Datasheet

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_
+
_
+
R1
R2
Reference
Voltage of
1.207 V
RSTSENSE
RESET
LSENSE
HSENSE
V
DD
GND
TPS3806
Detailed Description
Operation
Programming the Threshold Voltage Levels
V
(LSENSE)
 V
ref

R1  R2  R3
R2  R3

(1)
V
(HSENSE)
 V
ref

R1  R2  R3
R3

(2)
TPS3806J20
TPS3806I33
SLVS393A – JULY 2001 – REVISED NOVEMBER 2004
FUNCTIONAL BLOCK DIAGRAM
The TPS3806 is used for monitoring battery voltage and asserting RESET when a battery gets discharged below
a certain threshold voltage. The battery voltage is monitored by a comparator via an external resistor divider.
When the voltage at the LSENSE input drops below the internal reference voltage the RSTSENSE output pulls
low. The output remains low until the battery is replaced, or recharged above a second higher trip-point, set at
HSENSE. A second voltage can be monitored at V
DD
. The independent RESET output pulls low when the
voltage at V
DD
drops below the fixed threshold voltage. Because the TPS3806 outputs are open-drain MOSFETs,
most applications may require a pull-up resistor.
The low-voltage threshold at LSENSE is calculated according to Equation 1 :
where V
ref
= 1.207 V
The high-voltage threshold at HSENSE is calculated as shown in Equation 2 :
where V
ref
= 1.207 V
To minimize battery current draw it is recommended to use 1-M Ω as the total resistor value R
(tot)
, with
R
(tot)
= R1 + R2 + R3.
5