R

=

BIAS

= 0.9 MW

V

BATTMIN

I

BIAS

=

1.8 V

2

A

m

R =

2

-

V

THRS

V

BATT

1

R

1

1

( ) - 1

R

1

=

-

2 V

1.2 V

420 kW

´

1

420 kW

1

(

)

-

1

20 MW

= 650 kW

R = R

1

F

= 20 MW

V

HYST

V

BATT

= 420 kW

50 mV

2.4 V

R =

F

V

REF

1000 (I

BMAX)

=

1.2 V

1000 (50 pA)

= 24 M

20 M

W

W

»

REF1112

TLV369

+IN

OUT

-IN

V

STATUS

V

BATT

V

REF

R

1

R

2

R

BIAS

I

BIAS

R

F

+

Copyright © 2016, Texas Instruments Incorporated

14

TLV369, TLV2369

SBOS757 – MAY 2016

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Copyright © 2016, Texas Instruments Incorporated

8.3 System Examples

8.3.1 Battery Monitoring

The low operating voltage and quiescent current of the TLV369 series make the family an excellent choice for

battery-monitoring applications, as shown in Figure 17.

Figure 17. Battery Monitor

In this circuit, VSTATUS is high as long as the battery voltage remains above 2 V. A low-power reference is used to

set the trip point. Resistor values are selected as follows:

1. Selecting RF: Select RF such that the current through RF is approximately 1000 times larger than the

maximum bias current over temperature, as given by Equation 4:

(4)

2. Choose the hysteresis voltage, VHYST. For battery-monitoring applications, 50 mV is adequate.

3. Calculate R1 as calculated by Equation 5:

(5)

4. Select a threshold voltage for VIN rising (VTHRS) = 2.0 V.

5. Calculate R2 as given by Equation 6:

(6)

6. Calculate RBIAS: The minimum supply voltage for this circuit is 1.8 V. The REF1112 has a current

requirement of 1.2

μA (max). Providing the REF1112 with 2 μA of supply current assures proper operation.

Therefore, RBIAS is as given by Equation 7.

(7)