LMC6582 datasheet(11/19 Pages) NSC

11 / 19 page

3.0 Low Voltage Operation (Continued)

Battery Type

Nominal Voltage

End of Discharge

Voltage

NiMH

1.2V

NiCd

1.2V

Lead-Acid

1.8V

Silver Oxide

1.6V

1.3V

Carbon-Zinc

1.5V

1.1V

Lithium

2.6V–3.6V

1.7V–2.4V

At V

= 2.2V, the LMC6582/4 has a rail-to-rail input

common-mode voltage range.

Figure 4 shows an input volt-

age extending to both supplies and the resulting output.

The amplifier is operational at V

S = 1.8V, with guaranteed in-

put common-mode voltage range, output swing, and CMRR

specs.

Figure 5 shows the response of the LMC6582/4 at V

= 1.8V.

Figure 6 shows an input voltage exceeding both supplies

with no resulting phase inversion on the output.

4.0 Capacitive Load Tolerance

The LMC6582/4 can typically drive a 100 pF load with V

S =

10V at unity gain without oscillating. The unity gain follower

is the most sensitive configuration to capacitive load. Direct

capacitive loading reduces the phase margin of op-amps.

The combination of the op-amp’s output impedance and the

capacitive load induces phase lag. This results in either an

underdamped pulse response or oscillation.

Capacitive load compensation can be accomplished using

resistive isolation as shown in

Figure 7. If there is a resistive

component of the load in parallel to the capacitive compo-

nent, the isolation resistor and the resistive load create a

voltage divider at the output. This introduces a DC error at

the output.

Figure 8 displays the pulse response of the LMC6582 circuit

Figure 7.

DS012041-6

FIGURE 4. The Input Common-Mode Voltage

Range Extends to Both Supplies at V

S = 2.2V

DS012041-7

FIGURE 5. Response of the LMC6582/4

at V

S = 1.8V

DS012041-8

FIGURE 6. An Input Voltage Signal Exceeds

LMC6582/4 Power Supply Voltages of

S = 1.8V with No Output Phase Inversion

DS012041-9

FIGURE 7. Resistive Isolation of a 350 pF Capacitive

Load

DS012041-10

FIGURE 8. Pulse Response of the

LMC6582 Circuit in

Figure 7

LMC6582 Datasheet(PDF) 11 Page - National Semiconductor (TI)

LMC6582 Datasheet(HTML) 11 Page - National Semiconductor (TI)

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Datasheet Download

Link URL