Datasheet

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SLVS296 − JUNE 2000
6
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
detailed description (continued)
low-battery detector (TPS60210 and TPS60212)
The low-battery comparator trips at 1.18 V ±5% when the voltage on pin LBI ramps down. The voltage V
(TRIP)
at which the low-battery warning is issued can be adjusted with a resistive divider as shown in Figure 2. The
sum of resistors R1 and R2 is recommended to be in the 100-kΩ to 1-MΩ range.
LBO is an open drain output. An external pullup resistor to OUT, or any other voltage rail in the appropriate range,
in the 100-kΩ to 1-MΩ range is recommended. During start-up, the LBO output signal is invalid for the first
500 µs. LBO is high impedance when the device is programmed into snooze mode.
If the low battery function is not used, connect LBI to ground and leave LBO unconnected. When the device is
programmed into snooze mode (SNOOZE = LOW), the low-battery detector is disabled.
V
(TRIP)
+ 1.18 V
ǒ
1 )
R1
R2
Ǔ
_
+
+
−
V
REF
V
BAT
IN
R1
LBI
R2
LBO
R3
V
O
Figure 2. Programming of the Low-Battery Comparator Trip Voltage
A 100-nF ceramic capacitor should be connected in parallel to R2 if large line transients are expected. These
voltage drops may inadvertently trigger the low-battery comparator and produce a wrong low-battery warning
signal at the LBO pin.
Formulas to calculate the resistive divider for low-battery detection, with V
LBI
= 1.13 V to 1.23 V and the sum
of resistors R1 and R2 equal 1 MΩ:
R2 + 1MW
V
LBI
V
Bat
R1 + 1MW * R2
(1)
(2)
Formulas to calculate the minimum and maximum battery voltage:
V
Bat(min)
+ V
LBI(min)
R1
(min)
)
R2
(max)
R2
(max)
V
Bat(max)
+ V
LBI(max)
R1
(max)
) R2
(min)
R2
(min)
(3
)
(4
)