34713--Datasheet/数据表在线中文翻译

Document Number: MC34713

Rev. 4.0, 5/2007

Freescale Semiconductor

Advance Information

5.0 A 1.0 MHz Fully Integrated

Single Switch-Mode Power

Supply

34713

The 34713 is a highly integrated, space efficient, low cost, single

synchronous buck switching regulator with integrated N-channel

power MOSFETs. It is a high performance point-of-load (PoL) power

supply with the ability to track an external reference voltage in

different configurations.

SWITCH-MODE POWER SUPPLY

Its high efficient 5.0 A continuous output current capability

combined with its voltage tracking/sequencing ability and tight output

regulation, makes it ideal as a single power supply.

The 34713 offers the designer the flexibility of many control,

supervisory, and protection functions to allow for easy implementation

of complex designs. It is housed in a Pb-Free, thermally enhanced,

and space-efficient 24-Pin Exposed Pad QFN.

Features

• 45 mΩ Integrated N-Channel Power MOSFETs

• Input Voltage Operating Range from 3.0 V to 6.0 V

EP SUFFIX

98ARL10577D

24-PIN QFN

•

±1 % Accurate Output Voltage, Ranging from 0.7 V to 3.6 V

• Voltage Tracking Capability in different configurations.

• Programmable Switching Frequency Range from 200 kHz to

1.0 MHz with a default of 1.0 MHz

• Programmable Soft Start Timing

• Over Current Limit and Short Circuit Protection

• Thermal Shutdown

• Output Overvoltage and Undervoltage Detection

• Active Low Power Good Output Signal

• Active Low Shutdown Input

ORDERING INFORMATION

Temperature

Package

Device

Range (T )

A

MC34713EP/R2

-40 to 85°C

24 QFN

• Pb-Free Packaging Designated by Suffix Code EP.

(3.0V TO 6.0V) VIN

34713

V_MASTER

VIN

PVIN

BOOT

SW

VREFIN

PGND

VDDI

V

OUT

INV

FREQ

ILIM

COMP

VOUT

VIN

MICROCONTROLLER

DSP,

FPGA,

ASIC

PG

SD

GND

Figure 1. 34713 Simplified Application Diagram

* This document contains certain information on a new product.

Specifications and information herein are subject to change without notice.

INTERNAL BLOCK DIAGRAM

SD

Internal

Voltage

Regulator

VIN

Thermal

Monitoring

PG

M2

System

Reset

System

Control

M1

V_DDI

BOOT

PVIN

I_LIMIT

Discharge

V_INV_BOOT

Buck

Control

Logic

Oscillator

F_SW

Prog Frequency

M3

M4

FREQ

ILIM

Gate

Driver

I_SENSE

SW

Prog Soft Start

I_SENSE

Current

Monitoring

I_LIMIT

PWM

Comparator

V_DDI

–

PGND

COMP

VDDI

Ramp

Generator

V_BG

Bandgap

Regulator

Error

Amplifier

–

INV

VREFIN

GND

Reference

Selection

V_BG

M5

VOUT

Discharge

Figure 2. 34713 Simplified Internal Block Diagram

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Analog Integrated Circuit Device Data

Freescale Semiconductor

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PIN CONNECTIONS

20 19

22 21

24

23

GND

FREQ

ILIM

1

PVIN

18

17

16

2

3

SW

Transparent

Top View

4

15 SW

PG

NC

14

13

PGND

5

6

SD

12

8

9

10

11

7

Figure 3. 34713 Pin Connections

Table 1. 34713 Pin Definitions

A functional description of each pin can be found in the Functional Pin Description section beginning on page 9.

Pin Number Pin Name Pin Function

Formal Name

Definition

Analog signal ground of IC

1

2

3

4

GND

FREQ

ILIM

Ground

Passive

Input

Signal Ground

Frequency Adjustment

Soft Start

Buck converter switching frequency adjustment pin

Soft Start adjustment

Active-low (open drain) power-good status reporting pin

PG

Output

Power Good

No internal connections to these pins. Recommend attaching a 0.1µF

capacitor from pin 8 to GND.

5, 8

6

None

Input

No Connect

Shutdown

NC

Shutdown mode input control pin

SD

VREFIN

COMP

INV

Voltage-Tracking-

Reference Input

Voltage-Tracking-Reference voltage input

7

Input

Buck converter external compensation network pin

Buck converter error amplifier inverting input pin

9

Passive

Input

Compensation

Error Amplifier

Inverting Input

10

Discharge FET drain connection (connect to buck converter output

capacitors)

Output Voltage

Discharge FET

11

VOUT

Output

Ground return for buck converter and discharge FET

Buck converter power switching node

12,13,14

15,16,17

PGND

SW

Ground

Power

Power Ground

Switching Node

Power-Circuit Supply Buck converter main supply voltage input

Input

18,19,20

21

PVIN

BOOT

VIN

Supply

Passive

Supply

Bootstrap switching node (connect to bootstrap capacitor)

Bootstrap

Logic-Circuit Supply

Input

Logic circuits supply voltage input

22,23

Internal Voltage

Regulator

Internal Vdd Regulator (connect filter capacitor to this pin)

24

VDDI

Passive

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ELECTRICAL CHARACTERISTICS

MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

MAXIMUM RATINGS

Table 2. Maximum Ratings

All voltages are with respect to ground unless otherwise noted. Exceeding these ratings may cause a malfunction or

permanent damage to the device.

Ratings

Symbol

Value

Unit

ELECTRICAL RATINGS

Input Supply Voltage (VIN) Pin

V_IN

-0.3 to 7.0

-0.3 to 7.5

-0.3 to 7.0

-0.3 to 3.0

+5.0

V

A

High-Side MOSFET Drain Voltage (PVIN) Pin

Switching Node (SW) Pin

PV_IN

V_SW

BOOT Pin (Referenced to SW Pin)

PG, VOUT,and SD Pins

V_BOOT- V_SW

-

VDDI, FREQ, ILIM, INV, COMP, and VREFIN Pins

Continuous Output Current ⁽¹⁾

ESD Voltage ⁽²⁾

I_OUT

V_ESD1

±2000

±750

V

Human Body Model

Charge Device Model

V

ESD3

THERMAL RATINGS

Operating Ambient Temperature ⁽³⁾

Storage Temperature

T_A

T_STG

T_PPRT

T_J(MAX)

P_D

-40 to 85

-65 to +150

Note 5

°C

Peak Package Reflow Temperature During Reflow ⁽⁴⁾

Maximum Junction Temperature

Power Dissipation (T_A= 85 °C) ⁽⁶⁾

Notes

,

(5)

+150

2.9

°C

W

1. Continuous output current capability so long as T is ≤ T_J(MAX)

.

J

2. ESD1 testing is performed in accordance with the Human Body Model (C

accordance with the Charge Device Model (CDM).

=100 pF, R

=1500 Ω), ESD3 testing is performed in

ZAP

3. The limiting factor is junction temperature, taking into account power dissipation, thermal resistance, and heatsinking.

4. Pin soldering temperature limit is for 10 seconds maximum duration. Not designed for immersion soldering. Exceeding these limits may

cause malfunction or permanent damage to the device.

5. Freescale’s Package Reflow capability meets Pb-free requirements for JEDEC standard J-STD-020C. For Peak Package Reflow

Temperature and Moisture Sensitivity Levels (MSL),

Go to www.freescale.com, search by part number [e.g. remove prefixes/suffixes and enter the core ID to view all orderable parts. (i.e.

MC33xxxD enter 33xxx), and review parametrics.

6. Maximum power dissipation at indicated ambient temperature

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ELECTRICAL CHARACTERISTICS

MAXIMUM RATINGS

Table 2. Maximum Ratings (continued)

All voltages are with respect to ground unless otherwise noted. Exceeding these ratings may cause a malfunction or

permanent damage to the device.

Ratings

Symbol

Value

Unit

THERMAL RESISTANCE ⁽⁷⁾

Thermal Resistance, Junction to Ambient, Single-Layer Board (1s) ⁽⁸⁾

Thermal Resistance, Junction to Ambient, Four-Layer Board (2s2p) ⁽⁹⁾

Thermal Resistance, Junction to Board ⁽¹⁰⁾

R_θJA

R_θJMA

R_θJB

139

43

°C/W

22

Notes

7. The PVIN, SW, and PGND pins comprise the main heat conduction paths.

8. Per SEMI G38-87 and JEDEC JESD51-2 with the single-layer board (JESD51-3) horizontal.

9. Per JEDEC JESD51-6 with the board (JESD51-7) horizontal. There are no thermal vias connecting the package to the two planes in the

board.

10. Thermal resistance between the device and the printed circuit board per JEDEC JESD51-8. Board temperature is measured on the top

surface of the board near the package.

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ELECTRICAL CHARACTERISTICS

STATIC ELECTRICAL CHARACTERISTICS

Table 3. Static Electrical Characteristics

Characteristics noted under conditions 3.0 V ≤ V_IN≤ 6.0 V, -40°C ≤ T_A≤ 85°C, GND = 0 V unless otherwise noted. Typical

values noted reflect the approximate parameter means at T_A= 25°C under nominal conditions unless otherwise noted.

Characteristic

IC INPUT SUPPLY VOLTAGE (VIN)

Symbol

Min

Typ

Max

Unit

Input Supply Voltage Operating Range

V_IN

I_IN

3.0

-

6.0

25

V

Input DC Supply Current ⁽¹¹⁾

mA

Normal Mode: SD = 1, Unloaded Outputs

Input DC Supply Current ⁽¹¹⁾

Shutdown Mode, SD = 0

I_INOFF

-

100

µA

V

INTERNAL SUPPLY VOLTAGE OUTPUT (VDDI)

Internal Supply Voltage Range

V_DDI

2.35

2.5

2.65

BUCK CONVERTER (PVIN, SW, PGND, BOOT, INV, COMP, ILIM)

Output Voltage Adjustment Range ^{(12), (13)}

Output Voltage Accuracy ^{(12), (14)}

V_OUT

-

0.7

-

3.6

1.0

V

-1.0

%

Line Regulation ⁽¹²⁾

REG_LN

REG_LD

-1.0

-

1.0

%

Normal Operation, V_IN= 3.0 V to 6.0 V, I_OUT= +5.0 A

Load Regulation ⁽¹²⁾

Normal Operation, I_OUT= 0.0 A to 5.0 A

Error Amplifier Common Mode Voltage Range ^{(12), (13)}

Output Undervoltage Threshold

Output Overvoltage Threshold

Continuous Output Current

V

0.0

-1.5

1.5

-

1.35

-8.0

8.0

5.0

-

V

%

A

REF

V_UVR

V_OVR

I_OUT

-

Over Current Limit

I_LIM

-

6.5

-

A

Soft start Adjusting reference Voltage Range

Short Circuit Current Limit

V_ILIM

I_SHORT

1.25

-

V_DDI

-

V

8.5

A

(12)

High-Side N-CH Power MOSFET (M3) R_DS(ON)

R_DS(ON)HS

10

-

45

mΩ

I_OUT= 1.0 A, V_BOOT- V_SW= 3.3 V

(12)

Low-Side N-CH Power MOSFET (M4) R_DS(ON)

R_DS(ON)LS

I_OUT= 1.0 A, V_IN= 3.3 V

Notes

11. Section “MODES OF OPERATION”, page 12 has a detailed description of the different operating modes of the 34713

12. Design information only, this parameter is not production tested.

13. The ±1% accuracy is only guaranteed for VEFOUT greater then or equal 0.7V at room tempreature.

14. Overall output accuracy is directly affected by the accuracy of the external feedback network, 1% feedback resistors are recommended

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ELECTRICAL CHARACTERISTICS

STATIC ELECTRICAL CHARACTERISTICS

Table 3. Static Electrical Characteristics

Characteristics noted under conditions 3.0 V ≤ V_IN≤ 6.0 V, -40°C ≤ T_A≤ 85°C, GND = 0 V unless otherwise noted. Typical

values noted reflect the approximate parameter means at T_A= 25°C under nominal conditions unless otherwise noted.

Characteristic

Symbol

Min

Typ

Max

Unit

M2 R_DS(ON)

R_DS(ON)M2

1.5

-

4.0

Ω

V_IN= 3.3 V, M2 is on

PVIN Pin Leakage Current

Shutdown Mode

I_PVIN

-10

-

10

µA

INV Pin Leakage Current

I_INV

-1.0

-

1.0

µA

°C

Thermal Shutdown Threshold ⁽¹⁵⁾

Thermal Shutdown Hysteresis ⁽¹⁵⁾

OSCILLATOR (FREQ)

T_SDFET

T_SDHYFET

-

170

25

-

Oscillator Frequency Adjusting Reference Voltage Range

V_FREQ

0.0

-

V_DDI

V

TRACKING (VREFIN, VOUT)

VREFIN External Reference Voltage Range ⁽¹⁵⁾

VOUT Total Discharge Resistance⁽¹⁵⁾

CONTROL AND SUPERVISORY (SD, PG)

SD High Level Input Voltage

V_REFIN

0.0

-

1.35

-

V

R_TDR(M5)

50

Ω

V_SDHI

V_SDLO

R_SDUP

2.0

-

V

SD Low Level Input Voltage

0.4

2.0

SD Pin Internal Pull Up Resistor ⁽¹⁵⁾

1.0

MΩ

PG Low Level Output Voltage

I_PG= 3.0 mA

V_PGLO

-

0.4

1.0

V

PG Pin Leakage Current

M1 is off, Pulled up to VIN

I_PGLKG

-1.0

µA

Notes

15. Design information only, this parameter is not production tested.

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Freescale Semiconductor

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ELECTRICAL CHARACTERISTICS

DYNAMIC ELECTRICAL CHARACTERISTICS

Table 4. Dynamic Electrical Characteristics

Characteristics noted under conditions 3.0 V ≤ V_IN≤ 6.0 V, -40°C ≤ T_A≤ 85°C, GND = 0 V unless otherwise noted. Typical

values noted reflect the approximate parameter means at T_A= 25°C under nominal conditions unless otherwise noted.

Characteristic

Symbol

Min

Typ

Max

Unit

BUCK CONVERTER (PVIN, SW, PGND, BOOT)

Switching Node (SW) Rise Time ⁽¹⁶⁾

(P_VIN= 3.3 V, I_OUT= 5.0 A)

t_RISE

-

14

20

-

ns

Switching Node (SW) Fall Time ⁽¹⁶⁾

(P_VIN= 3.3 V, I_OUT= 5.0 A)

t_FALL

Soft Start Duration (Normal Mode)

ILIM= 1.25 - 1.49 V

1.50 - 1.81 V

-

3.2

1.6

0.8

0.4

-

t

ms

SS

1.82 - 2.13 V

2.14 - 2.50 V

Over Current Limit Timer

t

-

10

-

ms

µs

LIM

Over Current Limit Retry Time-out Period

Output Undervoltage/Overvoltage Filter Delay Timer

OSCILLATOR (FREQ)

t

80

5.0

120

25

TIMEOUT

t

-

FILTER

Oscillator Default Switching Frequency

f

-

1.0

-

MHz

KHz

SW

Oscillator Frequency tolerance is ±10% (FREQ = GND)

Oscillator Switching Frequency Range

200

1000

CONTROL AND SUPERVISORY (SD, PG)

PG Reset Delay

t

8.0

80

-

12

ms

PGRESET

Thermal Shutdown Retry Time-out Period ⁽¹⁶⁾

t

120

TIMEOUT

Notes

16. Design information only, this parameter is not production tested.

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Analog Integrated Circuit Device Data

Freescale Semiconductor

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FUNCTIONAL DESCRIPTION

INTRODUCTION

FUNCTIONAL DESCRIPTION

INTRODUCTION

Advanced microprocessor-based systems require

compact, efficient, and accurate point-of-load (PoL) power

supplies. These PoL supply high current and fast transient

response capability while maintaining regulation accuracy.

Voltage monitoring (power sequencing) and increased

operating frequency are also key features for PoL power

supplies.

efficiency operation. It provides an output voltage with an

accuracy of less than ±2.0 %, capable of supplying up to

5.0 A of continuous current. Its power sequencing/tracking

abilities makes it ideal for systems with multiple related

supply rails. It has an adjustable switching frequency, thus

permitting greater design flexibility and optimization over a

wide range of operating conditions, and can operate at up to

1.0 MHz to significantly reduce the external components size

and cost. It also features an over-current limit control, and

protects against output overvoltage, undervoltage, and

overtemperature conditions. It also protects the system from

short circuit events and incorporates a power-good output

signal to alert the host MCU should a fault occur.

PoL power supplies are non-isolated DC to DC converters

that are physically located near their load (on the same

printed circuit board) and take their input supply from an

intermediate bus. Their close proximity to the load allows for

higher efficiency, localized protection, and minimum

distribution losses. Their compact design and low

component-count also reduces overall system cost.

Operation can be enabled or disabled by controlling the

SD pin, which offers power sequencing capabilities.

The 34713 is a PoL single-output power supply that

embodies an integrated solution that’s both highly cost-

effective and reliable. It utilizes a voltage-mode synchronous

buck switching converter topology with integrated low

R_DS(ON)(45 mΩ) N-channel power MOSFETs for high-

By monolithically integrating the control and supervisory

circuitry along with power-FETs, the 34713 offers a complete,

compact, cost-effective, and simple solution to satisfy the

PoL needs of today’s systems.

FUNCTIONAL PIN DESCRIPTION

REFERENCE VOLTAGE INPUT (VREFIN)

ERROR AMPLIFIER INVERTING INPUT (INV)

The 34713 will track the voltage applied at this pin.

Buck converter error amplifier inverting input. Connect the

output voltage feedback network to this pin.

FREQUENCY ADJUSTMENT INPUT (FREQ)

COMPENSATION INPUT (COMP)

The buck converter switching frequency can be adjusted

by connecting this pin to an external resistor divider between

VDDI and GND pins. The default switching frequency (FREQ

pin connected to ground, GND) is set at 1.0 MHz.

Buck converter external compensation network connects

to this pin. Use a type III compensation network.

INPUT SUPPLY VOLTAGE (VIN)

SOFT START ADJUSTMENT INPUT (ILIM)

IC power supply input voltage. Input filtering is required for

the device to operate properly.

Soft start timing can be adjusted by applying an external

voltage between 1.25 and V_DDIon this pin.

POWER GROUND (PGND)

SIGNAL GROUND (GND)

Buck converter and discharge MOSFET power ground. It

is the source of the buck converter low-side power MOSFET.

Analog ground of the IC. Internal analog signals are

referenced to this pin voltage.

SWITCHING NODE (SW)

INTERNAL SUPPLY VOLTAGE OUTPUT (VDDI)

Buck converter switching node. This pin is connected to

the output inductor.

This is the output of the internal bias voltage regulator.

Connect a 1.0 µF, 6 V low ESR ceramic filter capacitor

between this pin and the GND pin. Filtering any spikes on this

output is essential to the internal circuitry stable operation.

POWER INPUT VOLTAGE (PVIN)

Buck converter power input voltage. This is the drain of the

buck converter high-side power MOSFET.

OUTPUT VOLTAGE DISCHARGE PATH (VOUT)

Output voltage of the Buck Converter is connected to this

pin. it only serves as the output discharge path once the SD

signal is asserted.

BOOTSTRAP INPUT (BOOT)

Bootstrap capacitor input pin. Connect a capacitor (as

discussed on page 17) between this pin and the SW pin to

enhance the gate of the high-side Power MOSFET during

switching.

34713

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9

FUNCTIONAL DESCRIPTION

FUNCTIONAL INTERNAL BLOCK DESCRIPTION

SHUTDOWN INPUT (SD)

POWER GOOD OUTPUT SIGNAL (PG)

If this pin is tied to the GND pin, the device will be in

Shutdown Mode. If left unconnected or tied to the VIN pin, the

device will be in Normal Mode. The pin has an internal pull up

of 1.5 MΩ.

This is an active low open drain output that is used to

report the status of the device to a host. This output activates

after a successful power up sequence and stays active as

long as the device is in normal operation and is not

experiencing any faults. This output activates after a 10 ms

delay and must be pulled up by an external resistor to a

supply voltage (e.g., V_IN).

FUNCTIONAL INTERNAL BLOCK DESCRIPTION

System Control

& Logic

Internal Bias

Circuits

Oscillator

Control &

Supervisory

Functions

Tracking &

Sequencing

Protection

Functions

Buck Converter

Figure 4. 34713 Block Diagram

down commands. It communicates with the buck converter to

INTERNAL BIAS CIRCUITS

manage the switching operation and protects it against any

faults.

This block contains all circuits that provide the necessary

supply voltages and bias currents for the internal circuitry. It

consists of:

OSCILLATOR

• Internal Voltage Supply Regulator: This regulator

supplies the V_DDIvoltage that is used to drive the digital/

analog internal circuits. It is equipped with a Power-On-

Reset (POR) circuit that watches for the right regulation

levels. External filtering is needed on the VDDI pin. This

block will turn off during the shutdown mode.

• Internal Bandgap Reference Voltage: This supplies the

reference voltage to some of the internal circuitry.

• Bias Circuit: This block generates the bias currents

necessary to run all of the blocks in the IC.

This block generates the clock cycles necessary to run the

IC digital blocks. It also generates the buck converter

switching frequency. The switching frequency has a default

value of 1.0 MHz and can be programmed by connecting a

resistor divider to the FREQ pin, between VDDI and GND

pins (See Figure 1).

PROTECTION FUNCTIONS

This block contains the following circuits:

• Over Current Limit and Short Circuit Detection: This

block monitors the output of the buck converter for over

current conditions and short circuit events and alerts the

system control for further command.

• Thermal Limit Detection: This block monitors the

temperature of the device for overheating events. If the

temperature rises above the thermal shutdown

SYSTEM CONTROL AND LOGIC

This block is the brain of the IC where the device

processes data and reacts to it. Based on the status of the SD

pin, the system control reacts accordingly and orders the

device into the right status. It also takes inputs from all of the

monitoring/protection circuits and initiates power up or power

34713

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FUNCTIONAL DESCRIPTION

FUNCTIONAL INTERNAL BLOCK DESCRIPTION

threshold, this block will alert the system control for

further commands.

• Output Overvoltage and Undervoltage Monitoring: This

block monitors the buck converter output voltage to

ensure it is within regulation boundaries. If not, this

block alerts the system control for further commands.

during shutdown mode. Using this block along with

controlling the SD pin can offer the user power sequencing

capabilities by controlling when to turn the 34713 output on or

off.

BUCK CONVERTER

This block provides the main function of the 34713: DC to

DC conversion from an un-regulated input voltage to a

regulated output voltage used by the loads for reliable

operation. The buck converter is a high performance, fixed

frequency (externally adjustable), synchronous buck PWM

voltage-mode control. It drives integrated 45 mΩ N-channel

power MOSFETs saving board space and enhancing

efficiency. The switching regulator output voltage is

adjustable with an accuracy of less than ±2 % to meet today’s

requirements. Its output has the ability to track the voltage

applied at the VREFIN pin. The regulator's voltage control

loop is compensated using a type III compensation network,

with external components to allow for optimizing the loop

compensation, for a wide range of operating conditions. A

typical Bootstrap circuit with an internal PMOS switch is used

to provide the voltage necessary to properly enhance the

high-side MOSFET gate.

CONTROL AND SUPERVISORY FUNCTIONS

This block is used to interface with an outside host. It

contains the following circuits:

• Shutdown Control Input: An outside host can put the

34713 device into shutdown mode by sending a logic

“0” to the SD pin.

• Power Good Output Signal PG: The 34713 can

communicate to an external host that a fault has

occurred by releasing the drive on the PG pin high,

allowing the signal/pin to be pulled high by the external

pull-up resistor.

TRACKING AND SEQUENCING

This block allows the output of the 34713 to track the

voltage applied at the VREFIN pin in different tracking

configurations. This will be discussed in further details later in

this document. For power down during a shutdown mode, the

34713 uses internal discharge MOSFET (Figure 2) to

discharge the output. The discharge MOSFET is only active

The 34713 has the ability to supply up to 5.0 A of

continuous current, making it suitable for many high current

applications.

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FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

V_IN< 3.0V

SD = 0

Power Off

V_OUT= OFF

V_REF= OFF

PG = 1

Shutdown

V_OUT= Discharge

V_REF= Discharge

PG = 1

3.0V < = V_IN< = 6.0V

SD = 1

Short Circuit

V_OUT= OFF

V_REF= OFF

Overvoltage

V_OUT= ON

V_REF= ON

Normal

V_OUT= ON

V_REF= ON

V_OUT

< V_OV

t_TIMEOUTExpired

V_OUT

> V_OV

I_OUT> = I_SHORT

PG = 1

PG = 0

t

_TIMEOUTExpired

V_OUT> V_UV

Over Current

V_OUT= OFF

V_REF= ON

Undervoltage

V_OUT= ON

V_REF= ON

T_J< = 145°C &

_TIMEOUTExpired

I_OUT> = I_LIM

For > = 10ms

t

V_OUT< V_UV

Thermal

Shutdown

V_OUT= OFF

V_REF= OFF

PG = 1

T_J> = 170°C

Figure 5. Operation Modes Diagram

switching frequency and soft start values are determined by

reading the FREQ and ILIM pins respectively. A soft start

cycle is then initiated to ramp up the output of the buck

converter. The buck converter error amplifier uses the

voltage on the VREFIN pin as its reference voltage until

V_REFINis equal to 0.7 V, then the error amplifier defaults to

the internal 0.7 V reference voltage. This method helps

achieve multiple tracking configurations as will be explained

later in this document.

MODES OF OPERATION

The 34713 has two primary modes of operation:

Normal Mode

In normal mode, all functions and outputs are fully

operational. To be in this mode, the V_INneeds to be within its

operating range, Shutdown input is high, and no faults are

present. This mode consumes the most amount of power.

Soft start is used to prevent the output voltage from

overshooting during startup. At initial startup, the output

capacitor is at zero volts; V_OUT= 0 V. Therefore, the voltage

across the inductor will be PV_INduring the capacitor charge

phase which will create a very sharp di/dt ramp. Allowing the

inductor current to rise too high can result in a large

difference between the charging current and the actual load

current that can result in an undesired voltage spike once the

capacitor is fully charged. The soft start is active each time

the IC goes out of standby or shutdown mode, power is

recycled, or after a fault retry.

Shutdown Mode

In this mode, activated by pulling the SD pin low, the chip

is in a shutdown state and the output is disabled and

discharged. In this mode, the 34713 consumes the least

amount of power since almost all of the internal blocks are

disabled.

START-UP SEQUENCE

When power is first applied, the 34713 checks the status

of the SD pin. If the device is in a shutdown mode, no block

will power up and the output will not attempt to ramp. Once

the SD pin is released to enable the device, the V_DDIinternal

supply voltage and the bias currents are established and the

internal V_DDIPOR signal is also released. The rest of the

internal blocks will be enabled and the buck converter

After a successful start-up cycle where the device is

enabled, no faults have occurred, and the output voltage has

reached its regulation point, the 34713 pulls the power good

output signal low after a 10 ms reset delay, to indicate to the

host that the device is in normal operation.

34713

Analog Integrated Circuit Device Data

Freescale Semiconductor

12

FUNCTIONAL DEVICE OPERATION

PROTECTION AND DIAGNOSTIC FEATURES

The 34713 monitors the application for several fault

conditions to protect the load from overstress. The reaction of

the IC to these faults ranges from turning off the outputs to

just alerting the host that something is wrong. In the following

paragraphs, each fault condition is explained:

operation to limit the current, and a 10 ms over current limit

timer (t_LIM) starts. The converter will stay in this mode of

operation until one of the following occurs:

• The current is reduced back to the normal level before

t_LIMexpires, and in this case normal operation is

regained.

• t_LIMexpires without regaining normal operation, at

which point the device turns off the output and the

power good output signal is pulled high. At the end of a

time-out period of 100 ms (t_TIMEOUT), the device will

attempt another soft start cycle.

Output Overvoltage

An overvoltage condition occurs once the output voltage

goes higher than the rising overvoltage threshold (V_OVR). In

this case, the power good output signal is pulled high, alerting

the host that a fault is present, but the output will stay active.

To avoid erroneous overvoltage conditions, a 20 µs filter is

implemented. The buck converter will use its feedback loop

to attempt to correct the fault. Once the output voltage falls

below the falling overvoltage threshold (V_OVF), the fault is

cleared and the power good output signal is pulled low, the

device is back in normal operation.

• The device reaches the thermal shutdown limit (T_SDFET

)

and turns off the output. The power good output signal

is pulled high.

• The output current keeps increasing until it reaches the

short circuit current limit (I_SHORT). See below for more

details.

Output Undervoltage

Short Circuit Current Limit

An undervoltage condition occurs once the output voltage

falls below the falling undervoltage threshold (V_UVF). In this

case, the power good output signal is pulled high, alerting the

host that a fault is present, but the output will stay active. To

avoid erroneous undervoltage conditions, a 20 µs filter is

implemented. The buck converter will use its feedback loop

to attempt to correct the fault. Once the output voltage rises

above the rising undervoltage threshold (V_UVR), the fault is

cleared and the power good output signal is pulled low, the

device is back in normal operation.

This block uses the same current detection mechanism as

the over current limit detection block. If the load current

reaches the I_SHORTvalue, the device reacts by shutting down

the output immediately. This is necessary to prevent damage

in case of a permanent short circuit. Then, at the end of a

time-out period of 100 ms (t_TIMEOUT), the device will attempt

another soft start cycle.

Thermal Shutdown

Thermal limit detection block monitors the temperature of

the device and protects against excessive heating. If the

temperature reaches the thermal shutdown threshold

(T_SDFET), the converter output switches off and the power

good output signal indicates a fault by pulling high. The

device will stay in this state until the temperature has

decreased by the hysteresis value and then After a time-out

period (T_TIMEOUT) of 100 ms, the device will retry

Output Over Current

This block detects over current in the Power MOSFETs of

the buck converter. It is comprised of a sense MOSFET and

a comparator. The sense MOSFET acts as a current

detecting device by sampling a ratio of the load current. That

sample is compared via the comparator with an internal

reference to determine if the output is in over current or not.

If the peak current in the output inductor reaches the over

current limit (I_LIM), the converter will start a cycle-by-cycle

automatically and the output will go through a soft start cycle.

If successful normal operation is regained, the power good

output signal is asserted low to indicate that.

34713

Analog Integrated Circuit Device Data

Freescale Semiconductor

13

TYPICAL APPLICATIONS

PROTECTION AND DIAGNOSTIC FEATURES

TYPICAL APPLICATIONS

VIN

BOOT

VIN

BOOT

VDDI

C15

SW

I/O SIGNALS

4.7_nopop

VDDI

0.1uF

PVIN

J2

C14

U1

R16

0.1uF

PVIN

3

2

1

VIN

GND

R12

10k_nopop FREQ

R10

10k

1

2

3

4

5

6

18

17

16

15

14

13

J3

SGND

FREQ

ILIM

PG

PVIN

SW

ILIM

R11

10k

GND

VMASTER

VOUT

FREQ

3

2

1

R13

10k_nopop

SW

ILIM

PG

MC34713

PG

SW

N/C

GND

SD

GND

VMASTER PGOOD LED

SD

VMASTER

VIN

R7

VREFIN

R8

1k

10k

C11

VREFIN

D1

C13

0.1uF

LED

0.1uF

VOUT

R9

VOUT

10k

LED

INV

C12

0.1uF

COMP

JUMPERS

BUCK CONVERTER

VOUT1 VOUT2

L1

J1

SW

VOUT

PVIN

VMASTER

VREFIN

1

2

1

3

5

7

9

2

4

6

8

STBY_nopop

2

1.5uH

LED

PG

R3

1

D2

PMEG2010EA_nopop

C6

100uF

C7

100uF

C8

100uF

SD

10

4.7_nopop

C9

CON10A

2

1nF_nopop

SD

COMPENSATION NETWORK

PVIN CAPACITORS

OPTIONAL nopop

VOUT

VDDI

PVIN

ILIM

FREQ

C20

1nF

C1

0.1uF

C2

1uF

C3

100uF

C4

100uF

C5

100uF

R6

POT_50K_nopop

R5

POT_50K_nopop

R1

INV

20k

C18

COMP

R14

300

0.02nF

VIN CAPACITORS

R15

15k

C19

R2

VIN

12.7k

1.9nF

C17

C16

10uF

0.1uF

Figure 6. Typical Applications

34713

Analog Integrated Circuit Device Data

Freescale Semiconductor

14

TYPICAL APPLICATIONS

PROTECTION AND DIAGNOSTIC FEATURES

COMPONENT SELECTION

SWITCHING FREQUENCY SELECTION

The switching frequency defaults to a value of 1.0 MHz

when the FREQ pin is grounded, and 200 KHz when the

FREQ pin is connected to VDDI. Intermediate switching

frequencies can be obtained by connecting an external

resistor divider to the FREQ pin. The table below shows the

resulting switching frequency versus FREQ pin voltage.

where,

Maximum OFF time percentage

Switching period.

Table 5. Switching Frequency Adjustment

FREQUENCY

200

VOLTAGE APPLIED TO PIN FREQ

2.341 – 2.500

2.185 - 2.340

253

307

2.029 - 2.184

Drain – to – source resistance of FET

Winding resistance of Inductor

360

1.873 - 2.028

413

1.717 – 1.872

1.561 – 1.716

1.405 - 1.560

466

520

573

1.249 - 1.404

Output current ripple.

627

1.093 - 1.248

OUTPUT FILTER CAPACITOR

680

0.936 - 1.092

For the output capacitor, the following considerations are

more important than the actual capacitance value, the

physical size, the ESR and the voltage rating:

733

0.781 - 0.936

787

0.625 - 0.780

Transient Response percentage, TR_%

Maximum Transient Voltage, TR_v_dip = Vo*TR_%

Maximum current step,

840

0.469 - 0.624

893

0.313 - 0.468

947

0.157 - 0.312

1000

0.000 - 0.156

Inductor Current rise time,

where,

D_max = Maximum ON time percentage.

I_O= Rated output current.

Vin_min = Minimum input voltage at PV_IN

Figure 7. Resistor Divider for Frequency Adjustment

As a result, it is possible to calculate

SELECTION OF THE INDUCTOR

Inductor calculation is straight forward, being

34713

Analog Integrated Circuit Device Data

Freescale Semiconductor

15

TYPICAL APPLICATIONS

PROTECTION AND DIAGNOSTIC FEATURES

C_BOOT

L

BOOT

SW

Gate

Driver

F

C

SW

VOUT

O

In order to find the maximum allowed ESR,

R

S

R

O

C

S

INV

PWM

Comparitor

R_B

R

F

Ramp

Generator

C_X

C

F

Error

Amplifier

COMP

The effects of the ESR is often neglected by the designers

and may present a hidden danger to the ultimate supply

stability. Poor quality capacitors have widely disparate ESR

value, which can make the closed loop response

inconsistent.

V

DDI

REFIN

Reference

Selection

V

R_O

⎛

⎞

V_O= V_REF------- + 1

Bandgap

Regulator

⎝

⎠

R_B

34713

Figure 9. Type III Compensation Network

Consider the crossover frequency, F_CROSS, of the open loop

gain at one-sixth of the switching frequency, F_SW.

Then,

Io

Io_step

Current

⇒

response

Worst case

dt_I_rise

where R_Ois a user selected resistor. Knowing the LC

frequency, it can be obtained the values of R_Fand C_S:

assumption

Figure 8. Transient Parameters

TYPE III COMPENSATION NETWORK

Power supplies are desired to offer accurate and tight

regulation output voltages. To accomplish this requires a high

DC gain. But with high gain comes the possibility of instability.

The purpose of adding compensation to the internal error

amplifier is to counteract some of the gains and phases

contained in the control-to-output transfer function that could

jeopardized the stability of the power supply. The Type III

compensation network used for 34713 comprises two poles

(one integrator and one high frequency pole to cancel the

zero generated from the ESR of the output capacitor) and two

zeros to cancel the two poles generated from the LC filter as

shown in Figure 9.

This gives as a result,

&

Calculate Rs by placing the Pole 1 at the ESR zero

frequency:

34713

Analog Integrated Circuit Device Data

Freescale Semiconductor

16

TYPICAL APPLICATIONS

PROTECTION AND DIAGNOSTIC FEATURES

node, so it is not ground and it is floating and moving in

voltage, so we cannot just apply a voltage directly to the gate

of the high side that is referenced to ground, we need a

voltage referenced to the SW node. That is why the bootstrap

capacitor is needed for. This capacitor charges during the

high side off time, since the low side will be on during that

time, so the SW node and the bottom of the bootstrap

capacitor will be connected to ground and the top of the

capacitor will be connected to a voltage source, so the

capacitor will charge up to that voltage source (say 5V). Now

when the low side MOSFET switches off and the high side

MOSFET switches on, the SW nodes rises up to Vin, and the

voltage on the boot pin will be Vcap + Vin. So the gate of the

high side will have Vcap across it and it will be able to stay

enhanced. A 0.1µF capacitor is a good value for this

bootstrap element.

⇒

Equating the Pole 2 at Crossover Frequency to achieve a

faster response and a proper phase margin,

SOFT START SELECTION

Table 6 shows the voltage that should be applied to the

terminal ILIM to get the desired configuration of the soft start

timing.

Table 6. ILIM Table

Soft Start (ms)

Voltage Applied to ILIM

⇒

3.2

1.6

0.8

0.4

1.25 - 1.49

1.50 - 1.81

1.82 - 2.13

2.14 - 2.50

BOOTSTRAP CAPACITOR

The bootstrap capacitor is needed to supply the gate

voltage for the high side MOSFET. This N-Channel MOSFET

needs a voltage difference between its gate and source to be

able to turn on. The high side MOSFET source is the SW

34713

Analog Integrated Circuit Device Data

Freescale Semiconductor

17

PACKAGING

PACKAGING DIMENSIONS

PACKAGING

PACKAGING DIMENSIONS

EP SUFFIX

24-PIN

PLASTIC PACKAGE

98ARL10577D

ISSUE B

34713

Analog Integrated Circuit Device Data

Freescale Semiconductor

18

PACKAGING

PACKAGING DIMENSIONS

EP SUFFIX

24-PIN

PLASTIC PACKAGE

98ARL10577D

ISSUE B

34713

Analog Integrated Circuit Device Data

Freescale Semiconductor

19

REVISION HISTORY

REVISION

DATE

DESCRIPTION OF CHANGES

•

Pre-release version

Implemented Revision History page

2/2006

1.0

•

Initial release

11/2006

2.0

Converted format from Market Assessment to Product Preview

Major updates to the data, form, and style

2/2007

5/2007

•

Major updates to the data, form, and style

3.0

4.0

•

Changed Feature fom 2% to 1%, relabeled to include soft start

Changed 34713 Simplified Application Diagram

Made change to 34713 Simplified Internal Block Diagram

Removed Machine Model in Maximum Ratings

Changed Input DC Supply Current ⁽¹¹⁾Normal mode and Input DC Supply Current ⁽¹¹⁾Shutdown

mode

(14)

•

Changed Output Voltage Accuracy ⁽¹²⁾

,

Changed Soft start Adjusting reference Voltage Range and Short Circuit Current Limit

Changed High-Side N-CH Power MOSFET (M3) RDS(ON) ⁽¹²⁾and Low-Side N-CH Power

MOSFET (M4) RDS(ON) ⁽¹²⁾

•

Changed M2 RDS(ON) and PVIN Pin Leakage Current

Changed SD Pin Internal Pull Up Resistor ⁽¹⁵⁾

Changed Changed Soft Start Duration (Normal Mode)

Changed Over Current Limit Retry Time-out Period and Output Undervoltage/Overvoltage Filter

Delay Timer

•

Changed PG Reset Delay and Thermal Shutdown Retry Time-out Period ⁽¹⁶⁾

Changed definition for Soft Start Adjustment input (ILIM)

Changed drawings in Typical Applications

Changed drawing in Type III Compensation Network

Changed table for Soft Start Selection

Removed PC34713EP/R2 from the ordering information and added MC34713EP/R2

Changed the data sheet status to Advance Information

34713

Analog Integrated Circuit Device Data

Freescale Semiconductor

20

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MC34713

Rev. 4.0

5/2007