MAX188BEWP+T Maxim Integrated Products, MAX188BEWP+T Datasheet - Page 10

• Manufacturer Part Number: MAX188BEWP+T
• Description: IC ADC 12BIT SERIAL 20-SOIC
• Manufacturer: Maxim Integrated Products
• Type: Data Acquisition System (DAS)r

Specifications of MAX188BEWP+T

• Resolution (bits): 12 b
• Sampling Rate (per Second): 133k
• Data Interface: Serial
• Voltage Supply Source: Dual ±
• Voltage - Supply: ±5V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-SOIC (7.5mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

single-ended unipolar conversions on CH7 in external
clock mode without powering down between conver-
sions. In external clock mode, the SSTRB output pulses
high for one clock period before the most significant bit
of the 12-bit conversion result comes out of DOUT.
Varying the analog input to CH7 should alter the
sequence of bits from DOUT. A total of 15 clock cycles
is required per conversion. All transitions of the SSTRB
and DOUT outputs occur on the falling edge of SCLK.
A conversion is started on the MAX186/MAX188 by
clocking a control byte into DIN. Each rising edge on
SCLK, with CS low, clocks a bit from DIN into the
MAX186/MAX188’s internal shift register. After CS falls,
the first arriving logic “1” bit defines the MSB of the
control byte. Until this first “start” bit arrives, any num-
ber of logic “0” bits can be clocked into DIN with no
effect. Table 2 shows the control-byte format.
Low-Power, 8-Channel,
Serial 12-Bit ADCs
Table 2. Control-Byte Format
10
Bit 7
(MSB)
START
Bit
7(MSB)
6
5
4
3
2
1
0(LSB)
______________________________________________________________________________________
SEL2
Bit 6
Name
START
SEL2
SEL1
SEL0
UNI/BIP
PD1
PD0
SGL/DIF
How to Start a Conversion
SEL1
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.
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
1 = single ended, 0 = differential. Selects single-ended or differential conversions. In
single-ended mode, input signal voltages are referred to AGND. In differential mode,
the voltage difference between two channels is measured. See Tables 3 and 4.
Selects clock and power-down modes.
PD1
0
0
1
1
Bit 5
See Tables 3 and 4.
signal can range from -VREF/2 to +VREF/2.
PD0
0
1
0
1
Bit 4
SEL0
Mode
Full power-down (I
Fast power-down (I
Internal clock mode
External clock mode
The MAX186/MAX188 are fully compatible with
Microwire and SPI devices. For SPI, select the correct
clock polarity and sampling edge in the SPI control reg-
isters: set CPOL = 0 and CPHA = 0. Microwire and SPI
both 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
12-bit conversion result).
Make sure the CPU’s serial interface runs in master
mode so the CPU generates the serial clock. Choose a
clock frequency from 100kHz to 2MHz.
1) Set up the control byte for external clock mode, call
UNI/BIP
Bit 3
it TB1. TB1 should be of the format: 1XXXXX11
Binary, where the Xs denote the particular channel
and conversion-mode selected.
Q
Q
= 2µA)
= 30µA)
SGL/DIF
Example: Simple Software Interface
Bit 2
Bit 1
PD1
(LSB)
Bit 0
PD0