LPV531 datasheet(12/17 Pages) NSC

12 / 17 page

Application Information

The LPV531 is an extremely versatile operational amplifier

because performance and power consumption can be ad-

justed during operation. This provides a method to dynami-

cally optimize the supply current, the bandwidth and the

output short circuit current in the application. The power level

can be set by the current drawn from the I

SEL pin according

to the application performance requirements.

CIRCUIT TOPOLOGY

As shown in Figure 1, the LPV531 contains two internal bias

reference generators that deliver a reference current (I

REF)

to the amplifier core. The programmable bias generator gen-

erates a 110 mV reference voltage (V

INT). This reference

voltage is converted into a programmable reference current

PROG) through the internal resistor (RINT) and the external

resistor (R

EXT) connected to the ISEL pin. Internally, IPROG is

added to the output current from the low power bias genera-

tor (I

STDB). When the ISEL pin is left floating, IPROG equals

zero and the I

REF equals ISTDB. The value of ISTDB is such

that in this mode the power supply current is below 1 µA. In

this 1 µA power mode, the LPV531 is functional but perfor-

mance over the full temperature range is not guaranteed.

The 1 µA power mode operation is only recommended for

applications with a temperature range between 0 and 70˚C.

POWER MODE CONTROL

To illustrate typical configurations three possible solutions to

control the power mode(s) of the LPV531 will be described.

1. Single Power Mode

If the application requires one single power mode for the

LPV531, then the easiest way to achieve this is to connect a

resistor (R

EXT) from the ISEL pin to V

−. Together with the

internal circuitry, R

EXT will determine the current drawn from

the I

SEL pin. Internally the ISEL pin is connected to an 11 k

Ω

internal

series

resistor

INT)

which

biased

INT = 110 mV. This set up is illustrated in Figure 2.

For a desired supply current, bandwidth, short circuit current,

or load resistance, the required value of R

EXT can be calcu-

lated using the equations in the section “DETERMINING

THE I

SEL LEVELS”.

20132337

FIGURE 1. Simplified Schematic

20132336

FIGURE 2. Single Power Mode

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