MAX1258 datasheet(33/43 Pages) MAXIM

33 / 43 page

12-Bit, Multichannel ADCs/DACs with FIFO,

Temperature Sensing, and GPIO Ports

______________________________________________________________________________________

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 = VREF1/4096

(MAX1257) and 1 LSB = VREF1/4096 (MAX1220/

MAX1258) for unipolar and bipolar operation, and 1

LSB = +0.125°C for temperature measurements.

Bipolar true-differential results and temperature-sensor

Table 21. DAC Power-Up and Power-Down Commands

CONTROL

BITS

DATA BITS

C3 C2 C1 C0

D3 D2 D1 D0

DESCRIPTION

FUNCTION

——— ————— 0

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.

——— ————— 0

Power-Down 1

Power down individual DAC buffers indicated by

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.

——— ————— 1

Power-Down 2

Power down individual DAC buffers indicated by

data in DAC0 through DAC7. A one indicates the

DAC output is disconnected and pulled to AGND

with a 1k

Ω resistor. A zero does not affect the DAC’s

present state.

——— ————— 0

Power-Down 3

Power down individual DAC buffers indicated by

data in DAC0 through DAC7. A one indicates the

DAC output is disconnected and pulled to AGND

with a 100k

Ω resistor. A zero does not affect the

DAC’s present state.

——— ————— 1

Power-Down 4

Power down individual DAC buffers indicated by

data in DAC0 through DAC7. A one indicates the

DAC output is disconnected and pulled to REF1 with

a 100k

Ω resistor. A zero does not affect the DAC’s

present state.

MAX1258 Datasheet(PDF) 33 Page - Maxim Integrated Products

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