First Bit (MSB) (LSB)
MAX1400
+5V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
16 ______________________________________________________________________________________
Special Function Register (Write-Only)
MDOUT: (Default = 0) Modulator Out Bit. MDOUT = 0
enables data readout on the DOUT pin, the normal con-
dition for the serial interface. MDOUT = 1 changes the
function of the DOUT and INT pins, providing raw, sin-
gle-bit modulator output instead of the normal serial-
data interface output. This allows custom filtering
directly on the modulator output, without going through
the on-chip digital filter. The INT pin provides a clock to
indicate when the modulator data at DOUT should be
sampled (falling edge of INT). Note that in this mode,
the on-chip digital filter continues to operate normally.
When MDOUT is returned to 0, valid data may be
accessed through the normal serial-interface read
operation.
FULLPD: (Default = 0) Complete Power-Down Bit.
FULLPD = 1 forces the part into a complete power-
down condition, which includes the clock oscillator. The
serial interface continues to operate. The part requires a
hardware reset to recover correctly from this condition.
Note: Changing the reserved bits in the special-func-
tion register from the default status of all 0s will select
one of the reserved modes and the part will not operate
as expected. This register is a write-only register.
However, in the event that this register is mistakenly
read, clock 24 bits of data out of the part to restore it to
the normal interface-idle state.
Transfer-Function Registers
The three transfer-function registers control the method
used to map the input voltage to the output codes. All
of the registers have the same format. The mapping of
control registers to associated channels depends on
the mode of operation and is affected by the state of
M1, M0, DIFF, and SCAN (Tables 8, 9, and 10).
Table 4. SCAN Mode Scanning
Sequences (SCAN = 1)
Table 5. Available Input Channels
(SCAN = 0)
Note: All other combinations reserved.
First Bit (MSB) (LSB)
AVAILABLE CHANNELSDIFF
1 CALOFF
1 CALGAIN01
10
0
0
AIN1–AIN6, AIN2–AIN6,
AIN3–AIN6, AIN4–AIN6
CALGAIN
1 AIN1–AIN2, AIN3–AIN4, AIN5–AIN600
01
0 CALOFF10
M0
0
M1
0
FUNCTION
0
RESERVED BITS
0
0
0
0
Name FULLPD
0
0
0
MDOUT
0
RESERVED BITS
Defaults
0
00
0
0
FUNCTION
0
U/B
0 0
G0 D1
00
D2
0
OFFSET CORRECTION
Name
D0
PGA GAIN CONTROL
G1
Defaults 00
D3G2
SEQUENCEDIFF
1
AIN1–AIN2, AIN3–AIN4,
AIN5–AIN6, CALOFF, CALGAIN
1
AIN1–AIN2, AIN3–AIN4,
AIN5–AIN6, CALOFF, CALGAIN
01
10
0
0
AIN1–AIN6, AIN2–AIN6, AIN3–AIN6,
AIN4–AIN6, AIN5–AIN6
AIN1–AIN6, AIN2–AIN6,
AIN3–AIN6, AIN4–AIN6,
AIN5–AIN6, CALOFF, CALGAIN
1 AIN1–AIN2, AIN3–AIN4, AIN5–AIN600
01
0
AIN1–AIN6, AIN2–AIN6, AIN3–AIN6,
AIN4–AIN6, AIN5–AIN6, CALOFF,
CALGAIN
10
M0
0
M1
0
Special Function Register (Write-Only)
Transfer-Function Register
