Datasheet

or
R
EXT
=
-11 k:
35V
ISC
ISC =
35V
R
EXT
+ 11 k:
or
R
EXT
=
-11 k:
50[GHz · :]
GBW - 11 kHz
GBW = 11 kHz +
50[GHz · :]
R
EXT
+ 11 k:
R
EXT
= 40 x
110 mV
PSI ± 1 PA
-11 k:
PSI = 1 PA + 40
x
+
R
EXT
11k
110 mV
I
SEL
+
-
-
+
VOUT
LPV531
V
CONTROL
R
EXT2
R
EXT1
DAC
IN
LPV531
www.ti.com SNOSAK5B –MARCH 2006–REVISED MARCH 2013
Figure 38. DAC Controlled Power Mode Configurations
The output of the resistive voltage divider should have an impedance that is small compared to the value of R
INT
to allow a linear control of the power level. Therefore, R
EXT2
needs to have a value in the order of R
INT
/10 and
R
EXT1
= 125 mV * R
EXT2
/V
CONTROL,MAX
. For 1 µA power mode operation, these resistor values will divide the
maximum voltage of V
CONTROL
to 125 mV.
DETERMINING THE R
EXT
VALUES AND I
SEL
LEVELS
To determine the value of R
EXT
that is needed for a certain supply current or bandwidth, the following equations
can be used:
(1)
or
(2)
(3)
For the power modes characterized in this datasheet, these formulas lead to the values in Table 1. These values
deviate slightly from the typical values presented in the Electrical Characteristics tables. The values in Table 1
are calculated using approximated linear equations while the values in the Electrical Characteristics tables are
the result of characterization measurement procedures.
Table 1. Values for Characterized Power Modes
R
EXT
I
SEL
Supply Current Gain Bandwidth Product
1Ω 9 µA 400 µA 4.6 MHz
100 kΩ 0.9 µA 40 µA 460 kHz
1 MΩ 99 nA 5.3 µA 60 kHz
To calculate the R
EXT
which will allow the LPV531 to deliver a minimum output current at all times and over all
temperatures, use the following equations:
(4)
If the output has to be kept at V
+
/2 for a known load resistance, the required R
EXT
can be calculated with the
following equations:
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