MAX1112 Maxim, MAX1112 Datasheet - Page 11

• Manufacturer Part Number: MAX1112
• Description: +5V / Low-Power / Multi-Channel / Serial 8-Bit ADCs
• Manufacturer: Maxim

in control bytes of $FF (hex), which trigger single-
ended, unipolar conversions on CH7 (MAX1112) or
CH3 (MAX1113) in external clock mode without power-
ing down between conversions. In external clock mode,
the SSTRB output pulses high for two clock periods
before the most significant bit (MSB) of the 8-bit con-
version result is shifted out of DOUT. Varying the ana-
log input alters the output code. A total of 10 clock
cycles is required per conversion. All transitions of the
SSTRB and DOUT outputs occur on SCLK’s falling
edge.
A conversion is started by clocking a control byte into
DIN. With CS low, each rising edge on SCLK clocks a bit
Table 4. Full-Scale and Zero-Scale Voltages
Figure 5. Quick-Look Circuit
*FULL-SCALE ANALOG INPUT, CONVERSION RESULT = $FF (HEX)
( ) ARE FOR THE MAX1113.
V
REFIN
Full Scale
ANALOG
+4.096V
INPUT
0V TO
+ COM
0.01µF
UNIPOLAR MODE
C1
1µF
______________________________________________________________________________________
How to Start a Conversion
REFIN
CH7 (CH3)
COM
REFOUT
MAX1112
MAX1113
Zero Scale
COM
SSTRB
+5V, Low-Power, Multi-Channel,
DGND
AGND
SHDN
SCLK
DOUT
V
DIN
CS
DD
0.1µF
N.C.
+V
Full Scale
+5V
Positive
+ COM
REFIN
from DIN into the MAX1112/MAX1113’s internal shift reg-
ister. After CS falls, the first arriving logic “1” bit at DIN
defines the MSB of the control byte. Until this first start bit
arrives, any number of logic “0” bits can be clocked into
DIN with no effect. Table 3 shows the control-byte format.
The MAX1112/MAX1113 are compatible with
MICROWIRE, SPI, and QSPI devices. For SPI, select the
correct clock polarity and sampling edge in the SPI con-
trol registers: set CPOL = 0 and CPHA = 0. MICROWIRE,
SPI, and QSPI all transmit a byte and receive a byte at the
same time. Using the Typical Operating Circuit (Figure 3),
the simplest software interface requires three 8-bit trans-
fers to perform a conversion (one 8-bit transfer to config-
ure the ADC, and two more 8-bit transfers to clock out the
/ 2
1µF
OSCILLATOR
500kHz
+5V
BIPOLAR MODE
Serial 8-Bit ADCs
Scale
COM
Zero
CH1
OSCILLOSCOPE
CH2
CH3
-V
Full Scale
Negative
+ COM
CH4
REFIN
/ 2
SCLK
SSTRB
DOUT*
11