MAX5364 Просмотр технического описания (PDF) - Maxim Integrated

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MAX5364

Low-Cost, Low-Power, 6-Bit DACs with 3-Wire Serial Interface in SOT23

Maxim Integrated 

Low-Cost, Low-Power, 6-Bit DACs with 3-Wire

Serial Interface in SOT23

input register, it transfers its contents to the DAC latch

on CS’s low-to-high transition (Figure 3). Note that if CS

is not kept low during the entire 16 SCLK cycles, data

will be corrupted. In this case, reload the DAC latch

with a new 16-bit word. The serial clock (SCLK) can

idle either high or low between transitions. Figure 4

shows the complete 3-wire serial interface transmission.

Table 3 lists serial interface mapping.

Applications Information

Device Powered by an External Reference

Since the MAX5365 generates an output voltage pro-

portional to VDD, a noisy power supply will affect the

accuracy of the on-board reference, thereby affecting

the overall accuracy of the DAC. The circuit in Figure 5

rejects this power-supply noise by powering the device

directly with a precision voltage reference, improving

overall system accuracy. The MAX6103 (+3V, 75ppm)

or the MAX6105 (+5V, 75ppm) precision voltage refer-

ences are ideal choices due to the low power require-

ments of the MAX5365. This solution is also useful

when the required full-scale output voltage is different

from the available supply voltages.

Digital Inputs and Interface Logic

The digital interface for the 6-bit DAC is based on a

3-wire standard that is compatible with SPI, QSPI, and

MICROWIRE interfaces. The three digital inputs (CS, DIN,

and SCLK) load the digital input serially into the DAC.

All of the digital inputs include Schmitt-trigger buffers to

accept slow-transition interfaces. This means that opto-

couplers can interface directly to the MAX5363/

MAX5364/MAX5365 without additional external logic.

The digital inputs are compatible with CMOS logic levels

and can be driven with voltages up to +5.5V regardless

of the supply voltage.

Power-Supply Bypassing and Layout

Careful PC board layout is important for best system

performance. To reduce crosstalk and noise injection,

keep analog and digital signals separate. To ensure

that the ground return from GND to the supply ground

is short and low impedance, a ground plane is recom-

mended. Bypass VDD with a 0.1µF to ground as close

as possible to the device. If the supply is excessively

noisy, connect a 10Ω resistor in series with the supply

and VDD and add additional capacitance.

Table 2. Shutdown Modes

DAC CODE

[D13 AND D12]

01

10

11

MODE

Shutdown

Shutdown

Shutdown

OUTPUT RESISTANCE TO

GROUND (Ω)

1k

100k

1M

MAXIMUM SUPPLY

CURRENT ( µA)

1

1

1

Table 3. Serial Interface Mapping

MSB

XX00

XX00

XX00

XX00

16-BIT SERIAL WORD

0000

1111

0000

1000

0000

11XX

01XX

00XX

XX01

XXXX

XXXX

XX10

XXXX

XXXX

XX11

X = Don’t care

XXXX

XXXX

LSB

XXXX

XXXX

XXXX

XXXX

XXXX

XXXX

XXXX

ANALOG

OUTPUT

0V

VREF ✕ (63/64)

VREF ✕ (1/64)

VREF ✕ (32/64)

0V

0V

0V

FUNCTION

Normal operation

Normal operation

Normal operation

Normal operation

Shutdown,

1kΩ to GND

Shutdown,

100kΩ to GND

Shutdown,

1MΩ to GND

_______________________________________________________________________________________ 9

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