SN0402002DBVR datasheet(13/23 Pages) TI

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APPLICATION INFORMATION

R1 + R2

TRIP

IT(S)

* 1

(1)

TPS3106E09DBV

SENSE

GND

RSTVDD

RSTSENSE

2Cell

NiMH

ResetOutput

TPS3103xxx

TPS3106xxx

TPS3110xxx

SLVS363E – AUGUST 2001 – REVISED SEPTEMBER 2007

The TPS31xx family has a quiescent current in the 1-

μA to 2-μA range. When RESET is active, triggered by the

voltage monitored at VDD, the quiescent current increases to about 20 μA (see the Electrical Characteristics).

In some applications it is necessary to minimize the quiescent current even during the reset period. This is

especially true when the voltage of a battery is supervised and the RESET is used to shut down the system or

for an early warning. In this case the reset condition will last for a longer period of time. The current drawn from

the battery should almost be zero, especially when the battery is discharged.

For this kind of application, either the TPS3103 or TPS3106 is a good fit. To minimize current consumption,

select a version where the threshold voltage is lower than the voltage monitored at VDD. The TPS3106 has two

reset outputs. One output (RSTVDD) is triggered from the voltage monitored at VDD. The other output

(RSTSENSE) is triggered from the voltage monitored at SENSE. In the application shown in Figure 8, the

TPS3106E09 is used to monitor the input voltage of two NiCd or NiMH cells. The threshold voltage (V(TH) = 0.86

V) was chosen as low as possible to ensure that the supply voltage is always higher than the threshold voltage

at VDD. The voltage of the battery is monitored using the SENSE input. The voltage divider was calculated to

assert a reset using the RSTSENSE output at 2

× 0.8 V = 1.6 V.

where:

VTRIP is the voltage of the battery at which a reset is asserted and

VIT(S) is the threshold voltage at SENSE = 0.551 V.

R1 was chosen for a resistor current in the 1-

μA range.

With VTRIP = 1.6 V:

≡ 1.9

× R2

R1 = 820 k

Ω, R2 = 430 kΩ

Figure 8. Battery Monitoring with 3-

μA Supply Current for Device and Resistor Divider

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