ZLDO500

FUNCTIONAL DESCRIPTION

The ZLDO is a high performance, ultra low

dropout, low quiescent regulator. Available in

SM8 surface mount packaging, the device is

able to dissipate 2W(note 1) allowing

complete design flexibility with an input span

upto 20V and 300mA output current. The

device quiescent is 1mA (typ) at 300mA load

current. A low battery comparator signifies

impending battery failure, whilst a shutdown

function reduces quiescent current to a mere

11

µA (typ). A precision bandgap reference

gives

± 2.5% output tolerance and good

temperature characteristics over the range

-40 to +85°C. AC performance is enhanced via

the use of a small external capacitor.

PIN DEFINITIONS

Pin 1

LBF - Low Battery Flag.

An open

collector NPN output which pulls low on failing

input supply.

Pin 2

SC - Shutdown Control. This high

impedance logic compatible input disables the

regulator when taken high. It includes a diode

wired to Vin and so will pass current if taken

more than 0.5V above Vin.

Pin 3

Vin - Voltage Input. The power supply to

the regulator. The permissible input voltage

range is -0.3 to 20V. An input capacitor is not

mandatory but will be useful in reducing the

coupling of noise from input to output and

minimising the effect of sudden changes in load

current on the input voltage.

Pin 4

N/C - Not Connected. Not internally

connected and so can be left open or wired to

any pin without affecting the performance of the

regulator.

Pin 5

Vout - Voltage Output. The output of the

regulator. An output capacitor of 1uF or greater

and having low ESR should be wired in close

proximity to the regulator to ensure stability for

all loads.

Pin 6

D/C - Do Not Connect. This pin is wired

to an internal circuit node of the regulator. No

external connection should be made to this pin.

Pin 7

Gnd - Ground. The ground connection

of the regulator against which the output

voltage is referenced.

Pin 8

Spg - Shaping. The shaping node for

the error amplifier of the regulator. A

capacitor of 10pF wired from this pin to the

output pin (pin 5) gives optimum stability.

Improved AC can be achieved by reducing

the value of this capacitor but stability may

be impaired for some load conditions.

NOTES.

1. Maximum power dissipation of the device is calculated assuming the package is mounted on a

PCB measuring 2 inches square.

2 Output voltage temperature coefficient is calculated as:-

3. Dropout voltage is defined as the input to output voltage differential at which the circuit ceases

4. Guaranteed by design.

4-82