Single/Dual/Quad, Ultra-High-Speed, +3V/+5V,

Beyond-the-Rails Comparators

10

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Output Stage Circuitry

The MAX961–MAX964/MAX997/MAX999 contain a cur-

rent-driven output stage, as shown in Figure 4. During an

the output pin. The output source or sink current is high

during the transition, creating a rapid slew rate. Once the

current decreases to a small value, capable of maintain-

current conserves power after an output transition has

occurred.

One consequence of a current-driven output stage is a

linear dependence between the slew rate and the load

capacitance. A heavy capacitive load slows down the

voltage output transition.

Shutdown Mode

When SHDN is high, the MAX961/MAX963/MAX964/

MAX997 shut down. When shut down, the supply cur-

rent drops to 270µA per comparator, and the outputs

become high impedance. SHDN has a high input

impedance. Connect SHDN to GND for normal opera-

tion. Exit shutdown with LE low; otherwise, the output is

indeterminate.

__________Applications Information

Circuit Layout and Bypassing

The MAX961–MAX964/MAX997/MAX999’s high band-

width requires a high-speed layout. Follow these layout

guidelines:

1) Use a PCB with a good, unbroken, low-inductance

ground plane.

2) Place a decoupling capacitor (a 0.1µF ceramic sur-

face-mount capacitor is a good choice) as close to

3) On the inputs and outputs, keep lead lengths short

to avoid unwanted parasitic feedback around the

comparators. Keep inputs away from outputs. Keep

impedance between the inputs low.

4) Solder the device directly to the printed circuit board

rather than using a socket.

5) Refer to Figure 5 for a recommended circuit layout.

6) For slow-moving input signals, take care to prevent

parasitic feedback. A small capacitor (1000pF or

less) placed between the inputs can help eliminate

oscillations in the transition region. This capacitor

source impedance is low.

Figure 4. Output Stage Circuitry

MAX961-MAX964

MAX997

MAX999

Q, Q

GND

Figure 5. MAX961 PCB Layout