MAX148 Maxim, MAX148 Datasheet - Page 10

• Manufacturer Part Number: MAX148
• Description: +2.7V to +5.25V / Low-Power / 8-Channel / Serial 10-Bit ADCs
• Manufacturer: Maxim

+2.7V to +5.25V, Low-Power, 8-Channel,
Serial 10-Bit ADCs
Table 1. Control-Byte Format
Table 2. Channel Selection in Single-Ended Mode
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 cor-
rect clock polarity and sampling edge in the SPI control
10
SEL2
BIT 7
(MSB)
START
BIT
7(MSB)
6
5
4
3
2
1
0(LSB)
0
1
0
1
0
1
0
1
______________________________________________________________________________________
SEL1
0
0
0
0
1
1
1
1
NAME
START
SEL2
SEL1
SEL0
UNI/BIP
SGL/DIF
PD1
PD0
BIT 6
SEL2
SEL0
How to Start a Conversion
0
0
1
1
0
0
1
1
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 0V 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
0
0
1
1
BIT 5
SEL1
CH0
+
PD0
0
1
0
1
CH1
+
BIT 4
SEL0
Mode
Full power-down
Fast power-down (MAX149 only)
Internal clock mode
External clock mode
CH2
+
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.
CH3
(SGL/D D I I F F = 1)
+
BIT 3
UNI/BIP
CH4
+
BIT 2
SGL/DIF
CH5
+
CH6
+
BIT 1
PD1
CH7
+
BIT 0
(LSB)
PD0
COM
–
–
–
–
–
–
–
–