6

LTC1392

TEST CIRCUITS

WAVEFORM 1

(SEE NOTE 1)

2.0V

90%

10%

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

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

transfer is initiated by a falling chip select (CS) signal. After

the falling CS is recognized, an 80

µs 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

1.4V

3k

100pF

TEST POINT

LTC1392 • TC02

CLK

LTC1392 • TC03

3k

100pF

TEST POINT

LTC1392 • TC05

1392 TC04