MAX148 View Datasheet(PDF) - Maxim Integrated
Part Name
Description
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MAX148 Datasheet PDF : 23 Pages
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+2.7V to +5.25V, Low-Power, 8-Channel,
Serial 10-Bit ADCs
Table 1. Control-Byte Format
BIT 7
(MSB)
START
BIT 6
SEL2
BIT 5
SEL1
BIT 4
SEL0
BIT 3
UNI/BIP
BIT 2
SGL//DIF
BIT 1
PD1
BIT 0
(LSB)
PD0
BIT
7(MSB)
6
5
4
3
2
1
0(LSB)
NAME
START
SEL2
SEL1
SEL0
UNI/BIP
SGL/DIF
PD1
PD0
DESCRIPTION
The first logic “1” bit after CS goes low defines the beginning of the control byte.
These three bits select which of the eight channels are used for the conversion (Tables 2 and 3)
1 = unipolar, 0 = bipolar. Selects unipolar or bipolar conversion mode. In unipolar mode, an
analog input signal from 0 to VREF can be converted; in bipolar mode, the signal can range from
-VREF/2 to +VREF/2.
1 = single ended, 0 = differential. Selects single-ended or differential conversions. In single-
ended mode, input signal voltages are referred to COM. In differential mode, the voltage
difference between two channels is measured (Tables 2 and 3).
Selects clock and power-down modes.
PD1
PD0
Mode
0
0
Full power-down
0
1
Fast power-down (MAX149 only)
1
0
Internal clock mode
1
1
External clock mode
Table 2. Channel Selection in Single-Ended Mode (SGL/DIF = 1)
SEL2
0
1
0
1
0
1
0
1
SEL1
0
0
0
0
1
1
1
1
SEL0
0
0
1
1
0
0
1
1
CH0
+
CH1
+
CH2
+
CH3
+
CH4
+
CH5
+
CH6
+
CH7
+
COM
-
-
-
-
-
-
-
-
How to Start a Conversion
Start a conversion by clocking a control byte into DIN.
With CS low, each rising edge on SCLK clocks a bit from
DIN into the MAX148/MAX149’s internal shift register.
After CS falls, the first arriving logic “1” bit defines the
control byte’s MSB. Until this first “start” bit arrives, any
number of logic “0” bits can be clocked into DIN with no
effect. Table 1 shows the control-byte format.
The MAX148/MAX149 are compatible with SPI/QSPI and
MICROWIRE devices. For SPI, select the correct clock
polarity and sampling edge in the SPI control 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, the simplest
software interface requires only three 8-bit transfers to
perform a conversion (one 8-bit transfer to configure
the ADC, and two more 8-bit transfers to clock out the
conversion result). See Figure 20 for MAX148/ MAX149
QSPI connections.
10
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