LPV531 datasheet(13/27 Pages) TI

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RINT

VINT

PROGRAMMABLE

BIAS GENERATOR

IPROG

LOW POWER

BIAS GERERATOR

IREF

ISTDB

VCC

VEE

OUT

+IN

-IN

BIAS

ISEL

LPV531

www.ti.com

SNOSAK5B – MARCH 2006 – REVISED MARCH 2013

APPLICATION INFORMATION

The LPV531 is an extremely versatile operational amplifier because performance and power consumption can be

adjusted during operation. This provides a method to dynamically 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 ISEL

pin according to the application performance requirements.

CIRCUIT TOPOLOGY

As shown in Figure 35, the LPV531 contains two internal bias reference generators that deliver a reference

current (IREF) to the amplifier core. The programmable bias generator generates a 110 mV reference voltage

(VINT). This reference voltage is converted into a programmable reference current (IPROG) through the internal

resistor (RINT) and the external resistor (REXT) connected to the ISEL pin. Internally, IPROG is added to the output

current from the low power bias generator (ISTDB). When the ISEL pin is left floating, IPROG equals zero and the IREF

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 performance over the full temperature range is not ensured. The 1 µA

power mode operation is only recommended for applications with a temperature range between 0 and 70°C.

Figure 35. Simplified Schematic

POWER MODE CONTROL

To illustrate typical configurations three possible solutions to control the power mode(s) of the LPV531 will be

described.

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 (REXT) from the ISEL pin to V

−. Together with the internal circuitry, R

EXT will determine the

current drawn from the ISEL pin. Internally the ISEL pin is connected to an 11 kΩ internal series resistor (RINT)

which is biased at VINT = 110 mV. This set up is illustrated in Figure 36.

For a desired supply current, bandwidth, short circuit current, or load resistance, the required value of REXT can

be calculated using the equations in the section “DETERMINING THE ISEL LEVELS”.

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