TPS60210, TPS60211, TPS60212, TPS60213

REGULATED 3.3 V, LOW RIPPLE CHARGE PUMP

WITH ULTRALOW OPERATING CURRENT

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-k

Ω 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-k

Ω 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

1

) R1

R2

_

+

+

−

VREF

VBAT

IN

R1

LBI

R2

LBO

R3

VO

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 VLBI = 1.13 V to 1.23 V and the sum

of resistors R1 and R2 equal 1 M

Ω:

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)