NCP5173

http://onsemi.com

4

Characteristic

Test Conditions

Min

Typ

Max

Unit

General

Operating Current

−

5.5

8.0

mA

Shutdown Mode Current

−

−

12

−

60

100

mA

Minimum Operation Input Voltage

−

2.45

2.70

V

Thermal Shutdown

(Note 3)

150

180

210

°C

Thermal Hysteresis

(Note 3)

−

25

−

°C

3. Guaranteed by design, not 100% tested in production.

PIN FUNCTION DESCRIPTION

Pin Number

Symbol

Function

1

pensation, current limit and soft−start. Loop compensation can be implemented by a simple RC

network as shown in the application diagram on Page 2 as R1 and C1.

2

FB

Positive regulator feedback pin. This pin senses a positive output voltage and is referenced to

1.276 V. When the voltage at this pin falls below 0.4 V, chip switching frequency reduces to 20% of

the nominal frequency.

3

Test

These pins are connected to internal test logic and should either be left floating or tied to ground.

Connection to a voltage between 2.0 V and 6.0 V shuts down the internal oscillator and leaves the

power switch running.

4

SS

Synchronization and shutdown pin. This pin may be used to synchronize the part to nearly twice

the base frequency. A TTL low will shut the part down and put it into low current mode. If synchro-

nization is not used, this pin should be either tied high or left floating for normal operation.

5

Input power supply pin. This pin supplies power to the part and should have a bypass capacitor

connected to AGND.

6

AGND

Analog ground. This pin provides a clean ground for the controller circuitry and should not be in the

path of large currents. The output voltage sensing resistors should be connected to this ground pin.

This pin is connected to the IC substrate.

7

PGND

Power ground. This pin is the ground connection for the emitter of the power switching transistor.

Connection to a good ground plane is essential.

8

High current switch pin. This pin connects internally to the collector of the power switch. The open

voltage across the power switch can be as high as 40 V. To minimize radiation, use a trace as short

as practical.