6
LTC1392
TEST CIRCUITS
Voltage Waveforms for t
dis
D
OUT
WAVEFORM 1
(SEE NOTE 1)
2.0V
t
dis
90%
10%
D
OUT
WAVEFORM 2
(SEE NOTE 2)
CS
NOTE 1: WAVEFORM 1 IS FOR AN OUTPUT WITH INTERNAL CONDITIONS SUCH
THAT THE OUTPUT IS HIGH UNTIL DISABLED BY THE OUTPUT CONTROL.
NOTE 2: WAVEFORM 2 IS FOR AN OUTPUT WITH INTERNAL CONDITIONS SUCH
THAT THE OUTPUT IS LOW UNTIL DISABLED BY THE OUTPUT CONTROL.
LTC1392 • TC06
APPLICATIONS INFORMATION
WUU
U
DIGITAL CONSIDERATIONS
Serial Interface
The LTC1392 communicates with microprocessors and
other external circuitry via a synchronous, half-duplex,
3-wire serial interface (see Figure 1). The clock (CLK)
synchronizes the data transfer with each bit being trans-
mitted on the falling CLK edge and captured on the rising
CLK edge in both transmitting and receiving systems. The
input data is first received and then the A/D conversion
result is transmitted (half-duplex). Half-duplex operation
allows D
IN
and D
OUT
to be tied together allowing transmis-
sion over three wires: CS, CLK and DATA (D
IN
/D
OUT
). Data
transfer is initiated by a falling chip select (CS) signal. After
the falling CS is recognized, an 80µs delay is needed for
The LTC1392 is a micropower data acquisition system
designed to measure temperature, an on-chip power
supply voltage and a differential input voltage. The LTC1392
contains the following functional blocks:
1. On-chip temperature sensor
2. 10-bit successive approximation capacitive ADC
3. Bandgap reference
4. Analog multiplexer (MUX)
5. Sample-and-hold (S/H)
6. Synchronous, half-duplex serial interface
7. Control and timing logic
Load Circuit for t
dDO
, t
r
and t
f
D
OUT
1.4V
3k
100pF
TEST POINT
LTC1392 • TC02
Voltage Waveforms for D
OUT
Delay Time, t
dDO
CLK
D
OUT
V
IL
t
dDO
V
OL
V
OH
LTC1392 • TC03
Load Circuit for t
dis
and t
en
D
OUT
3k
100pF
TEST POINT
5V t
dis
WAVEFORM 2, t
en
t
dis
WAVEFORM 1
LTC1392 • TC05
Voltage Waveforms for D
OUT
Rise and Fall Times, t
r
and t
f
D
OUT
V
OL
V
OH
t
r
t
f
1392 TC04
