:0]

nv_vtemp_l[7:0]

nv_vtemp_h1[7:0]

www.maximintegrated.com

Maxim Integrated | 30

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

ADDRESS

0x20

NAME

MSB

LSB

NV_TEMP_H2[7:0]

NV_VCOM_MIN[7:0]

NV_VCOM_MAX[7:0]

NV_AVDD_SET[7:0]

nv_vtemp_h2[7:0]

0x21

nv_vcom_min[7:0]

0x22

nv_vcom_max[7:0]

0x23

–

nv_avdd[5:0]

nv_vgon[5:0]

nv_vgoff[5:0]

nv_cp_2

stage

0x24

0x25

NV_VGON[7:0]

NV_VGOFF[7:0]

–

USER COMMANDS

0x78

0x79

0x7A

burn_otp_reg[7:0]

burn_otp[7:0]

reboot_otp_reg[7:0]

soft_restart[7:0]

reboot_otp[7:0]

soft_restart[7:0]

Register Details

DEVICE (0x00)

BIT

Field

7

–

6

–

5

4

3

2

1

0

dev_id[5:0]

Reset

Access

Type

–

Read Only

BITFIELD

BITS

DESCRIPTION

dev_id

5:0

Device ID. Reads 0x20/21

TEMP (0x01)

BIT

7

6

5

4

3

2

1

Field

temp[7:0]

0x0

Reset

Access

Type

Read Only

BITFIELD

BITS

DESCRIPTION

pin.

temp

7:0

Voltage reading from R

REF

REG_CTRL (0x02)

BIT

7

6

5

–

4

–

3

–

2

1

Field

par_en

0x0

start

0x0

rev_id[2:0]

0x1

Reset

Access

Type

Write, Read Write, Read

–

Read Only

BITFIELD

BITS

DESCRIPTION

Parity enable bit. When 1 this bit enables parity checking on write transactions

to the device.

par_en

7

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Maxim Integrated | 31

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

BITFIELD

BITS

DESCRIPTION

Enable bit. When this bit is set to 1 the turn-on sequence set using the

seq_set bits is executed. The default value of this bit is 0 except in the

MAX25221B where it is 1.

start

6

rev_id

2:0

Revision ID. Reads 0x1.

FLTMASK1 (0x03)

BIT

7

–

6

5

–

4

3

–

2

1

–

0

avdd_uv_m

ask

navdd_uv_

mask

vgon_uv_m

ask

vgoff_uv_m

ask

Field

Reset

0x0

Access

Type

Write, Read

BITFIELD

BITS

DESCRIPTION

avdd_uv_mask

6

When 1 this bit prevents an undervoltage on AVDD from asserting FLTB low.

When 1 this bit prevents an undervoltage on NAVDD from asserting FLTB

low.

navdd_uv_mask

vgon_uv_mask

vgoff_uv_mask

4

2

0

When 1 this bit prevents an undervoltage on VGON from asserting FLTB low.

When 1 this bit prevents an undervoltage on VGOFF from asserting FLTB

low.

FLTMASK2 (0x04)

BIT

7

–

6

5

4

3

–

2

–

1

0

par_err_ma vin_uvlo_m hvinp_uv_m

vcom_flt_m th_warn_ma

Field

sk

ask

sk

Reset

0x0

0x1

Access

Type

Write, Read Write, Read Write, Read

Write, Read Write, Read

BITFIELD

par_err_mask

BITS

DESCRIPTION

6

5

When 1 prevents parity errors from asserting the FLTB pin.

vin_uvlo_mask

When 1 this bit prevents an undervoltage on IN from asserting the FLTB pin.

Mask bit for hvinp_uv diagnostic. When 1 an undervoltage on HVINP does not

cause FLTB to assert.

hvinp_uv_mask

vcom_flt_mask

th_warn_mask

4

1

0

When 1 this bit prevents a fault on VCOM from asserting FLTB low.

When 1 this bit prevents an overtemperature warning from asserting FLTB

low.

FAULT1 (0x05)

BIT

Field

7

–

6

5

–

4

3

–

2

1

–

0

avdd_uv

0x0

navdd_uv

0x0

vgon_uv

0x0

vgoff_uv

0x0

Reset

Access

Type

Read

Clears All

Read

Clears All

Read

Clears All

Read

Clears All

–

BITFIELD

BITS

DESCRIPTION

avdd_uv

6

When 1 this bit indicates an undervoltage on AVDD.

www.maximintegrated.com

Maxim Integrated | 32

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

BITFIELD

navdd_uv

BITS

DESCRIPTION

4

2

0

When 1 this bit indicates an undervoltage on NAVDD.

vgon_uv

vgoff_uv

When 1 this bit indicates an undervoltage on VG

.

ON

.

OFF

FAULT2 (0x06)

BIT

Field

7

6

5

4

3

2

1

0

v18oor

0x0

par_err

0x0

vin_uvlo

0x0

hvinp_uv

0x0

th_shdn

0x0

nv_flt

0x0

vcom_flt

0x0

th_warn

0x0

Reset

Access

Type

Read

Clears All

Read

Clears All

Read

Clears All

Read

Clears All

Read

Clears All

Read

Clears All

Read

Clears All

Read

Clears All

BITFIELD

v18oor

BITS

DESCRIPTION

Indicates that the 1.8V output is out of range, either above its overvoltage

level or below its undervoltage level.

7

6

2

par_err

Indicates that a parity error was detected on an I C transaction.

Indicates an undervoltage condition on the IN pin. When this happens the

device turns off all outputs and waits for IN to return above the IN UVLO level,

after which the outputs are re-enabled in the programmed sequence.

vin_uvlo

5

hvinp_uv

th_shdn

4

3

When 1 this bit indicates an undervoltage on the boost output, HVINP.

When 1 this bit indicates an overtemperature shutdown.

Non-volatile memory failure - unsuccessful transfer of the contents of NV

memory to working memory or more than one error detected.

nv_flt

2

When 1 indicates a fault on the VCOM output either due to it being 0.25V

away from its set value (unfiltered) or because the VCOM buffer was in

vcom_flt

th_warn

1

0

current limit for a time t

.

fault

When 1 this bit indicates a thermal warning.

CONFIG (0x07)

BIT

7

6

5

4

3

2

1

0

Field

int_sensor

0x0

refresh

0x0

en_ss

0x0

fSW

0x0

tretry[1:0]

0x1

tfault[1:0]

0x0

Reset

Access

Type

Write, Read Write, Read Write, Read Write, Read

Write, Read

BITFIELD

BITS

DESCRIPTION

DECODE

Set this bit to 1 to use the internal

temperature sensor.

int_sensor

refresh

7

When this bit is 1 the contents of the NV

registers are automatically copied to the

volatile registers every second.

0x0: Refresh disabled.

0x1: Refresh enabled.

6

Enable spread-spectrum by setting this bit to

1.

en_ss

fSW

5

4

0x0: 2.1MHz

0x1: 420kHz

Sets switching frequency.

0x0: Retry disabled

0x1: Retry after 0.95s, total 3 retries.

0x2: Retry after 1.9s, total 3 retries.

0x3: Retry after 1.9s

tretry

3:2

Sets retry time after a fault.

www.maximintegrated.com

Maxim Integrated | 33

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

BITFIELD

BITS

DESCRIPTION

DECODE

0x0: 15ms

0x1: 30ms

0x2: 60ms

0x3: 90ms

tfault

1:0

Sets fault delay time.

DELAY-VCOM_LSB (0x08)

BIT

Field

7

6

5

4

3

2

1

0

delayt1[1:0]

0x2

delayt2[1:0]

0x2

delayt3[1:0]

0x2

T_comp_en

0x0

vcom25_0

0x0

Reset

Access

Type

Write, Read

Write, Read Write, Read

BITFIELD

BITS

DESCRIPTION

Set delay t1 in the start-up sequence. Choose between 0, 5ms, 10ms and

15ms.

delayt1

delayt2

delayt3

7:6

Set delay t2 in the start-up sequence. Choose between 0, 5ms, 10ms and

15ms.

5:4

3:2

Set delay t3 in the start-up sequence. Choose between 0, 5ms, 10ms and

15ms.

When 1 this bit enables temperature compensation of the output of the VCOM

amplifier.

T_comp_en

vcom25_0

1

0

LSB of VCOM setting at 25°C.

VCOM25 (0x09)

BIT

Field

7

6

5

4

3

2

1

0

vcom25[7:0]

0x0

Reset

Access

Type

Write, Read

BITFIELD

BITS

DESCRIPTION

vcom25

7:0

VCOM setting at 25°C.

VCOM_L (0x0A)

BIT

Field

7

6

5

4

3

2

1

0

seq_set[2:0]

0x2

vcom_l[4:0]

0x00

Reset

Access

Type

Write, Read

BITFIELD

BITS

DESCRIPTION

DECODE

0x0: Sequence 1.

0x1: Sequence 2.

0x2: Sequence 3.

0x3: Sequence 4.

0x4: Sequence 5.

0x5: Sequence 6.

0x6: Sequence 7.

0x7: Sequence 8.

seq_set

7:5

Sequence selection bits.

www.maximintegrated.com

Maxim Integrated | 34

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

BITFIELD

BITS

DESCRIPTION

DECODE

Delta VCOM at at the temperature

corresponding to VTEMP_L. This value sets

the difference between the VCOM value at

25°C and that at VTEMP_L.

vcom_l

4:0

VCOM_H1 (0x0B)

BIT

Field

7

–

6

–

5

–

4

3

2

1

0

vcom_h1[4:0]

0x00

Reset

Access

Type

–

Write, Read

BITFIELD

BITS

DESCRIPTION

Delta VCOM at VTEMP_H1. This value sets the difference between the

VCOM value at 25°C and that at VTEMP_H1.

vcom_h1

4:0

VCOM_H2 (0x0C)

BIT

Field

7

–

6

–

5

–

4

3

2

1

0

vcom_h2[4:0]

0x0

Reset

Access

Type

–

Write, Read

BITFIELD

BITS

DESCRIPTION

Delta VCOM at VTEMP_H2. This value sets the difference between the

VCOM value at VTEMP_H1 and that at VTEMP_H2.

vcom_h2

4:0

VTEMP25 (0x0D)

BIT

Field

7

6

5

4

3

2

1

0

vtemp25[7:0]

0x0

Reset

Access

Type

Write, Read

BITFIELD

BITS

DESCRIPTION

vtemp25

7:0

Voltage at TEMP pin at 25°C.

VTEMP_L (0x0E)

BIT

Field

7

6

5

4

3

2

1

0

vtemp_l[7:0]

0x0

Reset

Access

Type

Write, Read

BITFIELD

BITS

DESCRIPTION

Voltage at TEMP pin corresponding to low-temperature breakpoint in VCOM

compensation curve.

vtemp_l

7:0

www.maximintegrated.com

Maxim Integrated | 35

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

VTEMP_H1 (0x0F)

BIT

Field

7

6

5

4

3

2

1

0

vtemp_h1[7:0]

Reset

0x0

Access

Type

Write, Read

BITFIELD

BITS

DESCRIPTION

Voltage at TEMP pin corresponding to first high-temperature breakpoint in

VCOM compensation curve.

vtemp_h1

7:0

VTEMP_H2 (0x10)

BIT

Field

6

5

4

3

2

1

0

vtemp_h2[7:0]

Reset

0x0

Access

Type

Write, Read

BITFIELD

BITS

DESCRIPTION

Voltage at TEMP pin corresponding to second high-temperature breakpoint in

VCOM compensation curve.

vtemp_h2

7:0

VCOM_MIN (0x11)

BIT

Field

6

5

4

3

2

1

0

vcom_min[7:0]

Reset

0x0

Access

Type

Write, Read

BITFIELD

BITS

DESCRIPTION

vcom_min

7:0

Lower limit for VCOM setting.

VCOM_MAX (0x12)

BIT

Field

7

6

4

3

2

vcom_max[7:0]

Reset

0xFF

Access

Type

Write, Read

BITFIELD

BITS

DESCRIPTION

vcom_max

7:0

Upper limit for VCOM setting.

AVDD_SET (0x13)

BIT

Field

7

–

6

–

4

3

2

avdd[5:0]

0x1A

Reset

Access

Type

–

Write, Read

www.maximintegrated.com

Maxim Integrated | 36

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

BITFIELD

BITS

DESCRIPTION

DECODE

0x0: 4.2

0x1: 4.3

0x2: 4.4

0x3: 4.5

0x4: 4.6

0x5: 4.7

0x6: 4.8

0x7: 4.9

0x8: 5

0x9: 5.1

0xA: 5.2

0xB: 5.3

0xC: 5.4

0xD: 5.5

0xE: 5.6

0xF: 5.7

0x10: 5.8

0x11: 5.9

0x12: 6

0x13: 6.1

0x14: 6.2

0x15: 6.3

0x16: 6.4

0x17: 6.5

0x18: 6.6

0x19: 6.7

0x1A: 6.8

0x1B: 6.9

0x1C: 7V

0x1D: 7.1

0x1E: 7.2

0x1F: 7.3

0x20: 7.4

0x21: 7.5

0x22: 7.6

0x23: 7.7

0x24: 7.8

0x25: 7.9

0x26: 8

avdd

5:0

Sets AVDD and NAVDD voltages.

0x27: 8.1

0x28: 8.2

0x29: 8.3

0x2A: 8.4

0x2B: 8.5

0x2C: 8.6

0x2D: 8.7

0x2E: 8.8

0x2F: 8.9

0x30: 9

0x31: 9.1

0x32: 9.2

0x33: 9.3

0x34: 9.4

0x35: 9.5

0x36: 9.6

0x37: 9.7

0x38: 9.8

www.maximintegrated.com

Maxim Integrated | 37

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

BITFIELD

BITS

DESCRIPTION

DECODE

0x39: 9.9

0x3A: 10

0x3B: 10.1

0x3C: 10.2

0x3D: 10.3

0x3E: 10.4

0x3F: 10.5

VGON (0x14)

BIT

7

–

6

5

4

3

2

1

0

Field

cp_2stage

0x0

vgon[5:0]

0x16

Reset

Access

Type

–

Write, Read

BITFIELD

BITS

DESCRIPTION

DECODE

Set this bit to 1 when using a two-stage

charge-pump.

cp_2stage

6

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Maxim Integrated | 38

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

BITFIELD

BITS

DESCRIPTION

DECODE

0x0: 7.6

0x1: 7.8

0x2: 8

0x3: 8.2

0x4: 8.4

0x5: 8.6

0x6: 8.8

0x7: 9

0x8: 9.2

0x9: 9.4

0xA: 9.6

0xB: 9.8

0xC: 10

0xD: 10.2

0xE: 10.4

0xF: 10.6

0x10: 10.8

0x11: 11

0x12: 11.2

0x13: 11.4

0x14: 11.6

0x15: 11.8

0x16: 12

0x17: 12.2

0x18: 12.4

0x19: 12.6

0x1A: 12.8

0x1B: 13

0x1C: 13.2

0x1D: 13.4

0x1E: 13.6

0x1F: 13.8

0x20: 14

vgon

5:0

Sets VG

voltage.

ON

0x21: 14.2

0x22: 14.4

0x23: 14.6

0x24: 14.8

0x25: 15

0x26: 15.2

0x27: 15.4

0x28: 15.6

0x29: 15.8

0x2A: 16

0x2B: 16.2

0x2C: 16.4

0x2D: 16.6

0x2E: 16.8

0x2F: 17

0x30: 17.2

0x31: 17.4

0x32: 17.6

0x33: 17.8

0x34: 18

0x35: 18.2

0x36: 18.4

0x37: 18.6

0x38: 18.8

www.maximintegrated.com

Maxim Integrated | 39

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

BITFIELD

BITS

DESCRIPTION

DECODE

0x39: 19

0x3A: 19.2

0x3B: 19.4

0x3C: 19.6

0x3D: 19.8

0x3E: 20

0x3F: 20.2

VGOFF (0x15)

BIT

Field

7

–

6

–

5

4

3

2

1

0

vgoff[5:0]

0x16

Reset

Access

Type

–

Write, Read

www.maximintegrated.com

Maxim Integrated | 40

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

BITFIELD

BITS

DESCRIPTION

DECODE

0x0: -5.6

0x1: -5.8

0x2: -6

0x3: -6.2

0x4: -6.4

0x5: -6.6

0x6: -6.8

0x7: -7

0x8: -7.2

0x9: -7.4

0xA: -7.6

0xB: -7.8

0xC: -8

0xD: -8.2

0xE: -8.4

0xF: -8.6

0x10: -8.8

0x11: -9

0x12: -9.2

0x13: -9.4

0x14: -9.6

0x15: -9.8

0x16: -10

0x17: -10.2

0x18: -10.4

0x19: -10.6

0x1A: -10.8

0x1B: -11

0x1C: -11.2

0x1D: -11.4

0x1E: -11.6

0x1F: -11.8

0x20: -12

0x21: -12.2

0x22: -12.4

0x23: -12.6

0x24: -12.8

0x25: -13

0x26: -13.2

0x27: -13.4

0x28: -13.6

0x29: -13.8

0x2A: -14

0x2B: -14.2

0x2C: -14.4

0x2D: -14.6

0x2E: -14.8

0x2F: -15

0x30: -15.2

0x31: -15.4

0x32: -15.6

0x33: -15.8

0x34: -16

0x35: -16.2

0x36: -16.4

0x37: -16.6

0x38: -16.8

vgoff

5:0

Sets VG

voltage.

OFF

www.maximintegrated.com

Maxim Integrated | 41

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

BITFIELD

BITS

DESCRIPTION

DECODE

0x39: -17

0x3A: -17.2

0x3B: -17.4

0x3C: -17.6

0x3D: -17.8

0x3E: -18

0x3F: -18.2

NV_CONFIG (0x17)

Non-volatile configuration register

BIT

7

6

5

4

3

2

1

0

nv_int_sens

or

Field

nv_refresh

nv_en_ss

nv_fSW

nv_retry[1:0]

nv_tfault[1:0]

Read Only

Reset

Access

Type

Read Only

BITFIELD

BITS

DESCRIPTION

DECODE

nv_int_senso

r

When this bit is 1 the internal temperature

sensor is used.

7

When this bit is 1 the contents of the NV

registers are automatically copied to the

volatile registers every second.

nv_refresh

6

When this bit is 1 spread-spectrum is

enabled.

nv_en_ss

nv_fSW

5

4

0x0: 2.2MHz

0x1: 440kHz

Sets switching frequency.

nv_retry

nv_tfault

3:2

1:0

Sets retry time after a fault.

NV_DELAY-VCOM_LSB (0x18)

BIT

7

6

5

4

3

2

1

0

nv_T_comp nv_vcom25

Field

nv_delayt1[1:0]

nv_delayt2[1:0]

nv_delayt3[1:0]

_en

0x0

_0

Reset

Access

Type

Read Only

BITFIELD

BITS

DESCRIPTION

Set delay t1 in the start-up sequence. Choose between 0, 5ms, 10ms and

15ms.

nv_delayt1

7:6

Set delay t2 in the start-up sequence. Choose between 0, 5ms, 10ms and

15ms.

nv_delayt2

5:4

3:2

1

Set delay t3 in the start-up sequence. Choose between 0, 5ms, 10ms and

15ms.

nv_delayt3

When 1 this bit enables temperature compensation of output of the VCOM

amplifier.

nv_T_comp_en

nv_vcom25_0

When 1 this bit enables temperature compensation of output of the VCOM

amplifier.

0

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Maxim Integrated | 42

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

NV_VCOM25 (0x19)

BIT

Field

7

6

5

4

3

2

1

0

nv_vcom25[7:0]

Reset

Access

Type

Read Only

BITFIELD

nv_vcom25

BITS

DESCRIPTION

7:0

VCOM setting at 25°C.

NV_VCOM_L (0x1A)

BIT

Field

7

6

5

4

3

2

1

0

nv_seq_set[2:0]

nv_vcom_l[4:0]

Reset

Access

Type

Read Only

BITFIELD

BITS

DESCRIPTION

nv_seq_set

nv_vcom_l

7:5

Sequence selection bits.

Delta VCOM at at the temperature corresponding to VTEMP_L. This value

sets the difference between the VCOM value at 25°C and that at VTEMP_L.

4:0

NV_VCOM_H1 (0x1B)

BIT

Field

7

–

6

–

5

–

4

3

2

1

0

nv_vcom_h1[4:0]

Reset

Access

Type

–

Read Only

BITFIELD

nv_vcom_h1

BITS

DESCRIPTION

Delta VCOM at VTEMP_H1. This value sets the difference between the

VCOM value at 25°C and that at VTEMP_H1.

4:0

NV_VCOM_H2 (0x1C)

BIT

Field

7

–

6

–

5

–

4

3

2

1

0

nv_vcom_h2[4:0]

Reset

Access

Type

–

Read Only

BITFIELD

nv_vcom_h2

BITS

DESCRIPTION

Delta VCOM at VTEMP_H2. This value sets the difference between the

VCOM value at VTEMP_H1 and that at VTEMP_H2.

4:0

www.maximintegrated.com

Maxim Integrated | 43

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

NV_VTEMP25 (0x1D)

BIT

Field

7

6

5

4

3

2

1

0

nv_vtemp25[7:0]

Reset

Access

Type

Read Only

BITFIELD

nv_vtemp25

BITS

DESCRIPTION

7:0

Voltage at TEMP pin at 25°C.

NV_VTEMP_L (0x1E)

BIT

Field

7

6

5

4

3

2

1

0

nv_vtemp_l[7:0]

Reset

Access

Type

Read Only

BITFIELD

nv_vtemp_l

BITS

DESCRIPTION

Voltage at TEMP pin corresponding to low-temperature breakpoint in VCOM

compensation curve.

7:0

NV_TEMP_H1 (0x1F)

BIT

Field

7

6

5

4

3

2

1

0

nv_vtemp_h1[7:0]

Reset

Access

Type

Read Only

BITFIELD

nv_vtemp_h1

BITS

DESCRIPTION

Voltage at TEMP pin corresponding to first high-temperature breakpoint in

VCOM compensation curve.

7:0

NV_TEMP_H2 (0x20)

BIT

Field

7

6

5

4

3

2

1

0

nv_vtemp_h2[7:0]

Reset

Access

Type

Read Only

BITFIELD

nv_vtemp_h2

BITS

DESCRIPTION

Voltage at TEMP pin corresponding to second high-temperature breakpoint in

VCOM compensation curve.

7:0

www.maximintegrated.com

Maxim Integrated | 44

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

NV_VCOM_MIN (0x21)

BIT

Field

7

6

5

4

3

2

1

0

nv_vcom_min[7:0]

Reset

Access

Type

Read Only

BITFIELD

nv_vcom_min

BITS

DESCRIPTION

7:0

Lower limit for VCOM setting.

NV_VCOM_MAX (0x22)

BIT

Field

7

6

4

3

2

nv_vcom_max[7:0]

Reset

Access

Type

Read Only

BITFIELD

nv_vcom_max

BITS

DESCRIPTION

7:0

Upper limit for VCOM setting.

NV_AVDD_SET (0x23)

BIT

Field

7

–

6

–

4

3

2

nv_avdd[5:0]

Reset

Access

Type

–

Read Only

BITFIELD

BITS

DESCRIPTION

nv_avdd

5:0

Sets AVDD and NAVDD voltages. See table for register 0x13.

NV_VGON (0x24)

BIT

7

–

6

4

3

2

1

nv_cp_2sta

ge

Field

nv_vgon[5:0]

Read Only

Reset

Access

Type

Read Only

BITFIELD

nv_cp_2stage

nv_vgon

BITS

6

DESCRIPTION

When this bit is set to 1 a two-stage charge-pump is used.

Sets VG voltage. See table for register 0x14.

5:0

ON

NV_VGOFF (0x25)

BIT

Field

7

–

6

–

5

4

3

2

1

0

nv_vgoff[5:0]

Read Only

Reset

Access

Type

–

www.maximintegrated.com

Maxim Integrated | 45

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

BITFIELD

nv_vgoff

BITS

5:0

DESCRIPTION

Sets VGOFF voltage. See table for register 0x15.

burn_otp_reg (0x78)

BIT

Field

7

6

5

4

3

2

1

0

burn_otp[7:0]

0x0

Reset

Access

Type

Write Only

BITFIELD

burn_otp

BITS

DESCRIPTION

Command to copy the contents of registers 0x07-0x15 to the non-volatile

registers 0x17-0x25.

7:0

reboot_otp_reg (0x79)

BIT

Field

7

6

4

3

2

1

0

reboot_otp[7:0]

Reset

Access

Type

Write Only

BITFIELD

reboot_otp

BITS

DESCRIPTION

Command to copy the contents of the non-volatile registers 0x17-0x15 to the

working registers 0x17-0x25.

7:0

soft_restart (0x7A)

BIT

Field

7

6

4

3

2

1

0

soft_restart[7:0]

0x00

Reset

Access

Type

Write Only

BITFIELD

BITS

DESCRIPTION

Command used to re-start the device from a latched fault mode. All faults are

cleared when this command is executed.

soft_restart

7:0

www.maximintegrated.com

Maxim Integrated | 46

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Applications Information

Boost Converter

Boost Converter Inductor Selection

Three key inductor parameters must be specified for operation with the device: Inductance value (L), inductor saturation

current (I ), and DC resistance (R ). To determine the inductance value, first select the ratio of inductor peak-to-

SAT

DC

peak ripple current to average output current (LIR). Higher LIR values mean higher RMS inductor current and therefore

2

higher I R losses. To achieve a lower LIR value, a high-valued inductor, which may be physically larger, must be used. A

good compromise between size and loss is to select a 30% to 60% peak-to-peak ripple current to average-current ratio

(LIR from 0.3 to 0.6). If extremely thin high-resistance inductors are used, as is common for LCD-panel applications, the

best LIR may lie between 0.5 and 1.0. The value of the inductor is determined below.

V

× D

IN

L =

LIR × I × f

IN SW

using:

V

× I

OUT OUT

I

=

IN

η × V

IN

V

IN

D = 1 −

V

OUT

where V is the input voltage, V

is the output voltage, I

is the output current, I is the calculated average boost

OUT IN

IN

OUT

input current, η is the efficiency of the boost converter, D is the duty cycle, and f

is either 420kHz or 2.1MHz (the

SW

selected switching frequency of the boost converter). The efficiency of the boost converter can be estimated from the

Typical Operating Characteristics and accounts for losses in the internal switch, inductor, and capacitors.

The inductor’s saturation rating must exceed the maximum current-limit of 2.3A.

Boost Output Filter Capacitor Selection

The primary criterion for selecting the output filter capacitor is low effective series resistance (ESR). The product of the

peak inductor current and the output filter capacitor’s ESR determine the amplitude of the high-frequency ripple seen

on the output voltage. For stability, the boost output-filter capacitor should have a value of 10μF or greater when using

2.1MHz switching.

To avoid a large drop on HVINP when AVDD is enabled, the capacitance on the HVINP node should be at least three

times larger than that on AVDD.

Boost Input Filter Capacitor

Sufficient input capacitance must be used to avoid input voltage drop when transients are encountered on the AVDD or

NAVDD outputs and when the AVDD switch is closed. If the IN voltage drops below 2.57V, the device is likely to reset so

input capacitance must prevent this. The total value of capacitance depends on the expected transients and the series

resistance in the IN connection. A good starting point is a total input capacitance of 2 x 22μF ceramic capacitors in parallel

with 2 x 10μF ceramic capacitors. Depending on the particular application circumstances more or less capacitance may

be needed.

Input capacitance requirements are significantly relaxed when an input voltage of 5V is used.

Setting the AVDD Voltage

The AVDD output voltage is set by writing a 6-bit value to the AVDD_SET register.

The NAVDD converter outputs a negative voltage whose absolute value is the same as AVDD.

NAVDD Inverting Regulator

www.maximintegrated.com

Maxim Integrated | 47

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

NAVDD Regulator Inductor Selection

The inductor value for the NEG regulator can be selected using the formula below.

V

× (1 − D)

NAVDD

L =

LIR × I

× f

NAVDD SW

where V

is the output voltage, I

the output current, LIR the desired inductor ripple ratio, and f

the

SW

NAVDD

switching frequency.

Calculate the duty-cycle D using:

V

NAVDD

D =

V

+ V

IN

NAVDD

The inductor's saturation current rating must exceed the maximum current-limit of 2.25A.

NAVDD External Diode Selection

Select a diode with a peak current rating of at least the LXN current limit (I

) for use with the NAVDD output.

LIMNH

The diode breakdown-voltage rating should exceed the sum of the maximum INN voltage and the absolute value of the

NAVDD voltage. A Schottky diode improves the overall efficiency of the converter but should be selected to have low

leakage at the maximum operating temperature.

NAVDD Output Capacitor Selection

The primary criterion for selecting the output filter capacitor is low ESR and capacitance value, as the NAVDD capacitor

provides the load current when the internal switch is on. The voltage ripple on the NAVDD output has two components:

1. Ripple to due ESR which is the product of the peak inductor current and the output filter capacitor’s ESR

2. Ripple due to bulk capacitance that can be determined as follows.

D

I

×

NAVDD

f

SW

ΔV

=

BULK

C

NAVDD

For stability, the NAVDD output capacitor should have a value of 10μF or greater when using 2.1MHz switching

frequency.

Setting the VG

and VG

Output Voltages

OFF

ON

The internal positive charge pump can output a voltage approximately three times AVDD. If a voltage of twice the HVINP

voltage is sufficient leave the FC1+ and FC1- pins unconnected and set the cp_2stage bit.

For V

the VG

, the number of charge-pump stages should be chosen to ensure sufficient output voltage while maintaining

voltage within its permitted operating range.

GOFF

OFF

The VG

output voltage is set by writing a 6-bit value to the vgon[5:0] field in the VG

register.

ON

voltage is set by writing a 6-bit value to the vgoff[5:0] field in the VG

register.

OFF

VG

Voltage Higher than Three Times AVDD

ON

In exceptional cases, it may be necessary to produce a VG

voltage greater than three times AVDD. In such cases,

ON

an external charge-pump circuit can be used as shown in Figure 4. When using the device in this way, leave the FC1-,

FC1+ and FC2+ pins unconnected and set the cp_2stage bit to 1.

www.maximintegrated.com

Maxim Integrated | 48

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

4x Charge Pump

PGVDD

1mF

470nF

22nF

MAX25220/1

470nF

FC2-

1mF

VGON

<4xV_AVDD

Figure 4. Quadrupler Charge-Pump at 2.1MHz

VCOM Block

VCB Transistor

Select an external npn transistor with a minimum current gain of 30. When designing the PCB, ensure that the parasitic

capacitance between the base and collector of the npn is minimized to avoid oscillation. Note that high continuous DC

current on VCOM causes very high power dissipation in the npn device and a device with low thermal resistance should

therefore be selected.

VCOM Temperature Compensation Example

Assume that an NTC with 10kΩ resistance at 25°C is connected from TEMP to GND and that the R

resistor is of

REF

value 2400Ω. At various temperatures, the following voltages will be observed on R

will be as follows:

and the ADC measurement result

REF

Table 6. ADC Result vs Temperature

TEMPERATURE

NTC RESISTANCE

R

VOLTAGE

ADC RESULT

0x02

DESIRED VCOM VOLTAGE

REF

-30°C

113kΩ

10kΩ

3kΩ

13mV

-1.09V

-1V

25°C

150mV

500mV

1V

0x1F

60°C

0x66

-0.98V

-0.91V

85°C

1.5kΩ

0xCD

The rightmost column of the previous table indicates the desired VCOM output voltage at each temperature, which will

be the inflection points in the temperature compensation curve. The following values are written to the relevant registers

(remembering that each LSB of the VCOM setting represents 6.83mV):

Table 7. VCOM Setting Example

REGISTER

FIELD

SETTING

0

NOTES

DELAYVCOM_LSB[7:0]

VCOM25

vcom25_0

vcom25[7:0]

vcom_l[4:0]

9-bit value is 011011010 or 0xDA which corresponds to -1V

Represents shift of -89mV from VCOM25

0x6D

0x0D

VCOM_L

www.maximintegrated.com

Maxim Integrated | 49

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Table 7. VCOM Setting Example (continued)

VCOM_H1

VCOM_H2

VTEMP25

VTEMP_L

VTEMP_H1

VTEMP_H2

vcom_h1[4:0]

vcom_h2[4:0]

vtemp25[7:0]

vtemp_l[7:0]

vtemp_h1[7:0]

vtemp_h2[7:0]

0x03

0x0A

0x1F

0x02

0x66

0xCD

Represents shift of +20mV from VCOM25

Represents shift of +68mV from VCOM_H1

ADC result at 25°C

ADC result at -30°C

ADC result at 60°C

ADC result at 85°C

With these settings, the VCOM output voltage at 25°C is -1V, while at the temperature represented by 13mV at the R

REF

pin the VCOM voltage decreases to -1.09V as set by the VCOM_L register. Similarly, the VCOM_H1 and VCOM_H2

values are output on VCOM when the TEMP voltage is 500mV and 1V, respectively. In between these values the device

interpolates the correct VCOM voltage value with a resolution of 6.83mV. The complete curve is shown in Figure 5.

When setting the values VTEMP_xx and VCOM_xx, it is important to avoid values which can cause wraparound in the

temperature compensation algorithm thus possibly leading to sudden changes in the value of VCOM.

Sample VCOM Temperature Compensation Curve

1V

VCOM (V)

1V

0xCD

13mV

0x02

150mV

0x1F

499mV

0x66

ADC READING

-0.91V

VCOM_H2

-0.98V

VCOM_H1

VCOM_L

-1.09V

-1V

VCOM25

-2V

-2.49V

Figure 5. Sample VCOM Temperature Compensation Curve

Using the NV Memory

Follow the sequence below to perform non-volatile programming of the device when the auto-refresh function is not used:

2

1. Apply a voltage between 3.3V and 5V to the IN and INN pins with the device in I C mode

2. Write the desired values to be stored in OTP to the registers from 0x07 to 0x15

3. Apply 8.5V to V

PROG

4. Optionally wait to ensure the 8.5V at V

is stable

PROG

5. Send burn_otp_reg (write any value to 0x78) command. If parity is enabled ensure the overall parity is even by

altering the final byte if necessary.

6. Wait 20ms

7. If the nv_flt bit is 0, the write was successful, go to next step. If nv_flt = 1, perform re-try (steps 5,6).

www.maximintegrated.com

Maxim Integrated | 50

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

8. Send reboot_otp (write any value to 0x79) command.

Special care is required when performing non-volatile programming with the auto-refresh feature enabled. In such cases

follow the sequence below when at least one calibration has already been performed:

1. Apply a voltage between 3.3V and 5V to the IN and INN pins

2. Write the desired values to be stored in NV memory to the registers from 0x07 to 0x15 (keep auto-refresh bit

disabled until here)

3. Enable the auto-refresh feature

4. Start polling one of the registers from 0x07 to 0x15 which has changed its value until that value gets refreshed to

the older one (auto-refresh is active)

5. The following steps from #6 to #10 must be completed within 1s

6. Write the desired values to be stored in OTP to the registers from 0x07 to 0x15 (including auto-refresh bit).

7. Apply 8.5V to V

PROG

8. Optionally wait to ensure the 8.5V at V

is stable

PROG

9. Send burn_otp_reg (write any value to 0x78) command. If parity is enabled ensure the overall parity is even by

altering the final byte if necessary

10. Wait 20ms

11. If the nv_flt bit is 0, the write was successful, go to next step. If nv_flt = 1, perform retry from step 2.

12. Send reboot_otp (write any value to 0x79) command

The non-volatile memory can be written to a total of 5 times.

Layout Considerations

The MAX25220/MAX25221/MAX25221B include high-frequency switching converters to generate the voltages for TFT-

LCDs. Take proper care while laying out the circuit board to ensure correct operation. The switching-converter portions

of the circuit have nodes with very fast voltage changes that could lead to undesirable effects on the sensitive parts of the

circuit as well as electromagnetic interference (EMI). Follow the guidelines below to reduce noise as much as possible:

● Connect the bypass capacitors on IN and INN as close as possible to the device and connect the capacitor ground to

the analog ground plane using vias close to the capacitor terminal. Ensure that the power connection to IN and INN

uses a very wide trace or complete board layer to avoid input undervoltage problems.

● Connect the GND pin of the device to the analog ground plane using a via close to GND. Lay the analog ground plane

on the inner layer, preferably next to the top layer. Use the analog ground plane to cover the entire area under critical

signal components for the power converter.

● Have a power-ground plane for the switching-converter power circuit under the power components (i.e., input filter

capacitor, output filter capacitor, inductor, MOSFET, rectifier diode, and current-sense resistor). Connect PGND to the

power-ground plane closest to PGND. Connect all other ground connections to the power ground plane using vias

close to the terminals.

● Minimize the copper area of all switching nodes to avoid EMI. Minimize the loop areas for the AVDD and NAVDD

converters by placing all components close to the LXP and LXN pins. Place the input and output capacitor grounds

close to each other. In the case of AVDD the input/output capacitor grounds should also connect directly to the PGND

pin.

● Connect GND, CPGND and PGND at the exposed pad of the device.

● Refer to the MAX25220/MAX25221/MAX25221B evaluation kit (EV kit) data sheet for a sample layout.

In addition, when using an external NTC temperature sensor for temperature compensation connect the grounded end

directly to the grounded end of the RREF resistor. This avoids possible differences in ground potential between different

points on the circuit board.

www.maximintegrated.com

Maxim Integrated | 51

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Typical Application Circuits

MAX25220 Applications Diagram

TFT POWER INPUT

10mF

IN

V18

FC2+

1mF

FC2-

FC1+

FC1-

PGVDD

VGON

1mF

TFT POWER INPUT

BST

VGOFF

DN

L3

LX

MAX25220

HVINP

10mF

PGND

AVDD

2.2mF

GND

EN

TFT POWER INPUT

INN

NAVDD

LXN

SDA

SCL

FLT

I²C BUS

FAULT OUTPUT

VPROG

EP

CPGND

DGND

ADD

10mF

www.maximintegrated.com

Maxim Integrated | 52

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Typical Application Circuits (continued)

MAX25221 Applications Diagram

TFT POWER INPUT

10mF

IN

PGVDD

V18

1mF

VCOM

FC2+

FC2-

0.1mF

VCOMN

VCB

FC1+

1mF

1kW

FC1-

VGON

NAVDD

TEMP

T

TFT POWER INPUT

BST

VGOFF

0.1mF

MAX25221/B

LX

DN

1mF

HVINP

10mF

RREF

PGND

AVDD

2.2mF

GND

EN

TFT POWER INPUT

INN

NAVDD

SDA

I²C BUS

SCL

FLT

LXN

FAULT OUTPUT

VPROG

EP

CPGND

DGND

ADD

10mF

www.maximintegrated.com

Maxim Integrated | 53

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Ordering Information

PART NUMBER

MAX25220ATJ/V+

MAX25221ATJ/V+

MAX25220ATJ/VY+

MAX25221ATJ/VY+*

MAX25221BATJ/V+

TEMPERATURE RANGE

PIN-PACKAGE

32 TQFN-EP

FEATURES

Without VCOM buffer

-40 to +125°C

32 TQFN-EP

With VCOM buffer

32 SWTQFN-EP

32 TQFN-EP

Without VCOM buffer

With VCOM buffer

EN pin turn-on, VCOM buffer

+ Denotes a lead(Pb)-free/RoHS-compliant package.

/V denotes an automotive qualified part.

Y = Side-wettable package.

T Denotes tape-and-reel.

*Future product - contact factory for availability.

www.maximintegrated.com

Maxim Integrated | 54

MAX25220/MAX25221/

MAX25221B

Automotive 4-Channel TFT-LCD Power Supply

with VCOM Buffer

Revision History

REVISION REVISION

PAGES

DESCRIPTION

CHANGED

NUMBER

DATE

5/20

6/20

0

1

2

Initial release

—

Removed future product notation from MAX25221ATJ/V+ in Ordering Information

Added Typical Operating Characteristics

54

14, 15

Updated Package Information and Electrical Characteristics; removed future product

notation for MAX25220ATJ/VY+ in Ordering Information

3

4

10/20

11/20

7, 11, 54

19, 54

Updated Pin Descriptions and Ordering Information.

For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html.

Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent

licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max

limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.

Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.


型号：	MAX25220ATJ
厂家：	MAXIM INTEGRATED PRODUCTS
描述：	Automotive 4-Channel TFT-LCD Power Supply with VCOM Buffer CD
文件：	总55页 (文件大小：722K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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