MAX1220_10 Datasheet, PDF (33/43 Pages) Maxim Integrated Products – 12-Bit, Multichannel ADCs/DACs with FIFO, Temperature Sensing, and GPIO Ports

12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
Table 21. DAC Power-Up and Power-Down Commands
CONTROL
BITS
C3 C2 C1 C0
DATA BITS
DESCRIPTION
D3 D2 D1 D0
FUNCTION
1 1 1 1 ———————— 0 0 1 X
Power-Up
Power up individual DAC buffers indicated by data
in DAC0 through DAC7. A one indicates the DAC
output is connected and active. A zero does not
affect the DAC’s present state.
Power down individual DAC buffers indicated by
1
1
1
1
———————— 0
1
0
X
Power-Down 1
data in DAC0 through DAC7. A one indicates the
DAC output is disconnected and high impedance.
A zero does not affect the DAC’s present state.
Power down individual DAC buffers indicated by
data in DAC0 through DAC7. A one indicates the
1 1 1 1 — — — — — — — — 1 0 0 X Power-Down 2 DAC output is disconnected and pulled to AGND
with a 1kΩ resistor. A zero does not affect the DAC’s
present state.
Power down individual DAC buffers indicated by
data in DAC0 through DAC7. A one indicates the
1 1 1 1 — — — — — — — — 0 0 0 X Power-Down 3 DAC output is disconnected and pulled to AGND
with a 100kΩ resistor. A zero does not affect the
DAC’s present state.
Power down individual DAC buffers indicated by
data in DAC0 through DAC7. A one indicates the
1 1 1 1 — — — — — — — — 1 1 1 X Power-Down 4 DAC output is disconnected and pulled to REF1 with
a 100kΩ resistor. A zero does not affect the DAC’s
present state.
If CS goes high prior to completing 16 SCLK cycles, the
command is discarded. To initiate a new transfer, drive
CS low again.
For example, writing the DAC serial interface word 1111
0000 and 1111 0100 disconnects DAC outputs 4
through 7 and forces them to a high-impedance state.
DAC outputs 0 through 3 remain in their previous state.
Output-Data Format
Figures 6–9 illustrate the conversion timing for the
MAX1220/MAX1257/MAX1258. All 12-bit conversion
results are output in 2-byte format, MSB first, with four
leading zeros. Data appears on DOUT on the falling
edges of SCLK. Data is binary for unipolar mode and
two’s complement for bipolar mode and temperature
results. See Figures 3, 4, and 5 for input/output and
temperature-transfer functions.
ADC Transfer Functions
Figure 3 shows the unipolar transfer function for single-
ended or differential inputs. Figure 4 shows the bipolar
transfer function for differential inputs. Code transitions
occur halfway between successive-integer LSB values.
Output coding is binary, with 1 LSB = V_REF1 / 4096
(MAX1257) and 1 LSB = V_REF1 / 4096
(MAX1220/MAX1258) for unipolar and bipolar opera-
tion, and 1 LSB = +0.125°C for temperature measure-
ments. Bipolar true-differential results and
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