LT1721CS datasheet(3/28 Pages) LINER

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LT1720/LT1721

ELECTRICAL CHARACTERISTICS The q denotes specifications that apply over the full operating temperature

range, otherwise specifications are at TA = 25°C. VCC = 5V, VCM = 1V, COUT = 10pF, VOVERDRIVE = 20mV, unless otherwise specified.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Input Bias Current

–6

µA

IOS

Input Offset Current

0.6

µA

CMRR

Common Mode Rejection Ratio

(Note 4)

PSRR

Power Supply Rejection Ratio

(Note 5)

Voltage Gain

(Note 6)

∞

VOH

Output High Voltage

ISOURCE = 4mA, VIN = VTRIP+ + 10mV

VCC – 0.4

VOL

Output Low Voltage

ISINK = 10mA, VIN = VTRIP– – 10mV

0.4

ICC

Supply Current (Per Comparator)

VCC = 5V

VCC = 3V

3.5

tPD20

Propagation Delay

VOVERDRIVE = 20mV (Note 7)

4.5

6.5

8.0

tPD5

Propagation Delay

VOVERDRIVE = 5mV (Notes 7, 8)

∆tPD

Differential Propagation Delay

(Note 9) Between Channels

0.3

1.0

tSKEW

Propagation Delay Skew

(Note 10) Between tPD

+/tPD–

0.5

1.5

Output Rise Time

10% to 90%

2.5

Output Fall Time

90% to 10%

2.2

tJITTER

Output Timing Jitter

VIN = 1.2VP-P (6dBm), ZIN = 50Ω

tPD+

psRMS

VCM = 2V, f = 20MHz

tPD

–

psRMS

fMAX

Maximum Toggle Frequency

VOVERDRIVE = 50mV, VCC = 3V

70.0

MHz

VOVERDRIVE = 50mV, VCC = 5V

62.5

MHz

Note 1: Absolute Maximum Ratings are those values beyond which the

life of a device may be impaired.

Note 2: If one input is within these common mode limits, the other

input can go outside the common mode limits and the output will be

valid.

Note 3: The LT1720/LT1721 comparators include internal hysteresis.

The trip points are the input voltage needed to change the output state

in each direction. The offset voltage is defined as the average of VTRIP+

and VTRIP–, while the hysteresis voltage is the difference of these two.

Note 4: The common mode rejection ratio is measured with VCC = 5V

and is defined as the change in offset voltage measured from VCM =

– 0.1V to VCM = 3.8V, divided by 3.9V.

Note 5: The power supply rejection ratio is measured with VCM = 1V

and is defined as the change in offset voltage measured from VCC =

2.7V to VCC = 6V, divided by 3.3V.

Note 6: Because of internal hysteresis, there is no small-signal region

in which to measure gain. Proper operation of internal circuity is

ensured by measuring VOH and VOL with only 10mV of overdrive.

Note 7: Propagation delay measurements made with 100mV steps.

Overdrive is measured relative to VTRIP±.

Note 8: tPD cannot be measured in automatic handling equipment with

low values of overdrive. The LT1720/LT1721 are 100% tested with a

100mV step and 20mV overdrive. Correlation tests have shown that

tPD limits can be guaranteed with this test, if additional DC tests are

performed to guarantee that all internal bias conditions are correct.

Note 9: Differential propagation delay is defined as the larger of the

two:

∆tPDLH = tPDLH(MAX) – tPDLH(MIN)

∆tPDHL = tPDHL(MAX) – tPDHL(MIN)

where (MAX) and (MIN) denote the maximum and minimum values of

a given measurement across the different comparator channels.

Note 10: Propagation Delay Skew is defined as:

tSKEW = |tPDLH – tPDHL|

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