MAX1270BCAI Datasheet, PDF (10/20 Pages) Maxim Integrated Products – Multirange, +5V, 8-Channel, Serial 12-Bit ADCs

Multirange, +5V, 8-Channel,
Serial 12-Bit ADCs
Input Bandwidth
The ADC’s input small-signal bandwidth depends on the
selected input range and varies from 1.5MHz to 5MHz
(see Electrical Characteristics). The MAX1270B/
MAX1271B maximum sampling rate is 110ksps (100ksps
for the MAX1270A/MAX1271A). By using undersampling
techniques, it is possible to digitize high-speed transient
events and measure periodic signals with bandwidths
exceeding the ADC’s sampling rate.
To avoid high-frequency signals being aliased into the
frequency band of interest, anti-aliasing filtering is rec-
ommended.
Input Range and Protection
The MAX1270/MAX1271 have software-selectable input
ranges. Each analog input channel can be indepen-
dently programmed to one of four ranges by setting the
appropriate control bits (RNG, BIP) in the control byte
(Table 1). The MAX1270 has selectable input ranges
extending to ±10V (±V_REF x 2.441), while the MAX1271
has selectable input ranges extending to ±V_REF. Figure
4 shows the equivalent input circuit.
A resistor network on each analog input provides
±16.5V fault protection for all channels. Whether or not
the channel is on, this circuit limits the current going
into or out of the pin to less than 2mA. This provides an
added layer of protection when momentary overvolt-
ages occur at the selected input channel, when a neg-
ative signal is applied to the input, and when the device
is configured for unipolar mode. The overvoltage pro-
tection is active even if the device is in power-down
mode or if V_DD = 0.
Digital Interface
The MAX1270/MAX1271 feature a serial interface that is
fully compatible with SPI/QSPI and MICROWIRE devices.
For SPI/QSPI, set CPOL = 0, CPHA = 0 in the SPI control
registers of the microcontroller. Figure 5 shows detailed
serial-interface timing information. See Table 1 for details
on programming the input control byte.
R1
CH_
BIPOLAR
S1
VOLTAGE
REFERENCE
R3
5.12kΩ
UNIPOLAR
OFF
S2
ON
C_HOLD
R2
S3
TRACK
HOLD
TRACK
S4
T/H
OUT
HOLD
S1 = BIPOLAR/UNIPOLAR SWITCH
S2 = INPUT MUX SWITCH
S3, S4 = T/H SWITCH
R1 = 12.5kΩ (MAX1270)
or 5.12kΩ (MAX1271)
R2 = 8.67kΩ (MAX1270)
or ∞ (MAX1271)
Figure 4. Equivalent Input Circuit
CS
SCLK
DIN
DOUT
t_CSS
t_CSH
t_DS
t_DH
t_DV
t_CH
t_CL
t_CSH
t_DO
t_TR
Figure 5. Detailed Serial-Interface Timing
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