LM27965SQ/NOPB [TI]

具有 I2C 兼容亮度控制功能的双通道显示白光 LED 驱动器 | RTW | 24 | -30 to 85;


型号：	LM27965SQ/NOPB
厂家：	TEXAS INSTRUMENTS
描述：	具有 I2C 兼容亮度控制功能的双通道显示白光 LED 驱动器 \| RTW \| 24 \| -30 to 85 驱动驱动器
文件：	总25页 (文件大小：1346K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LM27965

www.ti.com

SNVS380B –MAY 2006–REVISED FEBRUARY 2013

LM27965 Dual Display White LED Driver with I2C Compatible Brightness Control

Check for Samples: LM27965

FEATURES

•

91% Peak LED Drive Efficiency

DESCRIPTION

The LM27965 is a highly integrated charge-pump-

based dual-display LED driver. The device can drive

up to 9 LEDs in parallel with a total output current of

180mA. Regulated internal current sinks deliver

excellent current and brightness matching in all LEDs.

•

No Inductor Required

0.3% Current Matching

Drives LEDs with up to 30mA per LED

180mA of total drive current

I²C Compatible Brightness Control Interface

Adaptive 1× - 3/2× Charge Pump

Resistor-Programmable Current Settings

External Chip RESET Pin

The LED driver current sinks are split into three

independently controlled groups. The primary group

can beconfigurabled with

LEDs, for

backlighting a larger main display and the second

group can be configured with 2 or 3 LEDs, for

backlighing

smaller secondary display. An

Extended Li-Ion Input: 2.7V to 5.5V

additional, independently controlled led driver is

provided for driving an indicator or general purpose

LED. The LM27965 has an I²C compatible interface

that allows the user to independently control the

brightness on each bank of LEDs.

Small low profile industry standard leadless

package, WQFN 24 : (4mm x 4mm x 0.8mm)

25mm²total solution size

Two I²C Compatible Chip Address Options:

0x36 for LM27965SQ and 0x38 for

LM27965SQ-M

•

The device provides excellent efficiency without the

use of an inductor by operating the charge pump in a

gain of 3/2, or in Pass-Mode. The proper gain for

maintaining current regulation is chosen based on

LED forward voltage, so that efficiency is maximized

over the input voltage range.

APPLICATIONS

•

Mobile Phone Display Lighting

PDA Backlighting

The LM27965 is available in a small 24-pin WQFN-24

package.

General LED Lighting

TYPICAL APPLICATION CIRCUIT

INDICATOR

LED

MAIN DISPLAY

SUB DISPLAY

D1C

D1A D2A D3A D4A D5A

D1B D2B D3B

OUT

1 mF

LM27965

1 mF

SET

GND

SCL

SET

I C

SDIO

VIO

Compatible

Interface

Capacitors: TDK C1608X5R1A105k ,

or equivalent

RESET

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

All trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

LM27965

SNVS380B –MAY 2006–REVISED FEBRUARY 2013

www.ti.com

CONNECTION DIAGRAM

24 Pin WQFN Package

See Package Number RTW0024A

DAP

18 17 16 15 14 13

Bottom View

13 14 15 16 17 18

Top View

Pin Functions

Pin Descriptions

Pin Name

V_IN

Pin No.

Pin Descriptions

Input voltage. Input range: 2.7V to 5.5V.

Charge Pump Output Voltage

P_OUT

C1, C2

19, 22 (C1)

20, 21 (C2)

Flying Capacitor Connections

D5A, D4A, D3A, D2A, 12, 13, 14, 15, 16 LED Drivers - GroupA

D1A

D1B, D2B, D3B

4, 5, 6

LED Drivers - GroupB

D1C

I_SET

LED Driver - Indicator LED

Placing a resistor (R_SET) between this pin and GND sets the full-scale LED current for DxA ,

DxB, and D1C LEDs.

Full-Scale LED Current = 200 × (1.25V ÷ R_SET

)

SCL

SDIO

VIO

Serial Clock Pin

Serial Data Input/Output Pin

Serial Bus Voltage Level Pin

RESET

GND

Harware Reset Pin. High = Normal Operation, Low = RESET

9, 18, DAP

8, 11

Ground

No Connect

These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam

during storage or handling to prevent electrostatic damage to the MOS gates.

Submit Documentation Feedback

Product Folder Links: LM27965

LM27965

www.ti.com

SNVS380B –MAY 2006–REVISED FEBRUARY 2013

(1) (2)(3)

Absolute Maximum Ratings

V_INpin voltage

-0.3V to 6.0V

SCL, SDIO, VIO,

RESET pin voltages

-0.3V to (V_IN+0.3V)

w/ 6.0V max

I_DxxPin Voltages

-0.3V to (V_POUT+0.3V)

w/ 6.0V max

Continuous Power Dissipation

Internally Limited

(4)

Junction Temperature (T_J-MAX

Storage Temperature Range

)

150ºC

-65ºC to +150º C

(5)

Maximum Lead Temperature (Soldering)

ESD Rating⁽⁶⁾

Human Body Model

2.0kV

(1) Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under

which operation of the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed

performance limits and associated test conditions, see the Electrical Characteristics tables.

(2) All voltages are with respect to the potential at the GND pins.

(3) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office / Distributors for

availability and specifications.

(4) Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at T_J= 170°C (typ.) and

disengages at T_J= 165°C (typ.).

(5) For detailed soldering specifications and information, please refer to National Semiconductor Application Note 1187: Leadless

Leadframe Package (AN-1187).

(6) The human body model is a 100pF capacitor discharged through 1.5kΩ resistor into each pin. (MIL-STD-883 3015.7)

(1) (2)

Operating Rating

Input Voltage Range

2.7V to 5.5V

2.0V to 4.0V

LED Voltage Range

Junction Temperature (T_J) Range

Ambient Temperature (T_A) Range⁽³⁾

-30°C to +100°C

-30°C to +85°C

(1) Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under

which operation of the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed

performance limits and associated test conditions, see the Electrical Characteristics tables.

(2) All voltages are with respect to the potential at the GND pins.

(3) In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may

have to be derated. Maximum ambient temperature (T_A-MAX) is dependent on the maximum operating junction temperature (T_J-MAX-OP

100°C), the maximum power dissipation of the device in the application (P_D-MAX), and the junction-to ambient thermal resistance of the

part/package in the application (θ_JA), as given by the following equation: T_A-MAX= T_J-MAX-OP– (θ_JA× P_D-MAX).

Thermal Properties

Junction-to-Ambient Thermal

Resistance (θ_JA), RTW0024A Package

41.3°C/W

(1)

(1) Junction-to-ambient thermal resistance is highly dependent on application and board layout. In applications where high maximum power

dissipation exists, special care must be paid to thermal dissipation issues in board design. For more information, please refer to National

Semiconductor Application Note 1187: Leadless Leadframe Package (AN-1187).

Electrical Characteristics^{(1) (2)}

Limits in standard typeface are for T_J= 25°C, and limits in boldface type apply over the full operating temperature range.

Unless otherwise specified: V_IN= 3.6V; V_RESET= V_IN; VIO = 1.8V V_DxA= V_DxB= V_DxC= 0.4V; R_SET= 12.7kΩ; BankA = BankB =

BankC = Fullscale Current; ENA, ENB, ENC, EN5A, EN3B Bits = “1”; C1 = C2 = C_IN= C_OUT= 1.0µF; Specifications related to

(3)

output current(s) and current setting pins (I_Dxxand I_SET) apply to BankA and BankB.

(1) All voltages are with respect to the potential at the GND pins.

(2) Min and Max limits are guaranteed by design, test, or statistical analysis. Typical numbers are not guaranteed, but do represent the

most likely norm.

(3) C_IN, C_POUT, C₁, and C₂: Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics

Submit Documentation Feedback

Product Folder Links: LM27965

LM27965

SNVS380B –MAY 2006–REVISED FEBRUARY 2013

www.ti.com

Electrical Characteristics^{(1) (2)}(continued)

Limits in standard typeface are for T_J= 25°C, and limits in boldface type apply over the full operating temperature range.

Unless otherwise specified: V_IN= 3.6V; V_RESET= V_IN; VIO = 1.8V V_DxA= V_DxB= V_DxC= 0.4V; R_SET= 12.7kΩ; BankA = BankB =

BankC = Fullscale Current; ENA, ENB, ENC, EN5A, EN3B Bits = “1”; C1 = C2 = C_IN= C_OUT= 1.0µF; Specifications related to

output current(s) and current setting pins (I_Dxxand I_SET) apply to BankA and BankB. ⁽³⁾

Symbol

Parameter

Condition

Min

Typ

Max

Units

Output Current Regulation

BankA or BankB Enabled

3.0V ≤ V_IN≤ 5.5V

ENA = '1' or ENB = '1' and ENC= '0'

18.2

(-9.5%)

22.0

(+9.5%)

(%)

20.1

Output Current Regulation

BankC Enabled

3.0V ≤ V_IN≤ 5.5V

ENC = '1' and ENA = ENB= '0'

19.2

(-7.7%)

22.4

(+7.7%)

(%)

20.8

Maximum Diode Current per Dxx

Output⁽⁴⁾

R_SET= 8.33kΩ

I_Dxx

DxA

Output Current Regulation

3.2V ≤ V_IN≤ 5.5V

V_LED= 3.6V

DxB

BankA, BankB, and BankC Enabled

(4)

DxC

BankA

3.0V ≤ V_IN≤ 5.5V

0.3

2.75

1.7

1.4

I_Dxx-MATCHLED Current Matching⁽⁵⁾

BankB

Gain = 3/2

Gain = 1

Open-Loop Charge Pump Output

R_OUT

Ω

Resistance

V_Dxx1x to 3/2x Gain Transition

Threshold

V_DxAand/or V_DxBFalling

R_SET= 16.9kΩ

V_DxTH

175

Current sink Headroom Voltage

I_Dxx= 95% ×I_Dxx(nom.)

(I_Dxx(nom) ≈ 15mA)

R_SET= 16.9kΩ

V_HR

Requirement

110

(6)

I_Q

Quiescent Supply Current

Shutdown Supply Current

I_SETPin Voltage

Gain = 1.5x, No Load

All ENx bits = "0"

2.7V ≤ V_IN≤ 5.5V

2.90

3.4

3.32

5.4

µA

I_SD

V_SET

I_{DxA-B-C /}

I_SET

1.25

Output Current to Current Set Ratio

BankA, BankB, BankC

200

f_SW

Switching Frequency

Start-up Time

0.89

1.27

250

1.57

MHz

µs

t_START

P_OUT= 90% steady state

Internal Diode Current PWM

Frequency

f_PWM

kHz

Reset

0.45

V_IN

V_RESET

Reset Voltage Thresholds

2.7V ≤ V_IN≤ 5.5V

Normal

Operation

1.2

I²C Compatible Interface Voltage Specifications (SCL, SDIO, VIO)

(7)

V_IO

Serial Bus Voltage Level

2.7V ≤ V_IN≤ 5.5V

1.4

V_IN

0.3 ×

V_IO

V_IL

Input Logic Low "0"

2.7V ≤ V_IN≤ 5.5V, VIO= 3.0V

0.7 ×

V_IO

V_IH

Input Logic High "1"

Output Logic Low "0"

2.7V ≤ V_IN≤ 5.5V, VIO= 3.0V

V_IO

V_OL

I_LOAD= 3mA

400

(4) The maximum total output current for the LM27965 should be limited to 180mA. The total output current can be split among any of the

three banks (I_DxA= I_DxB= I_DxC= 30mA Max.). Under maximum output current conditions, special attention must be given to input voltage

and LED forward voltage to ensure proper current regulation. See the Maximum Output Current section of the datasheet for more

information.

(5) For the two groups of current sinks on a part (BankA and BankB), the following are determined: the maximum sink current in the group

(MAX), the minimum sink current in the group (MIN), and the average sink current of the group (AVG). For each group, two matching

numbers are calculated: (MAX-AVG)/AVG and (AVG-MIN)/AVG. The largest number of the two (worst case) is considered the matching

figure for the bank. The matching figure for a given part is considered to be the highest matching figure of the two banks. The typical

specification provided is the most likely norm of the matching figure for all parts.

(6) For each Dxxpin, headroom voltage is the voltage across the internal current sink connected to that pin. For Group A, B, and C current

sinks, V_HRx= V_OUT-V_LED. If headroom voltage requirement is not met, LED current regulation will be compromised.

(7) SCL and SDIO signals are referenced to VIO and GND for minimum VIO voltage testing.

Submit Documentation Feedback

Product Folder Links: LM27965

LM27965

www.ti.com

SNVS380B –MAY 2006–REVISED FEBRUARY 2013

Electrical Characteristics^{(1) (2)}(continued)

Limits in standard typeface are for T_J= 25°C, and limits in boldface type apply over the full operating temperature range.

Unless otherwise specified: V_IN= 3.6V; V_RESET= V_IN; VIO = 1.8V V_DxA= V_DxB= V_DxC= 0.4V; R_SET= 12.7kΩ; BankA = BankB =

BankC = Fullscale Current; ENA, ENB, ENC, EN5A, EN3B Bits = “1”; C1 = C2 = C_IN= C_OUT= 1.0µF; Specifications related to

output current(s) and current setting pins (I_Dxxand I_SET) apply to BankA and BankB. ⁽³⁾

Symbol

Parameter

Condition

Min

Typ

Max

Units

I²C Compatible Interface Timing Specifications (SCL, SDIO, VIO)⁽⁸⁾

t₁

t₂

t₃

SCL (Clock Period)

2.5

100

µs

Data In Setup Time to SCL High

Data Out stable After SCL Low

SDIO Low Setup Time to SCL Low

(Start)

t₄

t₅

100

SDIO High Hold Time After SCL High

(Stop)

(8) SCL and SDIO should be glitch-free in order for proper brightness control to be realized.

Submit Documentation Feedback

Product Folder Links: LM27965

LM27965

SNVS380B –MAY 2006–REVISED FEBRUARY 2013

www.ti.com

BLOCK DIAGRAM

OUT

1 mF

C1+

C1-

C2+

C2-

D1A D2A D3A D4A D5A

D1B D2B D3B

D1C

OUT

3/2X and 1X

2.7V to 5.5V

Regulated Charge Pump

BankB

Current Sinks

D1C Current

Sink

1 mF

BankA Current Sinks

GAIN

CONTROL

LED

SENSE

LED

SENSE

Soft-

Start

1.25V

Ref.

Brightness

Control

Brightness

Control

Brightness

Control

1.27 MHz.

Switch

Frequency

20kHz PWM

Current Clock

RESET

General Purpose Register

SCL

SDIO

VIO

Brightness Control Registers

Bank A and Bank B

I C Interface

Block

Brightness Control Register

D1C

LM27965

SET

GND

SET

Submit Documentation Feedback

Product Folder Links: LM27965

LM27965

www.ti.com

SNVS380B –MAY 2006–REVISED FEBRUARY 2013

Typical Performance Characteristics

Unless otherwise specified: T_A= 25°C; V_IN= 3.6V; V_RESET= V_IN; V_LEDxA= V_LEDxB= V_LED1C= 3.6V; R_SET= 16.9kΩ; C₁=C₂= C_IN

= C_POUT= 1µF; ENA = ENB = ENC =EN5A = EN3B = '1'.

LED Drive Efficiency

Input Current

Input Voltage

Figure 1.

Figure 2.

BankA Current Regulation

BankB Current Regulation

Input Voltage

Figure 3.

Figure 4.

BankC Current Regulation

BankA Current Matching

Input Voltage

Figure 5.

Figure 6.

Submit Documentation Feedback

Product Folder Links: LM27965

LM27965

SNVS380B –MAY 2006–REVISED FEBRUARY 2013

www.ti.com

Typical Performance Characteristics (continued)

Unless otherwise specified: T_A= 25°C; V_IN= 3.6V; V_RESET= V_IN; V_LEDxA= V_LEDxB= V_LED1C= 3.6V; R_SET= 16.9kΩ; C₁=C₂= C_IN

= C_POUT= 1µF; ENA = ENB = ENC =EN5A = EN3B = '1'.

BankB Current Matching

BankA Diode Current

Brightness Register Code

Input Voltage

Figure 7.

Figure 8.

BankB Diode Current

Brightness Register Code

Figure 9.

Submit Documentation Feedback

Product Folder Links: LM27965

LM27965

www.ti.com

SNVS380B –MAY 2006–REVISED FEBRUARY 2013

CIRCUIT DESCRIPTION

OVERVIEW

The LM27965 is a white LED driver system based upon an adaptive 3/2× - 1× CMOS charge pump capable of

supplying up to 180mA of total output current. With three separately controlled banks of constant current sinks,

the LM27965 is an ideal solution for platforms requiring a single white LED driver for main display, sub display,

and indicator lighting. The tightly matched current sinks ensure uniform brightness from the LEDs across the

entire small-format display.

Each LED is configured in a common anode configuration, with the peak drive current being programmed

through the use of an external R_SETresistor. An I²C compatible interface is used to enable the device and vary

the brightness within the individual current sink banks. For BankA and BankB, 32 levels of brightness control are

available. The brightness control is achieved through a mix of analog and pulse width modulated (PWM)

methods. BankC has 4 analog brightness levels available.

CIRCUIT COMPONENTS

Charge Pump

The input to the 3/2× - 1x charge pump is connected to the V_INpin, and the regulated output of the charge pump

is connected to the V_OUTpin. The recommended input voltage range of the LM27965 is 3.0V to 5.5V. The

device’s regulated charge pump has both open loop and closed loop modes of operation. When the device is in

open loop, the voltage at V_OUTis equal to the gain times the voltage at the input. When the device is in closed

loop, the voltage at V_OUTis regulated to 4.6V (typ.). The charge pump gain transitions are actively selected to

maintain regulation based on LED forward voltage and load requirements.

LED Forward Voltage Monitoring

The LM27965 has the ability to switch converter gains (1x or 3/2x) based on the forward voltage of the LED load.

This ability to switch gains maximizes efficiency for a given load. Forward voltage monitoring occurs on all diode

pins within BankA and BankB. At higher input voltages, the LM27965 will operate in pass mode, allowing the

P_OUTvoltage to track the input voltage. As the input voltage drops, the voltage on the DXX pins will also drop

(V_DXX= V_POUT– V_LEDx). Once any of the active Dxx pins reaches a voltage approximately equal to 175mV, the

charge pump will switch to the gain of 3/2. This switch-over ensures that the current through the LEDs never

becomes pinched off due to a lack of headroom across the current sinks.

Only active Dxx pins will be monitored. For example, if only BankA is enabled, the LEDs in BankB will not affect

the gain transition point. If both banks are enabled, all diodes will be monitored, and the gain transition will be

based upon the diode with the highest forward voltage. Diode pins D5A and D3B can have the diode sensing

circuity disabled through the general purpose register if those drivers are not going to be used.

BankC (D1C) is not a monitored LED current sink.

RESETPin

The LM27965 has a hardware reset pin (RESET) that allows the device to be disabled by an external controller

without requiring an I²C write command. Under normal operation, the RESET pin should be held high (logic '1') to

prevent an unwanted reset. When the RESET is driven low (logic '0'), all internal control registers reset to the

default states and the part becomes disabled. Please see the Electrical Characteristics section of the datasheet

for required voltage thresholds.

I²C Compatible Interface

DATA VALIDITY

The data on SDIO line must be stable during the HIGH period of the clock signal (SCL). In other words, state of

the data line can only be changed when CLK is LOW.

Submit Documentation Feedback

Product Folder Links: LM27965

LM27965

SNVS380B –MAY 2006–REVISED FEBRUARY 2013

www.ti.com

SCL

SDIO

data

change

allowed

data

change

allowed

data

valid

data

change

allowed

data

valid

Figure 10. Data Validity Diagram

A pull-up resistor between VIO and SDIO must be greater than [(VIO-V_OL) / 3mA] to meet the V_OLrequirement

on SDIO. Using a larger pull-up resistor results in lower switching current with slower edges, while using a

smaller pull-up results in higher switching currents with faster edges.

START AND STOP CONDITIONS

START and STOP conditions classify the beginning and the end of the I²C session. A START condition is

defined as SDIO signal transitioning from HIGH to LOW while SCL line is HIGH. A STOP condition is defined as

the SDIO transitioning from LOW to HIGH while SCL is HIGH. The I²C master always generates START and

STOP conditions. The I²C bus is considered to be busy after a START condition and free after a STOP condition.

During data transmission, the I²C master can generate repeated START conditions. First START and repeated

START conditions are equivalent, function-wise.

SDIO

SCL

STOP condition

TART condition

Figure 11. Start and Stop Conditions

TRANSFERING DATA

Every byte put on the SDIO line must be eight bits long, with the most significant bit (MSB) transferred first. Each

byte of data has to be followed by an acknowledge bit. The acknowledge related clock pulse is generated by the

master. The master releases the SDIO line (HIGH) during the acknowledge clock pulse. The LM27965 pulls

down the SDIO line during the 9th clock pulse, signifying an acknowledge. The LM27965 generates an

acknowledge after each byte is received.

After the START condition, the I²C master sends a chip address. This address is seven bits long followed by an

eighth bit which is a data direction bit (R/W). The LM27965 address is 36h (38h for -M version). For the eighth

bit, a “0” indicates a WRITE and a “1” indicates a READ. The second byte selects the register to which the data

will be written. The third byte contains data to write to the selected register.

Submit Documentation Feedback

Product Folder Links: LM27965

LM27965

www.ti.com

SNVS380B –MAY 2006–REVISED FEBRUARY 2013

ack from slave

ack

ack from slave

start

msb Chip Address lsb

ack

msb Register Add lsb

msb DATA lsb

ack stop

SCL

SDIO

start

Id = 36h

ack

addr = 10h

ack

address h‘06 data

ack stop

Figure 12. Write Cycle

w = write (SDIO = "0")

r = read (SDIO = "1")

ack = acknowledge (SDIO pulled down by either master or slave)

id = chip address, 36h for LM27965 or 38h for LM27965-M

I²C COMPATIBLE CHIP ADDRESS

The chip address for LM27965 is 0110110, or 36h. The chip address for LM27965-M is 0111000, or 38h.

MSB

LSB

ADR6

bit7

ADR5

bit6

ADR4

bit5

ADR3

bit4

ADR2

bit3

ADR1

bit2

ADR0

bit1

R/W

bit0

LM27965

LM27965-M

I C Slave Address (chip address)

Figure 13. Chip Address

INTERNAL REGISTERS OF LM27965

Internal Hex Address

Power On Value

General Purpose Register

10h

0010 0000

1110 0000

1111 1100

Bank A Brightness Control Register

Bank B Brightness Control Register

Bank C Brightness Control Register

A0h

B0h

C0h

MSB

LSB

bit7

bit6

bit5

EN3B

bit4

EN5A

bit3

ENC

bit2

ENB

bit1

ENA

bit0

Figure 14. General Purpose Register Description

Internal Hex Address: 10h

NOTE

ENA: Enables DxA LED drivers (Main Display)

ENB: Enables DxB LED drivers (Aux Lighting)

ENC: Enables D1C LED driver (Indicator Lighting)

EN5A: Enables D5A LED voltage sense

EN3B: Enables D3B LED driver and voltage sense

Submit Documentation Feedback

Product Folder Links: LM27965

LM27965

SNVS380B –MAY 2006–REVISED FEBRUARY 2013

www.ti.com

DxA Brightness Control

MSB

LSB

bit7

bit6

bit5

DxA4

bit4

DxA3

bit3

DxA2

bit2

DxA1

bit1

DxA0

bit0

DxB Brightness Control

MSB

LSB

bit7

bit6

bit5

DxB4

bit4

DxB3

bit3

DxB2

bit2

DxB1

bit1

DxB0

bit0

DxC Brightness Control

MSB

LSB

bit7

bit6

bit5

bit4

bit3

bit2

D1C1

bit1

D1C0

bit0

Figure 15. Brightness Control Register Description

Internal Hex Address: 0xA0 (BankA), 0xB0 (BankB), 0xC0 (BankC)

NOTE

DxA4-DxA0: Sets Brightness for DxA pins (BankA). 11111=Fullscale

DxB4-DxB0: Sets Brightness for DxB pins (BankB). 11111=Fullscale

Bit7 to Bit 5: Not Used

DxC1-DxC0: Sets Brightness for DxC pin. 11 = Fullscale

Bit7 to Bit2:Not Used

Full-Scale Current set externally by the following equation:

I_Dxx= 200 × 1.25V / R_SET

Table 1. Brightness Level Control Table (BankA and BankB)

Analog Current (% of Full-

Brightness Code (hex)

Duty Cycle (%)

Perceived Brightness Level (%)

Scale)

1/16

2/16

1.25

2.5

3/16

3.75

4/16

5/16

6.25

7.5

6/16

7/16

8.75

8/16

9/16

11.25

12.5

13.75

10/16

11/16

12/16

13/16

14/16

15/16

16/16

10/16

11/16

12/16

16.25

17.5

18.75

27.5

Submit Documentation Feedback

Product Folder Links: LM27965

LM27965

www.ti.com

SNVS380B –MAY 2006–REVISED FEBRUARY 2013

Table 1. Brightness Level Control Table (BankA and BankB) (continued)

Analog Current (% of Full-

Scale)

Brightness Code (hex)

Duty Cycle (%)

Perceived Brightness Level (%)

13/16

14/16

15/16

16/16

11/16

12/16

13/16

14/16

15/16

16/16

13/16

15/16

16/16

32.5

37.5

48.125

52.5

56.875

61.25

65.625

100

81.25

93.75

100

BankC Brightness Levels (%of Full-Scale) = 20%, 40%, 70%, 100%

Submit Documentation Feedback

Product Folder Links: LM27965

LM27965

SNVS380B –MAY 2006–REVISED FEBRUARY 2013

www.ti.com

APPLICATION INFORMATION

SETTING LED CURRENT

The current through the LEDs connected to DxA and DxB can be set to a desired level simply by connecting an

appropriately sized resistor (R_SET) between the I_SETpin of the LM27965 and GND. The DxA and DxB LED

currents are proportional to the current that flows out of the I_SETpin and are a factor of 200 times greater than the

I_SETcurrent. The feedback loops of the internal amplifiers set the voltage of the I_SETpin to 1.25V (typ.). The

statements above are simplified in the equations below:

I_DxA/B/C(A)= 200 × (V_ISET/ R_SET

)

(1)

(2)

R_SET(Ω)= 200 × (1.25V / I_DxA/B/C

)

Once the desired R_SETvalue has been chosen, the LM27965 has the ability to internally dim the LEDs using a

mix of Pulse Width Modulation (PWM) and analog current scaling. The PWM duty cycle is set through the I²C

compatible interface. LEDs connected to BankA and BankB current sinks (DxA and DxB) can be dimmed to 32

different levels/duty-cycles. The internal PWM frequency for BankA and BankB is fixed at 20kHz. BankC(D1C)

has 4 analog current levels.

Please refer to the I²C Compatible Interface section of this datasheet for detailed instructions on how to adjust

the brightness control registers.

MAXIMUM OUTPUT CURRENT, MAXIMUM LED VOLTAGE, MINIMUM INPUT VOLTAGE

The LM27965 can drive 8 LEDs at 22.5mA each (BankA and BankB) from an input voltage as low as 3.2V, so

long as the LEDs have a forward voltage of 3.6V or less (room temperature).

The statement above is a simple example of the LED drive capabilities of the LM27965. The statement contains

the key application parameters that are required to validate an LED-drive design using the LM27965: LED

current (I_LEDx), number of active LEDs (N_x), LED forward voltage (V_LED), and minimum input voltage (V_IN-MIN).

The equation below can be used to estimate the maximum output current capability of the LM27965:

I_{LED_MAX}= [(1.5 x V_IN) - V_LED- (I_ADDITIONAL× R_OUT)] / [(N_xx R_OUT) + k_HRx

]

(3)

(4)

I_{LED_MAX}= [(1.5 x V_IN) - V_LED- (I_ADDITIONAL× 2.75Ω)] / [(N_xx 2.75Ω) + k_HRx

]

I_ADDITIONALis the additional current that could be delivered to the other LED banks.

R_OUT– Output resistance. This parameter models the internal losses of the charge pump that result in voltage

droop at the pump output P_OUT. Since the magnitude of the voltage droop is proportional to the total output

current of the charge pump, the loss parameter is modeled as a resistance. The output resistance of the

LM27965 is typically 2.75Ω (V_IN= 3.6V, T_A= 25°C). In equation form:

V_POUT= (1.5 × V_IN) – [(N_A× I_LEDA+ N_B× I_LEDB) × R_OUT

]

(5)

k_HR– Headroom constant. This parameter models the minimum voltage required to be present across the current

sinks for them to regulate properly. This minimum voltage is proportional to the programmed LED current, so the

constant has units of mV/mA. The typical k_HRof the LM27965 is 8mV/mA. In equation form:

(V_POUT– V_LEDx) > k_HRx× I_LEDx

(6)

Typical Headroom Constant Values

k_HRA= 8mV/mA

(7)

(8)

k_HRB= 8mV/mA

Equation 3 is obtained from combining the R_OUTEquation 5 with the k_HRxEquation 6 and solving for I_LEDx

Maximum LED current is highly dependent on minimum input voltage and LED forward voltage. Output current

capability can be increased by raising the minimum input voltage of the application, or by selecting an LED with a

lower forward voltage. Excessive power dissipation may also limit output current capability of an application.

Submit Documentation Feedback

Product Folder Links: LM27965

LM27965

www.ti.com

SNVS380B –MAY 2006–REVISED FEBRUARY 2013

Total Output Current Capability

The maximum output current that can be drawn from the LM27965 is 180mA. Each driver bank has a maximum

allotted current per Dxx sink that must not be exceeded.

DRIVER TYPE

MAXIMUM Dxx CURRENT

30mA per DxA Pin

DxA

DxB

DxC

30mA per DxB Pin

The 180mA load can be distributed in many different configurations. Special care must be taken when running

the LM27965 at the maximum output current to ensure proper functionality.

PARALLEL CONNECTED AND UNUSED OUTPUTS

Outputs D1A-5A or D1B-D3B may be connected together to drive one or two LEDs at higher currents. In such a

configuration, all five parallel current sinks (BankA) of equal value can drive a single LED. The LED current

programmed for BankA should be chosen so that the current through each of the outputs is programmed to 20%

of the total desired LED current. For example, if 60mA is the desired drive current for a single LED, R_SETshould

be selected such that the current through each of the current sink inputs is 12mA.

Connecting the outputs in parallel does not affect internal operation of the LM27965 and has no impact on the

Electrical Characteristics and limits previously presented. The available diode output current, maximum diode

voltage, and all other specifications provided in the Electrical Characteristics table apply to this parallel output

configuration, just as they do to the standard 5-LED application circuit.

Both BankA and BankB utilize LED forward voltage sensing circuitry on each Dxx pin to optimize the charge-

pump gain for maximum efficiency. Due to the nature of the sensing circuitry, it is not recommended to leave any

of the DxA (D1A-D4A) or DxB (D1B-D2B) pins open if either diode bank is going to be used during normal

operation. Leaving DxA and/or DxB pins unconnected will force the charge-pump into 3/2× mode over the entire

V_INrange negating any efficiency gain that could have been achieved by switching to 1× mode at higher input

voltages.

If D5A is not used, it is recommended that the driver pin be grounded and the general purpose register bit EN5A

be set to 0 to ensure proper gain transitions.

The D3B driver can be completely turned on or off on the fly using the general purpose register. The diode

monitoring circuity is enabled and disabled with the driver. If D3B is not used, it is recommended that the driver

pin be grounded and the general purpose register bit EN3B be set to 0 to ensure proper gain transitions.

Care must be taken when selecting the proper R_SETvalue. The current on any Dxx pin must not exceed the

maximum current rating for any given current sink pin.

POWER EFFICIENCY

Efficiency of LED drivers is commonly taken to be the ratio of power consumed by the LEDs (P_LED) to the power

drawn at the input of the part (P_IN). With a 3/2× - 1× charge pump, the input current is equal to the charge pump

gain times the output current (total LED current). The efficiency of the LM27965 can be predicted as follows:

P_LEDTOTAL= (V_LEDA× N_A× I_LEDA) + (V_LEDB× N_B× I_LEDB) + (V_LEDC× I_LEDC

)

(9)

(10)

(11)

(12)

P_IN= V_IN× I_IN

P_IN= V_IN× (GAIN × I_LEDTOTAL+ I_Q)

E = (P_LEDTOTAL÷ P_IN)

The LED voltage is the main contributor to the charge-pump gain selection process. Use of low forward-voltage

LEDs (3.0V- to 3.5V) will allow the LM27965 to stay in the gain of 1× for a higher percentage of the lithium-ion

battery voltage range when compared to the use of higher forward voltage LEDs (3.5V to 4.0V). See the LED

Forward Voltage Monitoring section of this datasheet for a more detailed description of the gain selection and

transition process.

For an advanced analysis, it is recommended that power consumed by the circuit (V_INx I_IN) for a given load be

evaluated rather than power efficiency.

Submit Documentation Feedback

Product Folder Links: LM27965

LM27965

SNVS380B –MAY 2006–REVISED FEBRUARY 2013

www.ti.com

POWER DISSIPATION

The power dissipation (P_DISS) and junction temperature (T_J) can be approximated with the equations below. P_INis

the power generated by the 3/2× - 1× charge pump, P_LEDis the power consumed by the LEDs, T_Ais the ambient

temperature, and θ_JAis the junction-to-ambient thermal resistance for the WQFN-24 package. V_INis the input

voltage to the LM27965, V_LEDis the nominal LED forward voltage, N is the number of LEDs and I_LEDis the

programmed LED current.

P_DISS= P_IN- P_LEDA- P_LEDB- P_LEDC

(13)

(14)

(15)

P_DISS= (GAIN × V_IN× I_{BANKA + BANKB + BANKC}) - (V_LEDA× N_A× I_LEDA) - (V_LEDB× N_B× I_LEDB) - (V_LEDC× I_LEDC

)

T_J= T_A+ (P_DISSx θ_JA)

The junction temperature rating takes precedence over the ambient temperature rating. The LM27965 may be

operated outside the ambient temperature rating, so long as the junction temperature of the device does not

exceed the maximum operating rating of 100°C. The maximum ambient temperature rating must be derated in

applications where high power dissipation and/or poor thermal resistance causes the junction temperature to

exceed 100°C.

THERMAL PROTECTION

Internal thermal protection circuitry disables the LM27965 when the junction temperature exceeds 170°C (typ.).

This feature protects the device from being damaged by high die temperatures that might otherwise result from

excessive power dissipation. The device will recover and operate normally when the junction temperature falls

below 165°C (typ.). It is important that the board layout provide good thermal conduction to keep the junction

temperature within the specified operating ratings.

CAPACITOR SELECTION

The LM27965 requires 4 external capacitors for proper operation (C₁= C₂= C_IN= C_OUT= 1µF). Surface-mount

multi-layer ceramic capacitors are recommended. These capacitors are small, inexpensive and have very low

equivalent series resistance (ESR <20mΩ typ.). Tantalum capacitors, OS-CON capacitors, and aluminum

electrolytic capacitors are not recommended for use with the LM27965 due to their high ESR, as compared to

ceramic capacitors.

For most applications, ceramic capacitors with X7R or X5R temperature characteristic are preferred for use with

the LM27965. These capacitors have tight capacitance tolerance (as good as ±10%) and hold their value over

temperature (X7R: ±15% over -55°C to 125°C; X5R: ±15% over -55°C to 85°C).

Capacitors with Y5V or Z5U temperature characteristic are generally not recommended for use with the

LM27965. Capacitors with these temperature characteristics typically have wide capacitance tolerance (+80%, -

20%) and vary significantly over temperature (Y5V: +22%, -82% over -30°C to +85°C range; Z5U: +22%, -56%

over +10°C to +85°C range). Under some conditions, a nominal 1µF Y5V or Z5U capacitor could have a

capacitance of only 0.1µF. Such detrimental deviation is likely to cause Y5V and Z5U capacitors to fail to meet

the minimum capacitance requirements of the LM27965.

The minimum voltage rating acceptable for all capacitors is 6.3V. The recommended voltage rating for

the capacitors is 10V to account for DC bias capacitance losses.

PCB LAYOUT CONSIDERATIONS

The WQFN is a leadframe based Chip Scale Package (CSP) with very good thermal properties. This package

has an exposed DAP (die attach pad) at the center of the package measuring 2.6mm x 2.5mm. The main

advantage of this exposed DAP is to offer lower thermal resistance when it is soldered to the thermal land on the

PCB. For PCB layout, National highly recommends a 1:1 ratio between the package and the PCB thermal land.

To further enhance thermal conductivity, the PCB thermal land may include vias to a ground plane. For more

detailed instructions on mounting WQFN packages, please refer to Application Note AN-1187 (SNOA401).

Submit Documentation Feedback

Product Folder Links: LM27965

LM27965

www.ti.com

SNVS380B –MAY 2006–REVISED FEBRUARY 2013

REVISION HISTORY

Changes from Revision A (February 2013) to Revision B

Page

•

Changed layout of National Data Sheet to TI format .......................................................................................................... 16

Submit Documentation Feedback

Product Folder Links: LM27965

PACKAGE OPTION ADDENDUM

www.ti.com

10-Dec-2020

PACKAGING INFORMATION

Orderable Device

Status Package Type Package Pins Package

Eco Plan

Lead finish/

Ball material

MSL Peak Temp

Op Temp (°C)

Device Marking

Samples

Drawing

Qty

(1)

(2)

(3)

(4/5)

(6)

LM27965SQ-M/NOPB

LM27965SQ/NOPB

LM27965SQX/NOPB

ACTIVE

WQFN

RTW

1000 RoHS & Green

4500 RoHS & Green

Level-1-260C-UNLIM

27965M

-30 to 85

L27965S

⁽¹⁾The marketing status values are defined as follows:

ACTIVE: Product device recommended for new designs.

LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.

NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.

PREVIEW: Device has been announced but is not in production. Samples may or may not be available.

OBSOLETE: TI has discontinued the production of the device.

⁽²⁾RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance

do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may

reference these types of products as "Pb-Free".

RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.

Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based

flame retardants must also meet the <=1000ppm threshold requirement.

⁽³⁾MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.

⁽⁴⁾There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.

⁽⁵⁾Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation

of the previous line and the two combined represent the entire Device Marking for that device.

(6)

Lead finish/Ball material - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead finish/Ball material values may wrap to two

lines if the finish value exceeds the maximum column width.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information

provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and

continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.

TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.

Addendum-Page 1

PACKAGE OPTION ADDENDUM

www.ti.com

10-Dec-2020

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.

Addendum-Page 2

PACKAGE MATERIALS INFORMATION

www.ti.com

2-Sep-2015

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device

Package Package Pins

Type Drawing

SPQ

Reel

Pin1

Diameter Width (mm) (mm) (mm) (mm) (mm) Quadrant

(mm) W1 (mm)

LM27965SQ-M/NOPB

LM27965SQ/NOPB

LM27965SQX/NOPB

WQFN

RTW

1000

4500

178.0

330.0

12.4

4.3

1.3

8.0

12.0

Pack Materials-Page 1

PACKAGE MATERIALS INFORMATION

www.ti.com

2-Sep-2015

*All dimensions are nominal

Device

Package Type Package Drawing Pins

SPQ

Length (mm) Width (mm) Height (mm)

LM27965SQ-M/NOPB

LM27965SQ/NOPB

LM27965SQX/NOPB

WQFN

RTW

1000

4500

210.0

367.0

185.0

367.0

35.0

Pack Materials-Page 2

PACKAGE OUTLINE

RTW0024A

WQFN - 0.8 mm max height

PLASTIC QUAD FLATPACK - NO LEAD

4.1

3.9

PIN 1 INDEX AREA

4.1

3.9

0.8 MAX

SEATING PLANE

0.08 C

0.05

0.00

2X 2.5

(0.1) TYP

EXPOSED

THERMAL PAD

20X 0.5

2.5

2.6 0.1

0.3

24X

0.2

PIN 1 ID

(OPTIONAL)

0.1

C A B

0.05

0.5

0.3

24X

4222815/A 03/2016

NOTES:

1. All linear dimensions are in millimeters. Any dimensions in parenthesis are for reference only. Dimensioning and tolerancing

per ASME Y14.5M.

2. This drawing is subject to change without notice.

3. The package thermal pad must be soldered to the printed circuit board for thermal and mechanical performance.

www.ti.com

EXAMPLE BOARD LAYOUT

RTW0024A

WQFN - 0.8 mm max height

PLASTIC QUAD FLATPACK - NO LEAD

(

2.6)

SYMM

24X (0.6)

24X (0.25)

(1.05)

SYMM

(3.8)

20X (0.5)

(R0.05)

TYP

(

0.2) TYP

VIA

(1.05)

(3.8)

LAND PATTERN EXAMPLE

SCALE:15X

0.07 MIN

ALL AROUND

0.07 MAX

ALL AROUND

SOLDER MASK

OPENING

METAL

SOLDER MASK

OPENING

METAL UNDER

SOLDER MASK

NON SOLDER MASK

DEFINED

SOLDER MASK

DEFINED

(PREFERRED)

SOLDER MASK DETAILS

4222815/A 03/2016

NOTES: (continued)

4. This package is designed to be soldered to a thermal pad on the board. For more information, see Texas Instruments literature

number SLUA271 (www.ti.com/lit/slua271).

www.ti.com

EXAMPLE STENCIL DESIGN

RTW0024A

WQFN - 0.8 mm max height

PLASTIC QUAD FLATPACK - NO LEAD

4X ( 1.15)

(0.675) TYP

(R0.05) TYP

24X (0.6)

24X (0.25)

(0.675)

TYP

SYMM

20X (0.5)

(3.8)

METAL

TYP

SYMM

(3.8)

SOLDER PASTE EXAMPLE

BASED ON 0.125 mm THICK STENCIL

EXPOSED PAD 25:

78% PRINTED SOLDER COVERAGE BY AREA UNDER PACKAGE

SCALE:20X

4222815/A 03/2016

NOTES: (continued)

5. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate

design recommendations.

www.ti.com

IMPORTANT NOTICE AND DISCLAIMER

TI PROVIDES TECHNICAL AND RELIABILITY DATA (INCLUDING DATA SHEETS), DESIGN RESOURCES (INCLUDING REFERENCE

DESIGNS), APPLICATION OR OTHER DESIGN ADVICE, WEB TOOLS, SAFETY INFORMATION, AND OTHER RESOURCES “AS IS”

AND WITH ALL FAULTS, AND DISCLAIMS ALL WARRANTIES, EXPRESS AND IMPLIED, INCLUDING WITHOUT LIMITATION ANY

IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRD

PARTY INTELLECTUAL PROPERTY RIGHTS.

These resources are intended for skilled developers designing with TI products. You are solely responsible for (1) selecting the appropriate

TI products for your application, (2) designing, validating and testing your application, and (3) ensuring your application meets applicable

standards, and any other safety, security, regulatory or other requirements.

These resources are subject to change without notice. TI grants you permission to use these resources only for development of an

application that uses the TI products described in the resource. Other reproduction and display of these resources is prohibited. No license

is granted to any other TI intellectual property right or to any third party intellectual property right. TI disclaims responsibility for, and you

will fully indemnify TI and its representatives against, any claims, damages, costs, losses, and liabilities arising out of your use of these

resources.

TI’s products are provided subject to TI’s Terms of Sale or other applicable terms available either on ti.com or provided in conjunction with

such TI products. TI’s provision of these resources does not expand or otherwise alter TI’s applicable warranties or warranty disclaimers for

TI products.

TI objects to and rejects any additional or different terms you may have proposed. IMPORTANT NOTICE

Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265

LM27965SQ/NOPB [TI]

相关型号：

LM27965SQX

LM27965SQX-M

LM27965SQX/NOPB

LM27965_07

LM27966

LM27966

LM27966SQ

LM27966SQ/NOPB

LM27966SQX

LM2796TL

LM2796TL/NOPB

LM2796TLX