TC120

DS21365B-page 4

© 2002 Microchip Technology Inc.

2.0

PIN DESCRIPTIONS

The descriptions of the pins are listed in Table 2-1.

TABLE 2-1:

PIN FUNCTION TABLE

Pin No.

(8-Pin SOP)

Symbol

Description

Unregulated supply input.

2

EXTW

Extended external switching transistor drive output. This output follows the timing on the EXT

output with an additional 100nsec blanking time on both the leading and trailing edges. That is,

this output transitions from high-to-low 100 nsec prior to the same transition on EXT; and

transitions low-to-high 100nsec after the same transition on EXT; resulting in a longer external

switch ON time. (See Section 3.9 External Switching Transistor Selection).

3

CPC

Charge pump capacitor input. An inverting charge pump is formed by attaching a capacitor and

diode to this input. (See Section 3.5 Improving High Load Efficiency In Regulator Operating

Mode).

4

SHDN/SS

Shutdown and soft-start control input. A soft start capacitor of 100pF (min) must be connected to

this input. The soft start capacitor is charged by an internal

µA current source that gently ramps

the TC120 into service. Shutdown control is best implemented with an external open collector (or

open drain) switch. The TC120 enters shutdown when this input is low. During shutdown, the

regulator is disabled, and supply current is reduced to less than 2.5

µA. Normal operation is

restored when this input is open-circuited, and allowed to float high. (See Section 3.6 Low Power

Shutdown Mode/Soft Start Input).

5

SENSE

Voltage sense input. This input must be connected to the output voltage node at the physical

location that requires the tightest voltage regulation.

6

GND

Ground terminal.

7

EXT

External switching transistor drive output. This output connects directly to the gate of an external

P-channel MOSFET for applications requiring output currents greater than 600mA. The timing of

this output exactly matches that of the gate drive for the internal P-channel transistor. This output

can drive a maximum capacitance of 1000pF. (See Section 3.9 External Switching Transistor

Selection).

8

Lx

Inductor terminal. This pin is connected to the drain of the internal P-channel switching transistor.

If the TC120 is operated as a regulator (i.e., using the internal switch); the inductor must be

connected between this pin and the SENSE pin.