Datasheet

R
INT
V
INT
PROGRAMMABLE
BIAS GENERATOR
I
PROG
LOW POWER
BIAS GERERATOR
I
REF
I
STDB
V
CC
V
EE
OUT
+IN
-IN
BIAS
I
SEL
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 I
SEL
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 (I
REF
) to the amplifier core. The programmable bias generator generates a 110 mV reference voltage
(V
INT
). This reference voltage is converted into a programmable reference current (I
PROG
) through the internal
resistor (R
INT
) and the external resistor (R
EXT
) connected to the I
SEL
pin. Internally, I
PROG
is added to the output
current from the low power bias generator (I
STDB
). When the I
SEL
pin is left floating, I
PROG
equals zero and the I
REF
equals I
STDB
. The value of I
STDB
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 (R
EXT
) from the I
SEL
pin to V
−
. Together with the internal circuitry, R
EXT
will determine the
current drawn from the I
SEL
pin. Internally the I
SEL
pin is connected to an 11 kΩ internal series resistor (R
INT
)
which is biased at V
INT
= 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 R
EXT
can
be calculated using the equations in the section “DETERMINING THE I
SEL
LEVELS”.
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