SM74202MM-2 [TI]

100V Current Mode PWM Controller;


型号：	SM74202MM-2
厂家：	TEXAS INSTRUMENTS
描述：	100V Current Mode PWM Controller
文件：	总14页 (文件大小：300K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

SM74202

SM74202 100V Current Mode PWM Controller

Literature Number: SNOSBA4

November 23, 2011

SM74202

100V Current Mode PWM Controller

General Description

Features

The SM74202 high voltage pulse-width-modulation (PWM)

controller contains all of the features needed to implement

single ended primary power converter topologies. Output volt-

age regulation is based on current-mode control, which eases

the design of loop compensation while providing inherent line

feed-forward. The SM74202 includes a high-voltage start-up

regulator that operates over a wide input range up to 100V.

The PWM controller is designed for high speed capability in-

cluding an oscillator frequency range to 1MHz and total prop-

agation delays less than 100ns. Additional features include

an error amplifier, precision reference, line under-voltage

lockout, cycle-by-cycle current limit, slope compensation,

softstart, oscillator synchronization capability and thermal

shutdown. The controller is available in the MSOP-10 pack-

age.

Renewable Energy Grade

■

Internal Start-up Bias Regulator

Error Amplifier

Precision Voltage Reference

Programmable Softstart

1A Peak Gate Driver

Maximum Duty Cycle Limiting (50%)

Programmable Line Under Voltage Lockout (UVLO) with

Adjustable Hysteresis

Cycle-by-Cycle Over-Current Protection

■

Programmable Oscillator Frequency with Synchronization

Capability

Current Sense Leading Edge Blanking

Thermal Shutdown Protection

■

Applications

Photovoltaic

■

Telecommunication Power Converters

Industrial Power Converters

+42V Automotive Systems

Typical Application Circuit

30160113

Non-Isolated Flyback Converter

301601

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Connection Diagram

Top View

30160101

10-Lead MSOP, LLP

Ordering Information

Order Number

Package Type

NSC Package Drawing NSC Package Marking

Supplied As

SM74202MM-2

MSOP-10

MUB10A

SD9B

1000 Units on Tape and

Reel

SM74202MME-2

SM74202MMX-2

250 Units on Tape and

Reel

3500 Units on Tape and

Reel

Pin Descriptions

Name

VIN

Description

Application Information

Source Input Voltage

Feedback Signal

Input to the start-up regulator. Input range is 13V to 100V.

Inverting input of the internal error amplifier. The non-

inverting input is internally connected to a 1.25V

reference.

COMP

VCC

The output of the error amplifier and input to the COMP pull-up is provided by an internal 5K resistor which

Pulse Width Modulator may be used to bias an opto-coupler transistor.

Output of the internal high voltage series pass If an auxiliary winding raises the voltage on this pin above

regulator. Regulated output voltage is 7.7V

the regulation set point, the internal series pass regulator

will shut down, reducing the internal power dissipation.

OUT

GND

Output of the PWM controller

Ground return

Gate driver output with a 1A peak current capability.

UVLO

Line Under-Voltage Shutdown

An external resistor divider from the power converter

source voltage sets the shutdown levels. The threshold at

this pin is 1.25V. Hysteresis is set by a switched internal

20µA current source.

Current Sense input

Current sense input for current mode control and over-

current protection. Current limiting is accomplished using

a dedicated current sense comparator. If the CS pin

voltage exceeds 0.5V the OUT pin switches low for cycle-

by-cycle current limiting. CS is held low for 50ns after OUT

switches high to blank leading edge current spikes.

RT / SYNC Oscillator timing resistor pin and synchronization An external resistor connected from RT to GND sets the

input

oscillator frequency. This pin also accepts

synchronization pulses from an external clock.

Softstart Input

An external capacitor and an internal 10µA current source

set the soft-start ramp rate.

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Storage Temperature

Junction Temperature

-65°C to +150°C

150°C

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,

please contact the Texas Instruments Sales Office/

Distributors for availability and specifications.

Operating Ratings

VIN Voltage

External Voltage applied to VCC

Operating Junction Temperature

13V to 90V

8V to 15V

-40°C to +125°C

VIN to GND

-0.3V to 100V

VCC to GND

-0.3V to 16V

-0.3V to 7V

Internally Limited

All other pins to GND

Power Dissipation

ESD Rating (Note 2)

Human Body Model

2kV

Electrical Characteristics

Specifications in standard type face are for T_J= +25°C and those in boldface type apply over the full operating junction temperature

range. Unless otherwise specified: VIN = 48V, VCC = 10V, and RT = 31.6kΩ. (Note 3)

Symbol

Parameter

Conditions

V_CC= Open

Min

Typ

Max

8.0

Units

Startup Regulator

V_CCReg

V_CCRegulation

V_CCCurrent Limit

7.4

7.7

(Note 4)

µA

I-V_IN

Startup Regulator Leakage

Shutdown Current

V_IN= 100V

150

250

500

350

I_IN

V_UVLO= 0V, V_CC= open

VCC Supply

V_CCUVLO (Rising)

VccReg

- 300mV

VccReg -

100mV

V_CCUVLO (Falling)

Supply Current

5.3

6.0

6.7

I_CC

Cload = 0

Error Amplifier

GBW

Gain Bandwidth

MHz

DC Gain

Reference Voltage

COMP Sink Capability

FB = COMP

1.225

1.25

1.275

FB = 1.5V COMP= 1V

UVLO Pin

Shutdown Threshold

1.25

Undervoltage Shutdown

Hysteresis Current Source

µA

Current Limit

ILIM Delay to Output

CS step from 0 to 0.6V

Time to onset of OUT

Transition (90%)

Cycle by Cycle CS Threshold

Voltage

0.5

Leading Edge Blanking Time

CS Sink Impedance (clocked)

Ω

Soft Start

Softstart Current Source

Softstart to COMP Offset

µA

0.35

0.55

0.75

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Symbol

Parameter

Conditions

(Note 5)

Min

Typ

Max

Units

Oscillator

Frequency1 (RT = 31.6k)

Frequency2 (RT = 9.76k)

Sync threshold

175

560

2.4

200

630

3.2

225

700

3.8

kHz

(Note 5)

PWM Comparator

Delay to Output

COMP set to 2V,

CS stepped 0 to 0.4V,

Time to onset of OUT

transition low

Min Duty Cycle

COMP=0V

Max Duty Cycle

0.33

5.2

COMP to PWM Comparator Gain

COMP Open Circuit Voltage

COMP Short Circuit Current

4.3

0.6

6.1

1.5

COMP=0V

1.1

Output Section

Output High Saturation

Output Low Saturation

Rise Time

Iout = 50mA, V_CC- V_OUT

I_OUT= 100mA, V_OUT

Cload = 1nF

0.25

0.75

0.25

Fall Time

Cload = 1nF

Thermal Shutdown

Tsd

Thermal Shutdown Temp.

165

°C

Thermal Shutdown Hysteresis

Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the

device is intended to be functional. For guaranteed specifications and test conditions, see the Electrical Characteristics.

Note 2: The human body model is a 100 pF capacitor discharged through a 1.5kΩ resistor.

Note 3: Limits are 100% production tested at 25°C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality

Control (SQC) methods. The limits are used to calculate National's Average Outgoing Quality Level (AOQL).

Note 4: Device thermal limitations may limit usable range.

Note 5: Specification applies to the oscillator frequency. The operational frequency of the SM74202 is divided by two.

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Typical Performance Characteristics Unless otherwise specified: T_J= 25°C.

V_CCand V_INvs V_IN

V_CCvs I_CC(V_IN= 48V)

30160106

30160107

Oscillator Frequency vs RT (Note 5)

Oscillator Frequency vs Temperature

RT = 31.6kΩ (Note 5)

30160108

30160109

Soft Start Current vs Temperature

Error Amp. Gain/Phase Plot

30160110

30160121

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Block Diagram

30160102

FIGURE 1.

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UVLO hysteresis is accomplished with an internal 20µA cur-

rent source that is switched on or off into the impedance of

the set-point divider. When the UVLO threshold is exceeded,

the current source is activated to instantly raise the voltage at

the UVLO pin. When the UVLO pin voltage falls below the

1.25V threshold the current source is turned off, causing the

voltage at the UVLO pin to fall. The UVLO pin can also be

used to implement a remote enable / disable function. If an

external transistor pulls the UVLO pin below the 1.25V thresh-

old, the converter is disabled.

Detailed Operating Description

The SM74202 High Voltage PWM controller contains all of the

features needed to implement single ended primary power

converter topologies. The SM74202 includes a high-voltage

startup regulator that operates over a wide input range to

100V. The PWM controller is designed for high speed capa-

bility including an oscillator frequency range to 1MHz and total

propagation delays less than 100ns. Additional features in-

clude an error amplifier, precision reference, line under-volt-

age lockout, cycle-by-cycle current limit, softstart, oscillator

sync capability and thermal shutdown. The functional block

diagram of theSM74202 is shown in Figure 1. The SM74202

is designed for current-mode control power converters, which

require a single drive output, such as Flyback and Forward

topologies. The SM74202 provides all of the advantages of

current-mode control including line feed-forward, cycle-by-

cycle current limiting and simplified loop compensation .

Error Amplifier

An internal high gain error amplifier is provided within the

SM74202. The amplifier's non-inverting input is internally set

to a fixed reference voltage of 1.25V. The inverting input is

connected to the FB pin. In non-isolated applications, the

power converter output is connected to the FB pin via voltage

scaling resistors. Loop compensation components are con-

nected between the COMP and FB pins. For most isolated

applications the error amplifier function is implemented on the

secondary side of the converter and the internal error ampli-

fier is not used. The internal error amplifier is configured as

an open drain output and can be disabled by connecting the

FB pin to ground. An internal 5K pull-up resistor between a

5V reference and COMP can be used as the pull-up for an

optocoupler in isolated applications.

High Voltage Start-Up Regulator

The SM74202 contains an internal high voltage startup reg-

ulator, that allows the input pin (Vin) to be connected directly

to line voltages as high as 100V. The regulator output is in-

ternally current limited to 15mA. When power is applied, the

regulator is enabled and sources current into an external ca-

pacitor connected to the V_CCpin. The recommended capac-

itance range for the Vcc regulator is 0.1µF to 100µF. When

the voltage on the V_CCpin reaches the regulation level of

7.7V, the controller output is enabled. The controller will re-

main enabled until V_CCfalls below 6V.

Current Limit/Current Sense

The SM74202 provides a cycle-by-cycle over current protec-

tion function. Current limit is accomplished by an internal

current sense comparator. If the voltage at the current sense

comparator input exceeds 0.5V, the output is immediately

terminated. A small RC filter, located near the controller, is

recommended to filter noise from the current sense signal.

The CS input has an internal MOSFET which discharges the

CS pin capacitance at the conclusion of every cycle. The dis-

charge device remains on an additional 50ns after the begin-

ning of the new cycle to attenuate the leading edge spike on

the current sense signal.

In typical applications, a transformer auxiliary winding is con-

nected through a diode to the V_CCpin. This winding should

raise the V_CCvoltage above 8V to shut off the internal startup

regulator. Powering V_CCfrom an auxiliary winding improves

conversion efficiency while reducing the power dissipated in

the controller. The external V_CCcapacitor must be selected

such that the capacitor maintains the Vcc voltage greater than

the V_CCUVLO falling threshold (6V) during the initial start-up.

During a fault condition when the converter auxiliary winding

is inactive, external current draw on the V_CCline should be

limited such that the power dissipated in the start-up regulator

does not exceed the maximum power dissipation capability of

the controller.

The SM74202 current sense and PWM comparators are very

fast, and may respond to short duration noise pulses. Layout

considerations are critical for the current sense filter and

sense resistor. The capacitor associated with the CS filter

must be located very close to the SM74202 and connected

directly to the pins of the controller (CS and GND). If a current

sense transformer is used, both leads of the transformer sec-

ondary should be routed to the sense resistor and the current

sense filter network. A sense resistor located in the source of

the primary power MOSFET may be used for current sensing,

but a low inductance resistor is required. When designing with

a current sense resistor all of the noise sensitive low power

ground connections should be connected together local to the

controller and a single connection should be made to the high

current power ground (sense resistor ground point).

An external start-up or other bias rail can be used instead of

the internal start-up regulator by connecting the V_CCand the

Vin pins together and feeding the external bias voltage

(8-15V) to the two pins.

Line Under Voltage Detector

The SM74202 contains a line Under Voltage Lock Out (UV-

LO) circuit. An external set-point voltage divider from Vin to

GND sets the operational range of the converter. The resistor

divider must be designed such that the voltage at the UVLO

pin is greater than 1.25V when Vin is in the desired operating

range. If the under voltage threshold is not met, all functions

of the controller are disabled and the controller remains in a

low power standby state.

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COMP pin will result in a zero duty cycle at the controller out-

put.

Oscillator and Sync Capability

A single external resistor connected between the RT and

GND pins sets the SM74202 oscillator frequency. Internal to

the device is an oscillator divide by two circuit. This divide by

two circuit creates an exact 50% duty cycle limit function. Be-

cause of this, the internal oscillator actually operates at twice

the frequency of the output (OUT). To set a desired output

operational frequency (F), the RT resistor can be calculated

from:

Soft Start

The softstart feature allows the power converter to gradually

reach the initial steady state operating point, thereby reducing

start-up stresses and current surges. At power on, after the

V_CCand the line undervoltage lockout thresholds are satis-

fied, an internal 10µA current source charges an external

capacitor connected to the SS pin. The capacitor voltage will

ramp up slowly and will limit the COMP pin voltage and the

duty cycle of the output pulses.

Gate Driver and Maximum Duty

Cycle Limit

The SM74202 provides an internal gate driver (OUT), which

can source and sink a peak current of 1 Amp. The maximum

output duty cycle is precisely equal to 50%. The maximum

duty cycle function is accomplished with an internal toggle flip-

flop which ensures an accurate duty cycle limit. The internal

oscillator frequency is therefore twice the operating frequency

of the PWM controller (OUT pin).

The SM74202 can also be synchronized to an external clock.

The external clock must have a higher frequency than the free

running oscillator frequency set by the RT resistor. The clock

signal should be capacitively coupled into the RT pin through

a 100pF capacitor. A peak voltage level greater than 3.7 Volts

at the RT pin is required for detection of the sync pulse. The

sync pulse width should be set between 15 to 150ns by the

external components. The RT resistor is always required,

whether the oscillator is free running or externally synchro-

nized. The voltage at the RT pin is internally regulated at 2

Volts. The RT resistor should be located very close to the de-

vice and connected directly to the pins of the controller (RT

and GND).

Thermal Protection

Internal thermal shutdown circuitry is provided to protect the

integrated circuit in the event the maximum junction temper-

ature is exceeded. This feature prevents catastrophic failures

from accidental device overheating. When activated, typically

at 165 degrees Celsius, the controller is forced into a low

power standby state, disabling the output driver and the bias

regulator. After the temperature is reduced (typical hysteresis

= 25°C) the V_CCregulator is enabled and a softstart sequence

initiated.

PWM Comparator

The PWM comparator compares the current ramp signal with

the loop error voltage derived from the error amplifier output.

The error amplifier output voltage at the COMP pin is offset

by 1.4V and then further attenuated by a 3:1 resistor divider.

The PWM comparator polarity is such that 0 Volts on the

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Typical Application Circuit: 36V - 75 V_INand 3.3V, 4.5A OUT

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Bill Of Materials

ITEM

PART NUMBER

C4532X7R2A225M

DESCRIPTION

CAPACITOR, CER, TDK

CAPACITOR, CER, KEMET

CAPACITOR, CER, TDK

VALUE

2.2µF, 100V

C4532X7R2A225M

C2012X7R1H103K

C3216X7R2A104K

C2012X7R1H103K

C2012C0G1H221J

C2012C0G1H332J

C2012C0G1H101J

C2012X7R1H104K

C3216X7R1C475K

C2012C0G1H102J

C2012C0G1H471J

C4532X7S0G107M

A700X277M0004AT

CMPD2838E-NSA

MBRD835L

2.2µF, 100V

0.01µF, 50V

0.1µF, 100V

0.01µF, 50V

220pF, 50V

3300pF, 50V

100pF, 50V

0.1µF, 50V

4.7µF, 16V

1000pF, 50V

470p, 50V

100µF, 4V

CAPACITOR, ALUM ORGANIC, KEMET 270µF, 4V

DIODE, SIGNAL, CENTRAL

DIODE, RECTIFIER, ON

SEMICONDUCTOR

MKDS 1/2-3.81

TERM BLK, MINI, 2 POS, PHOENIX

CONTACT

TERM BLK, MINI, 2 POS, PHOENIX

CONTACT

SI7898DP

FET, SILICONIX

RESISTOR

150V, 85mΩ

CRCW120610R0F

CRCW12066192F

CRCW08052871F

CRCW08051001F

CRCW08051502F

CRCW08051242F

CRCW08051000F

CRCW12060R47F

CRCW251210R0F

CRCW08052431F

CRCW08051471F

CRCW080520R0F

B0695-A COILCRAFT

61.9kΩ

2.87kΩ

1.00kΩ

15.0kΩ

12.4kΩ

100

0.47

10, 1W

2.43K

1.47K

TRANSFORMER, FLYBACK, EFD20

CORE

PA0751 PULSE

SM74202MM-2

1SMB5936B

TRANSFORMER, FLYBACK, EFD20

CORE

ALTERNATE

CONTROLLER, SINGLE OUT, PWM,

NATIONAL

DIODE, ZENER, SMB, 30V

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Physical Dimensions inches (millimeters) unless otherwise noted

10 Lead MSOP Package

NS Package Number MUB10A

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Notes

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SM74202MM-2 [TI]

相关型号：

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