MAX912CSE(2003) データシートの表示（PDF） - Maxim Integrated

部品番号

コンポーネント説明

メーカー

MAX912CSE
(Rev.:2003)

Single/Dual, Ultra-Fast, Low-Power Precision TTL Comparators

Maxim Integrated 

Single/Dual, Ultra-Fast, Low-Power

Precision TTL Comparators

Detailed Description

The MAX912 (dual) and MAX913 (single) high-speed

comparators have a unique design that prevents oscil-

lation when the comparator is in its linear region. No

minimum input slew rate is required.

Many high-speed comparators oscillate in the linear

region, as shown in the Typical Operating Characteris-

tics’ industry-standard 686 response graph. One way

to overcome this oscillation is to sample the output after

it has passed through the unstable region. Another

practical solution is to add hysteresis. Either solution

results in a loss of resolution and bandwidth.

Because the MAX912/MAX913 do not need hysteresis,

they offer high resolution to all signals—including low-

frequency signals.

The MAX912/MAX913 provide a TTL-compatible latch

function that holds the comparator output state (Figure 1).

As long as Latch Enable (LE) is high or floating, the input

signal has no effect on the output state. With LE low, the

outputs are controlled by the input differential voltage

and the latch is transparent.

Input Amplifier

A comparator can be thought of as having two sec-

tions; an input amplifier and a logic interface. The

MAX912/MAX913’s input amplifier is fully differential

with input offset voltage trimmed to below 2.0mV at

+25°C. Input common-mode range extends from

200mV below the negative supply rail to 1.5V below

the positive power supply. The total common-mode

range is 8.7V when operating from ±5VDC supplies.

The MAX912/MAX913’s amplifier has no built-in hys-

teresis. For highest accuracy, do not add hysteresis.

Figure 2 shows how hysteresis degrades resolution.

Resolution

A comparator’s ability to resolve small signal differ-

ences—its resolution—is affected by various factors.

As with most amplifiers, the most significant factors are

the input offset voltage (VOS) and the common-mode

and power-supply rejection ratios (CMRR, PSRR). If

source impedance is high, input offset current can be

significant. If source impedance is unbalanced, the

input bias current can introduce another error.

For high-speed comparators, an additional factor in

resolution is the comparator’s stability in its linear

region. Many high-speed comparators are useless in

their linear region because they oscillate. This makes

the differential input voltage region around 0V unus-

able, as does a high VOS. Hysteresis does not cure the

problem, but acts to keep the input away from its linear

range (Figure 2).

The MAX912/MAX913 do not oscillate in the linear

region, which greatly enhances the comparator’s reso-

lution.

VIN

(DIFFERENTIAL)

tSU

tH

LATCH

ENABLE (LE)

tPD+

tLPD

Q

∆tPD

Q

tPD-

Figure 1. Timing Diagram

_______________________________________________________________________________________ 7

Share Link: