23

LTC1285/LTC1288

39k

2.7V

LT1004-1.2

220k

39k

3

Ω

BATTERY MONITOR

INPUT 8V TO 16V

1

µF

0.1

µF

CS

CLK

LTC1285

LTC1285/88 • F15

–IN

GND

+IN

Figure 15. Micropower Battery Voltage Monitor

Figure 13. “Quick Look” Circuit for the LTC1285

A “Quick Look” Circuit for the LTC1285

Users can get a quick look at the function and timing of the

LT1285 by using the following simple circuit (Figure 13).

–IN input is tied to the ground. CS is driven at 1/16 the

oscilloscope that is set up to trigger on the falling edge of

CS (Figure 14). Note the LSB data is partially clocked out

before CS goes high.

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

Micropower Battery Voltage Monitor

A common problem in battery systems is battery voltage

monitoring. This circuit monitors the 10 cell stack of NiCad

or NiMH batteries found in laptop computers. It draws only

40

62

µA from the battery. The 12-bits of resolution of the

LTC1285 are positioned over the desired range of 8V to

16V. This is easily accomplished by using the ADC’s

differential inputs. Tying the –input to the reference gives

resistor divider then scales the input voltage for 8V to 16V.

CLR

CLK

A

B

C

D

P

GND

RC

QA

QB

QC

QD

T

LOAD

74HC161

TO OSCILLOSCOPE

CLOCK IN 120kHz

LTC1285/88 • F13

CLK

LTC1285

+IN

–IN

GND

4.7

µF

2.7V

CS

MSB

(B11)

VERTICAL: 2V/DIV

HORIZONTAL: 20µs/DIV

LSB

(B0)

NULL

BIT

Figure 14. Scope Trace the LTC1285 “Quick Look” Circuit