MAX1134 Datasheet, PDF (8/18 Pages) Maxim Integrated Products – 16-Bit ADCs, 150ksps, 3.3V Single Supply

16-Bit ADCs, 150ksps, 3.3V Single Supply
Detailed Description
The MAX1134/MAX1135 ADCs use a successive-
approximation technique and input track/hold (T/H) cir-
cuitry to convert an analog signal to a 16-bit digital
output. The MAX1134/MAX1135 easily interface to
microprocessors (µPs). The data bits can be read either
during the conversion in external clock mode or after the
conversion in internal clock mode.
BIPOLAR
S1
VOLTAGE
REFERENCE
R1
2.5kΩ
R2
AIN
UNIPOLAR
TRACK
S2
C_HOLD
32pF
T/H OUT
R3
HOLD _TRACK
HOLD
S3
S1 = BIPOLAR/UNIPOLAR
S2, S3 = T/H SWITCH
R2 = 7.6kΩ (MAX1134)
OR 2.5kΩ (MAX1135)
R3 = 3.9kΩ (MAX1134)
OR INFINITY (MAX1135)
Figure 1. Equivalent Input Circuit
Table 1. Control Byte Format
In addition to a 16-bit ADC, the MAX1134/MAX1135
include an input scaler, an internal digital microcontroller,
calibration circuitry, and an internal clock generator.
The input scaler for the MAX1134 enables conversion
of input signals ranging from 0 to +6V (unipolar input)
or ±6V (bipolar input). The MAX1135 accepts 0 to
+2.048V (unipolar input) or ±2.048V (bipolar input). The
input range is software selectable.
Calibration
To minimize linearity, offset, and gain errors, the
MAX1134/MAX1135 have on-demand software calibra-
tion. Initiate calibration by writing a control byte with bit
M1 = 0 and bit M0 = 1 (Table 1). Select internal or exter-
nal clock for calibration by setting the INT/EXT bit in the
control byte. Calibrate the MAX1134/MAX1135 with the
same clock mode used for performing conversions.
Offsets resulting from synchronous noise (such as the
conversion clock) are canceled by the MAX1134/
MAX1135’s calibration circuitry. However, because the
magnitude of the offset produced by a synchronous
signal depends on the signal’s shape, recalibration
may be appropriate if the shape or relative timing of the
clock, or other digital signals change, as may occur if
more than one clock signal or frequency is used.
Input Scaler
The MAX1134/MAX1135 have an input scaler, which
allows conversion of true bipolar input voltages while
operating from a single 3.3V supply. The input scaler
attenuates and shifts the input as necessary to map the
external input range to the input range of the internal
ADC. The MAX1134 analog input range is 0 to +6V
(unipolar) or ±6V (bipolar). The MAX1135 analog input
BIT
7 (MSB)
NAME
START
DESCRIPTION
The first logic 1 bit after CS goes low defines the beginning of the control byte.
6
5
4
3
2
1
0 (LSB)
UNI/BIP
INT/EXT
M1
M0
P2
P1
P0
1 = unipolar, 0 = bipolar. Selects unipolar or bipolar conversion mode. In unipolar mode, analog input
signals from 0 to +6V (MAX1134) or 0 to +V_REF (MAX1135) can be converted. In bipolar mode, analog
input signals from -6V to +6V (MAX1134) or -V_REF to +V_REF (MAX1135) can be converted.
Selects the internal or external conversion clock. 1 = internal, 0 = external.
M1
M0
Mode
0
0
24 external clocks per conversion (short acquisition mode)
0
1
Start calibration: starts internal calibration
1
0
Software power-down mode
1
1
32 external clocks per conversion (long acquisition mode)
These 3 bits are stored in a port register and output to pins P2, P1, and P0 for use in addressing a mux
or PGA. These 3 bits are updated in the port register simultaneously when a new control byte is written.
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