TC2575

1.0A Step-Down Switching Regulator

4

TC2575-1 3/13/00

REPRESENTATIVE BLOCK DIAGRAM AND TYPICAL APPLICATION

TC2575

+

–

+

–

3.1V Internal

Regulator

ON/OFF

ON/OFF

Latch

Freq.

Shift

18kHz

Reset

Thermal

Shutdown

5

2

1.0 Amp

Switch

D1

L1

COUT

+VIN

CIN

VOUT

Driver

Output

GND

4

1

For Adjustable version

R1 = open, R2 = 0

Ω

Load

Regulated

Output

Feedback

Unregulated

DC Input

R2

R1

1.0k

Current

Limit

Comparator

Fixed gain

Error Amplifier

+

+

+

–

52kHz

Oscillator

1.235V

Band-Gap

Reference

3

Output

Voltage Versions

3.3V

5.0V

12V

15V

R2 (

Ω)

1.7k

3.1k

8.84k

11.3k

PIN DESCRIPTION

Pin No.

5-Pin TO-220

Symbol

Description

This pin is the positive input supply for the TC2575 step-down

switching regulator. In order to minimize voltage transients and to

supply the switching currents needed by the regulator, a suitable

2

Output

This is the emitter of the internal switch. The saturation voltage

mind that the PCB area connected to this pin should be kept to a

minimum in order to minimize coupling to sensitive circuitry.

3

GND

Circuit ground pin. See the information about the printed circuit

boad layout.

4

Feedback

This pin senses regulated output voltage to complete the

feedback loop. The signal is divided by the internal resistor

divider network R2, R1 and applied to the non-inverting input of

the internal error amplifier. In the adjustable version of the

TC2575 switching regulator this pin is the direct input of the error

amplifier and the resistor network R2, R1 is connected externally

to allow programming of the output voltage.

5

ON/OFF

It allows the switching regulator circuit to be shut down using

logic level signals, thus dropping the total input supply current to

approximately 80

µA. The threshold voltage is typically 1.4V.

regulator off. If the voltage applied to this pin is lower than 1.4V

or if this pin is left open, the regulator will be in the "on" condition.