Datasheet

External Circuitry for Additional V
BUS
Input
N-channelMOSFETs
dualpairsuchasVishay
Si1034
Shunt
R
SHUNT
P-channelMOSFETs
dualpairssuchasVishay
Si3991DV
ControlFET
FromHot
Swap
Controller
10kW10kW
Supply
Voltage
Critical
DAC+
Critical
DAC -
´
CMP
CMP
Filter
Watchdog
PowerRegister
CurrentRegister
I C
2
Interface
VoltageRegister
ConvertGND
ADC
GPIO
INA209
CriticalOutput
OverlimitOutput
WarningOutput
Alert
Data(SDA)
CLK(SCL)
V
IN+
V
IN-
V
S
INA209
SBOS403B JUNE 2007 REVISED MARCH 2009 .........................................................................................................................................................
www.ti.com
through the resistance of any external switching
method used. The easiest way to avoid these errors
The INA209 GPIO can be used to control an external
is by reducing this resistance to a minimum; select
circuit to switch the V
BUS
measurement to an
switching MOSFETs with the lowest possible R
DS(on)
alternate location. Switching is most often done to
values.
perform bus voltage measurements on the opposite
side of a MOSFET switch in series with the shunt The circuit shown in Figure 24 uses MOSFET pairs to
resistor. reduce package count. Back-to-back MOSFETs must
be used in each leg because of the built-in back
Consideration must be given to the typical 20 µ A input
diodes from source-to-drain. In this circuit, the normal
current of each INA209 input, along with the 320k
connection for V
IN
is at the shunt, with the optional
impedance present at the V
IN
input where the bus
voltage measurement at the output of the control
voltage is measured. These effects can create errors
FET.
Figure 24. External Circuitry for Additional V
BUS
Input
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