low for a maximum of 6µs, during which time SCLK
should remain low for best noise performance. An inter-
nal register stores data when the conversion is in
progress. SCLK clocks the data out of the internal stor-
age register at any time after the conversion is com-
plete.
The MSB of the conversion is available at DOUT when
SSTRB goes high. The subsequent 15 falling edges on
SCLK shift the remaining bits out of the internal storage
register (Figure 4). CS does not need to be held low
once a conversion is started.
When internal clock mode is selected, SSTRB does not
go into a high-impedance state when CS goes high.
Figure 5 shows the SSTRB timing in internal clock
mode. In internal clock mode, data can be shifted in to
the MAX1132/MAX1133 at clock rates up to 4.8MHz,
provided that the minimum acquisition time, t
ACQ
, is
kept above 1.14µs in bipolar mode and 1.82µs in
unipolar mode. Data can be clocked out at 8MHz.
Output Data
The output data format is straight binary for unipolar
conversions and two’s complement in bipolar mode. In
both modes the MSB is shifted out of the MAX1132/
MAX1133 first.
Data Framing
The falling edge of CS does NOT start a conversion on
the MAX1132/MAX1133. The first logic high clocked into
DIN is interpreted as a start bit and defines the first bit of
the Control Byte. A conversion starts on the falling edge
of SCLK, after the seventh bit of the Control Byte (the P1
bit) is clocked into DIN. The start bit is defined as:
The first high bit clocked into DIN with CS low any-
time the converter is idle, e.g., after AV
DD
is
applied, or as the first high bit clocked into DIN
after CS is pulsed high, then low.
OR
If a falling edge on CS forces a start bit before the
conversion or calibration is complete, then the
current operation will be terminated and a new
one started.
Applications Information
Power-On Reset
When power is first applied to the MAX1132/MAX1133
or if RST is pulsed low, the internal calibration registers
are set to their default values. The user-programmable
registers (P0, P1, and P2) are low, and the device is
configured for bipolar mode with internal clocking.
Calibration
To compensate the MAX1132/MAX1133 for temperature
drift and other variations, they should be periodically
calibrated. After any change in ambient temperature
more than 10°C the device should be recalibrated. A
100mV change in supply voltage or any change in the
reference voltage should be followed by a calibration.
Calibration corrects for errors in gain, offset, integral
nonlinearity, and differential nonlinearity. The MAX1132/
MAX1133 should be calibrated after power-up or the
assertion of reset. Make sure the power supplies and
the reference voltage have fully settled prior to initiating
the calibration sequence.
Initiate calibration by setting M1 = 0 and M0 = 1 in the
Control-Byte. In internal clock mode, SSTRB goes low at
MAX1132/MAX1133
16-Bit ADC, 200ksps, 5V Single-Supply
with Reference
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