APPLICATIONS INFORMATION

Enable Control

A TTL compatible input is provided to allow the

regulator to be shut down. A low voltage on the Enable

pin puts the device into shutdown mode. In this mode

the regulator circuit is switched off and the quiescent

current reduces to virtually zero (typically less than

10nA). A high voltage on the Enable pin ensures

normal operation.

an independent source of up to 10V maximum. (e.g.

CMOS logic) for normal operation. There is no clamp

at any voltage within its operating range irrespective of

the voltage on the Enable pin.

Current Limit

The ZXCL devices include a current limit circuit which

restricts the maximum output current flow to typically

230mA. Practically the range of over-current should be

considered as minimum 160mA to maximum 800mA.

The device’s robust design means that an output short

tolerated for an indefinite period.

Thermal Overload

Thermal overload protection is included on chip. When

the device junction temperature exceeds a minimum

125°C the device will shut down. The sense circuit will

re-activate the output as the device cools. It will then

cycle until the overload is removed. The thermal

overload protection will be activated when high load

currents or high input to output voltage differentials

cause excess dissipation in the device.

Start up delay

A small amount of hysteresis is provided on the Enable

pin to ensure clean switching. This feature can be used

to introduce a start up delay if required. Addition of a

simple RC network on the Enable pin provides this

function. The following diagram illustrates this circuit

connection. The equation provided enables calculation

of the delay period.

ISSUE 5 - NOVEMBER 2001

8

ZXCL250 ZXCL260 ZXCL280

ZXCL300 ZXCL330 ZXCL400

R

C

Figure 1 Circuit Connection

T

= RCIn

V

V1.5

d(NOM)

IN













Calculation of start up delay as above