Texas Instruments MSA025, Руководство пользователя

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IT
R1
V 1 0.405
R2
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EVM Setup and Operation
9 SLVUAY9 – November 2016
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TPS3808G01-Q1EVM (MSA025) Voltage Supervisor User Guide
4.2 Voltage Sense Input (SENSE)
The TPS3808G01-Q1 device has a SENSE pin that acts as the input for the voltage being supervised.
The EVM offers a two-pin header to monitor V
DD
through a voltage divider set to 1.8-V threshold voltage,
and also a test point if the user wants to connect an external voltage to be monitored. The SENSE pin
provides an input at which any system voltage can be monitored unless something is supplying the
SENSE pin, RST will be held low indefinitely. If the voltage on this pin drops below V
IT
, RESET is asserted
low. The SENSE pin is connected internally to a comparator at the negative input and the positive input is
connected to a 0.405-V reference. Using a voltage divider, use
Equation 1 to calculate V
IT
:
(1)
Resistor references can be seen in the EVM schematic to make sure the circuit is connected correctly.
The EVM comes with R1 = 100 k
Ω
, R2 = 22.6 k
Ω
, but both resistors can be desoldered from the board
and changed to meet the value the user requires. See data plots Figure 14 through Figure 16 .
Figure 14. RESET Asserted Due to SENSE Voltage
Falling Below V
IT
Figure 15. RESET Deasserting Due to SENSE Voltage
Rising Above V
IT
, C
T
is floating