LTC1540I View Datasheet(PDF) - Linear Technology

Part Name

Description

Manufacturer

LTC1540I

Nanopower Comparator with Reference

Linear Technology 

LTC1540

PIN FUNCTIONS

GND (Pin 1): Ground. Connect to V – for single supply

operation.

V – (Pin 2): Negative Supply. Potential should be more

negative than GND. Connect to ground for single supply

operation.

IN + (Pin 3): Noninverting Comparator Input. Input com-

mon mode range from V – to V + – 1.3V. Input current

typically 10pA at 25°C.

IN – (Pin 4): Inverting Comparator Input. Input common

mode range from V – to V + – 1.3V. Input current typically

10pA at 25°C.

HYST (Pin 5): Hysteresis Input. Connect to REF if not

used. Input voltage range is from VREF to VREF – 50mV.

REF (Pin 6): Reference Output. 1.182V with respect

to V –. Can source up to 1mA and sink 10µA at 25°C. Drive

0.01µF bypass capacitor without oscillation.

V + (Pin 7): Positive Supply operating voltage is from 2V

to 11V.

OUT (Pin 8): Comparator CMOS Output. Swings from

GND to V +. Output can source up to 40mA and sink 5mA.

1

GND

2 V–

3 IN+

4 IN–

LTC1540

+

–

OUT 8

V+ 7

REF 6

HYST 5

1540 • PD

APPLICATIONS INFORMATION

The LTC1540 is a nanopower comparator with a built-in

1.182V reference. Features include programmable hyster-

esis, wide supply voltage range (2V to 11V) and the ability

of the reference to drive up to a 0.01µF capacitor without

oscillation. The comparator’s CMOS outputs can source

up to 40mA while supply current glitches that normally

occur when switching logic states, have been eliminated.

Power Supplies

The comparator operates from a single 2V to 11V supply.

The LTC1540 includes a separate ground for the compara-

tor output stage, allowing a split supply ranging from ±1V

to ±5.5V. Connecting V – to GND will allow single supply

operation. If the comparator output is required to source

more than 1mA, or the supply source impedance is high,

V + should be bypassed with a 0.1µF capacitor.

Comparator Inputs

The comparator inputs can swing from the negative supply,

V –, to within 1.3V (max) of the positive supply V+. The

inputs can be forced 300mV below V– or above V+ without

damage and the typical input leakage current is only ±10pA.

Comparator Output

The comparator output swings between GND and V + to

assure TTL compatibility with a split supply. The output is

capable of sourcing up to 40mA and sinking up to 5mA

while still maintaining nanoampere quiescent currents.

The output stage does not generate crowbar switching

currents during transitions which helps minimize parasitic

feedback through the supply pins.

Voltage Reference

The internal bandgap reference has a voltage of 1.182V

referenced to V –. The reference accuracy is ±2.0% from

0°C to 70°C. It can source up to 1mA and sink up to 10µA

with a 5V supply. The reference can drive a bypass

capacitor of up to 0.01µF without oscillation and by

inserting a series resistor, capacitance values up to 10µF

can be used (Figure 1).

Figure 2 shows the resistor value required for different

capacitor values to achieve critical damping. Bypassing

the reference can help prevent false tripping of the com-

parators by preventing glitches on V + or reference load

transients from disturbing the reference output voltage.

sn1540 1540fas

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