LTC1440(RevC) View Datasheet(PDF) - Linear Technology

Part Name

Description

Manufacturer

LTC1440
(Rev.:RevC)

Ultralow Power Single/Dual Comparator with Reference

Linear Technology 

LTC1440/LTC1441/LTC1442

APPLICATIONS INFORMATION

LTC1440/LTC1441/LTC1442 are a family of micropower

comparators with built-in 1.182V reference. Features

include programmable hysteresis (LTC1440/LTC1442),

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

reference to drive up to a 0.01µF capacitor without oscil-

lation. The comparators’ CMOS outputs can source up to

40mA and the supply current glitches, that normally occur

when switching logic states, have been eliminated.

Power Supplies

The comparator family operates from a single 2V to 11V

supply. The LTC1440 includes a separate ground for the

comparator output stage, allowing a split supply ranging

from ±1V to ±5.5V. Connecting V – to GND on the LTC1440

will allow single supply operation. If the comparator out-

put 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 sup-

ply 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.

capacitor of up to 0.01µF without oscillation and by

inserting a series resistor, capacitance values up to 100µF

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.

Figure 3 shows the bypassed reference output with a

square wave applied to the V + pin. Resistors R2 and R3 set

10mV of hysteresis voltage band while R1 damps the

reference response. Note that the comparator output

doesn’t trip.

REFERENCE

OUTPUT

R1

REF

LTC144X

C1

V–

1440/1/2 F01

Figure 1. Damping the Reference Output

Comparator Outputs

The LTC1440 comparator output swings between GND

1000

and V + to assure TTL compatibility with a split supply. The

LTC1441 and LTC1442 outputs swing between V – and V +.

100

The outputs are capable of sourcing up to 40mA and

sinking up to 5mA while still maintaining microampere

10

quiescent currents. The output stage does not generate

crowbar switching currents during transitions which helps

minimize parasitic feedback through the supply pins.

1

Voltage Reference

The internal bandgap reference has a voltage of 1.182V

referenced to V –. The reference accuracy is 1.5% from

– 40°C to 85°C. It can source up to 200µA and sink up to

20µA with a 5V supply. The reference can drive a bypass

0.1

0.001

0.01

0.1

1

CAPACITOR VALUE (µF)

10

1440/1/2 F02

Figure 2. Damping Resistance vs Bypass Capacitor Value

10

144012fc

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