
23
LTC1286/LTC1298
A “Quick Look” Circuit for the LTC1286
Users can get a quick look at the function and timing of the
LT1286 by using the following simple circuit (Figure 13).
VREF is tied to VCC. VIN is applied to the +IN input and the
–IN input is tied to the ground. CS is driven at 1/16 the
clock rate by the 74C161 and DOUT outputs the data. The
output data from the DOUT pin can be viewed on an
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.
TYPICAL APPLICATIONS N
U
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
67
A from the 5V supply at fSMPL = 0.1kHz and 25A to
55
A from the battery. The 12-bits of resolution of the
LTC1286 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
an ADC input span of VREF to 2VREF (2.5V to 5V). The
resistor divider then scales the input voltage for 8V to 16V.
Figure 13. “Quick Look” Circuit for the LTC1286
CLR
CLK
A
B
C
D
P
GND
VCC
RC
QA
QB
QC
QD
T
LOAD
74C161
VIN
TO OSCILLOSCOPE
CLOCK IN 250kHz
LTC1286/98 F13
VCC
CLK
DOUT
LTC1286
+IN
–IN
GND
4.7
F
5V
VREF
CS
Figure 14. Scope Trace the LTC1286 “Quick Look” Circuit
Showing A/D Output 101010101010 (AAAHEX)
Figure 15. Micropower Battery Voltage Monitor
39k
5V
LT1004-2.5
200k
91k
3
BATTERY MONITOR
INPUT 8V TO 16V
1
F
0.1
F
CS
CLK
DOUT
LTC1286
LTC1286/98 F15
–IN
VCC
VREF
GND
+IN
MSB
(B11)
VERTICAL: 5V/DIV
HORIZONTAL: 10s/DIV
LSB
(B0)
NULL
BIT
LTC1286/98 F14
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.