4-119

TELCOM SEMICONDUCTOR, INC.

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TC170

CMOS CURRENT MODE PWM CONTROLLER

FEATURES

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Low Supply Current With

CMOS Technology ................................. 3.8mA Max

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Internal Reference ............................................. 5.1V

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Dual Push-Pull Outputs

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Direct-Power MOSFET Drive

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High Totem-Pole Output Drive .................... 300mA

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Differential Current-Sense Amplifier

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Programmable Current Limit

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Soft-Start Operation

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Double-Pulse Suppression

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Undervoltage Lockout

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Wide Supply Voltage Operation ............... 8V to16V

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High Frequency Operation .......................... 200kHz

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Available with Low OFF State Outputs

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Low Power, Pin-Compatible Replacement for UC3846

ORDERING INFORMATION

Temperature

Part No.

Package

Range

TC170COE

16-Pin SOIC (Wide)

0

°C to +70°C

TC170CPE

16-Pin Plastic DIP (Narrow) 0

°C to +70°C

GENERAL DESCRIPTION

The TC170 brings low-power CMOS technology to the

current-mode-switching power supply controller market.

Maximum supply current is 3.8 mA. Bipolar current-mode

control integrated circuits require five times more operating

current.

The dual totem-pole CMOS outputs drive power

MOSFETs or bipolar transistors. The 50nsec typical output

rise and fall times (1000pF capacitive loads) minimize

MOSFET power dissipation. Output peak current is 300mA.

The TC170 contains a full array of system-protection

circuits (see features).

Current-mode control lets users parallel power supply

modules. Two or more TC170 controllers can be slaved

together for parallel operation. Circuits can operate from a

master TC170 internal oscillator or an external system

oscillator.

The TC170 operates from an 8V to 16V power supply.

An internal 2%, 5.1V reference minimizes external compo-

nent count. The TC170 is pin compatible with the Unitrode

UC1846/2846/3846 bipolar controller.

Other advantages inherent in current-mode control in-

clude superior line and load regulation and automatic sym-

metry correction in push-pull converters.

5.1-VOLT

REFERENCE

OSCILLATOR

× 3.15 CURRENT

AMPLIFIER

PWM

COMPARATOR

POSITIVE

FEEDBACK

15

9

10

3

4

7

5

8

6

VIN

SYNC

(–) CURRENT

SENSE INPUT

(+) CURRENT

SENSE INPUT

COMP

(+) ERROR

AMP INPUT

(–) ERROR

AMP INPUT

ERROR

AMPLIFIER

100µA

0.75V

LIMIT BUFFER

AMPLIFIER

Q4

350mV

LOCK-UP

AMPLIFIER

Q3

Q1

Q2

3.5k

Ω

SHUTDOWN

COMPARATOR

350

mV

6k

Ω

SHUTDOWN

CURRENT LIMIT/

SOFT-START ADJUST

NOTE: Outputs low in

OFF state.

16

1

S

S

R

Q

C

DQ

Q

GROUND

VDD

OUTPUT

A (

)

12

14

11

13

PWM LATCH

TC170

VREF

2

–

+

RO

CO

VDD

+

–

–

+

+

–

+

–

+

–

UNDERVOLTAGE

LOCKOUT

OUTPUT

B (

)

TC170-5 10/1/96

FUNCTIONAL BLOCK DIAGRAM