OUT

LMT87

GND

OPTIONAL

BYPASS

CAPACITANCE

OUT

LMT87

GND

OPTIONAL

BYPASS

CAPACITANCE

LMT87, LMT87-Q1

www.ti.com

SNIS170A – MARCH 2013 – REVISED JUNE 2013

OUTPUT AND NOISE CONSIDERATIONS

A push-pull output gives the LMT87/LMT87-Q1 the ability to sink and source significant current. This is beneficial

when, for example, driving dynamic loads like an input stage on an analog-to-digital converter (ADC). In these

applications the source current is required to quickly charge the input capacitor of the ADC. See the

APPLICATION CIRCUITS section for more discussion of this topic. The LMT87/LMT87-Q1 is ideal for this and

other applications which require strong source or sink current.

measured

during

bench

tests.

Its

typical

attenuation

is

shown

in

the

TYPICAL

PERFORMANCE

CHARACTERISTICS section. A load capacitor on the output can help to filter noise.

For operation in very noisy environments, some bypass capacitance should be present on the supply within

approximately 5 centimeters of the LMT87/LMT87-Q1.

CAPACITIVE LOADS

The LMT87/LMT87-Q1 handles capacitive loading well. In an extremely noisy environment, or when driving a

switched sampling input on an ADC, it may be necessary to add some filtering to minimize noise coupling.

Without any precautions, the LMT87/LMT87-Q1 can drive a capacitive load less than or equal to 1100 pF as

shown in Figure 10. For capacitive loads greater than 1100 pF, a series resistor may be required on the output,

as shown in Figure 11.

Figure 10. LMT87 No Decoupling Required for Capacitive Loads Less than 1100 pF

Figure 11. LMT87 with Series Resistor for Capacitive Loading Greater than 1100 pF

1.1 nF to 99 nF

3 k

Ω

100 nF to 999 nF

1.5 k

Ω

1

μF

800

Ω

OUTPUT VOLTAGE SHIFT

The LMT87/LMT87-Q1 is very linear over temperature and supply voltage range. Due to the intrinsic behavior of

an NMOS/PMOS rail-to-rail buffer, a slight shift in the output can occur when the supply voltage is ramped over

specifications in the ELECTRICAL CHARACTERISTICS table already include this possible shift.

Copyright © 2013, Texas Instruments Incorporated

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Product Folder Links: LMT87 LMT87-Q1