Rainbow-electronics MAX5382 Manual de usuario descargar pdf (Pagina 9)

MAX5380/MAX5381/MAX5382

Low-Cost, Low-Power, 8-Bit DACs with

2-Wire Serial Interface in SOT23

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Power-On Reset

The MAX5380/MAX5381/MAX5382 have a power-on

reset circuit to set the DAC’s output to 0 when V

first applied or when V

dips below 1.7V (typ). This

ensures that unwanted DAC output voltages will not

occur immediately following a system startup, such as

after a loss of power. The output glitch at startup is typi-

cally less than 50mV.

Shutdown Mode

The MAX5380/MAX5381/MAX5382 include a software-

controlled shutdown mode that reduces the supply cur-

rent to <1µA. All internal circuitry is disabled, and an

internal 10kΩ resistor is placed from OUT to GND to

ensure 0V at OUT while in shutdown. The device enters

shutdown in less than 5µs and exits shutdown in less

than 50µs.

Digital Section

Serial Interface

The MAX5380/MAX5381/MAX5382 use a simple 2-wire

serial interface requiring only two I/O lines (2-wire bus)

of a standard microprocessor (µP) port. Figure 3 shows

the timing diagram for signals on the 2-wire bus.

The two bus lines (SDA and SCL) must be high when

the bus is not in use. The MAX5380/MAX5381/

MAX5382 are receive-only devices (slaves) and must

be controlled by a bus master device. Figure 4 shows a

typical application where up to four devices can be

connected to the bus, provided they have different

address settings. External pull-up resistors are not nec-

essary on these lines (when driven by push-pull dri-

vers), though these DACs can be used in applications

where pull-up resistors are required (such as in I

systems) to maintain compatibility with existing circuit-

ry. The serial interface operates at SCL rates up to

400kHz. The SDA state is allowed to change only while

SCL is low, with the exception of START and STOP con-

ditions as shown in Figure 5. Each transmission con-

sists of a START condition sent by the bus master

SCL

SDA

LOW

HIGH

HD:

STA

HD:

DAT

HD:

STA

SU:

DAT

SU:

STA

BUF

SU:

STO

START CONDITIONSTOP CONDITIONREPEATED START CONDITIONSTART CONDITION

Figure 3. 2-Wire Serial Interface Timing Diagram

µC

SDA SCL

OFFSET ADJUSTMENT

THRESHOLD ADJUSTMENT

GAIN ADJUSTMENT

IS OPTIONAL.

SCL

SDA

OUT

MAX5380M

2V REFERENCE

SCL

SDA

OUT

MAX5381N

4V REFERENCE

SCL

SDA

OUT

MAX5382P

REFERENCE

Figure 4. Typical Application Circuit

1 2 3 4 5 6 7 8 9 10 11 12

MAX5380/MAX5381/MAX5382 1

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