MAX1036_09 Datasheet, PDF (11/23 Pages) Maxim Integrated Products – 2.7V to 3.6V and 4.5V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs

2.7V to 3.6V and 4.5V to 5.5V, Low-Power,
4-/12-Channel 2-Wire Serial 8-Bit ADCs
Table 1. Setup Byte Format
BIT 7
(MSB)
REG
BIT 6
SEL2
BIT 5
SEL1
BIT 4
SEL0
BIT 3
CLK
BIT 2
BIP/UNI
BIT 1
RST
BIT 0
(LSB)
X
BIT
NAME
DESCRIPTION
7
REG
Register bit. 1 = Setup Byte, 0 = Configuration Byte (Table 2).
6
SEL2
5
SEL1
Three bits select the reference voltage and the state of AIN_/REF (Table 6). Default to 000 at
power-up.
4
SEL0
3
CLK
1 = External clock, 0 = Internal clock. Defaulted to zero at power-up.
2
BIP/UNI
1 = Bipolar, 0 = Unipolar. Defaulted to zero at power-up (see the Unipolar/Bipolar section).
1
RST
1 = No action, 0 = Resets the configuration register to default. Setup register remains
unchanged.
0
X
Don’t care, can be set to 1 or 0.
Single-Ended/Pseudo-Differential Input
The SGL/DIF bit of the configuration byte configures the
MAX1036–MAX1039 analog input circuitry for single-
ended or pseudo-differential inputs (Table 2). In single-
ended mode (SGL/DIF = 1), the digital conversion results
are the difference between the analog input selected by
CS[3:0] and GND (Table 3). In pseudo-differential mode
(SGL/DIF = 0), the digital conversion results are the differ-
ence between the ‘+’ and the ‘-’ analog inputs selected
by CS[3:0] (Table 4). The ‘-’ analog input signal must
remain stable within ±0.5LSB (±0.1LSB for best results)
with respect to GND during a conversion.
Unipolar/Bipolar
When operating in pseudo-differential mode, the BIP/
UNI bit of the setup byte (Table 1) selects unipolar or
bipolar operation. Unipolar mode sets the differential
analog input range from zero to V_REF. A negative differ-
ential analog input in unipolar mode causes the digital
output code to be zero. Selecting bipolar mode sets the
differential input range to ±V_REF/2, with respect to the
negative input. The digital output code is binary in
unipolar mode and two’s complement binary in bipolar
mode (see the Transfer Functions section).
In single-ended mode, the MAX1036–MAX1039 always
operate in unipolar mode regardless of the BIP/UNI
setting, and the analog inputs are internally referenced
to GND with a full-scale input range from zero to V_REF.
Digital Interface
The MAX1036–MAX1039 feature a 2-wire interface con-
sisting of a serial data line (SDA) and a serial clock line
(SCL). SDA and SCL facilitate bidirectional communica-
tion between the MAX1036–MAX1039 and the master
at rates up to 1.7MHz. The MAX1036–MAX1039 are
slaves that transmit and receive data. The master (typi-
cally a microcontroller) initiates data transfer on the bus
and generates SCL to permit that transfer.
SDA and SCL must be pulled high. This is typically
done with pullup resistors (500Ω or greater) (see
Typical Operating Circuit). Series resistors (R_S) are
optional. They protect the input architecture of the
MAX1036–MAX1039 from high-voltage spikes on the
bus lines and minimize crosstalk and undershoot of the
bus signals.
Bit Transfer
One data bit is transferred during each SCL clock
cycle. Nine clock cycles are required to transfer the
data in or out of the MAX1036–MAX1039. The data on
SDA must remain stable during the high period of the
SCL clock pulse. Changes in SDA while SCL is high are
control signals (see the START and STOP Conditions
section). Both SDA and SCL idle high when the bus is
not busy.
START and STOP Conditions
The master initiates a transmission with a START condi-
tion (S), a high-to-low transition on SDA with SCL high.
The master terminates a transmission with a STOP
condition (P), a low-to-high transition on SDA, while
______________________________________________________________________________________ 11