MAX513ESD Datasheet MAX512CSD+T, MAX513EPD, MAX512ESD | P10-P12

SDIN

SCLK

Q2 Q1 SC SB SA LC LB LA D7 D6 D5 D4 D3 D2 D1 D0

OPTIONAL

INSTRUCTION

EXECUTED

(CONTROL BYTE) (DATA BYTE)

Figure 2. MAX512/MAX513 3-Wire Serial-Interface Timing Diagram

MAX512/MAX513

Low-Cost, Triple, 8-Bit Voltage-Output DACs

with Serial Interface

10 ______________________________________________________________________________________

Shutdown Mode

When programmed to shutdown mode, the outputs of

DAC A and B go into a high-impedance state. Virtually

no current flows into or out of the buffer amplifiers in

that state. The output of DAC C goes to 0V when shut

down. In shutdown mode, the REF_ inputs are high

impedance (2MΩ typ) to conserve current drain from

the system reference; therefore, the system reference

does not have to be powered down. The logic output

LOUT remains active in shutdown.

Coming out of shutdown, the DAC outputs return to the

values kept in the registers. The recovery time is equiv-

alent to the DAC settling time.

Reset

The

–

—

–

input is active low. When asserted (

–

—

–

= 0), DACs A and B are set to full scale (FFhex) and

active, while DAC C is set to zero code (00hex) and

active. The 16-bit serial register is cleared to 0000hex.

LOUT is reset to zero.

Serial Interface

An active-low chip select (

–

—

–

) enables the shift register

to receive data from the serial data input. Data is

clocked into the shift register on every rising edge of

the serial clock signal (SCLK). The clock frequency can

be as high as 5MHz.

Data is sent MSB first and can be transmitted in one

16-bit word. The write cycle can be interrupted at any

time when

–

—

–

is kept active (low) to allow, for example,

two 8-bit-wide transfers. After clocking all 16 bits into

the input shift register, the rising edge of

–

—

–

updates

the DAC outputs, the shutdown status, and the status of

the logic output. Because of their single buffered struc-

ture, DACs cannot be simultaneously updated to differ-

ent digital values.

Table 1. Input Shift Register

**Clocked in last.

**Clocked in first.

Uncommitted BitQ2**

Logic OutputQ1

Shut Down DAC C, Active HighSC

Shut Down DAC B, Active HighSB

Shut Down DAC A, Active HighSA

Load Reg DAC C, Active HighLC

Load Reg DAC B, Active HighLB

Load Reg DAC A, Active HighLA

DAC Data Bit 7 (MSB)B7

DAC Data Bit 6B6

DAC Data Bit 5B5

DAC Data Bit 4B4

DAC Data Bit 3B3

DAC Data Bit 2B2

DAC Data Bit 1B1

DAC Data Bit 0 (LSB)B0*

DATA BITSCONTROL BITS

MAX512/MAX513

Low-Cost, Triple, 8-Bit Voltage-Output DACs

with Serial Interface

______________________________________________________________________________________ 11

Serial-Input Data Format and Control Codes

Table 2 lists the serial-input data format. The 16-bit

input word consists of an 8-bit control byte and an 8-bit

data byte. The 8-bit control byte is not decoded inter-

nally. Every control bit performs one function. Data is

clocked in starting with Q2 (uncommitted bit), followed

by the remaining control bits and the data byte. The

LSB of the data byte (B0) is the last bit clocked into the

shift register (Figure 2).

Example of a 16-bit input word:

The example above performs the following functions:

• 80hex (128 decimal) loaded into DAC registers

A and B.

• Content of the DAC C register remains unchanged.

• DAC A and DAC B are active.

• DAC C is shut down.

• LOUT is reset to 0.

Digital Inputs

The digital inputs are compatible with CMOS logic.

Supply current increases slightly when toggling the

logic inputs through the transition zone between

(0.3)(V

) and (0.7)(V

Digital Output

The latched digital output (LOUT) has a 1.6mA source

capability while maintaining a (V

- 0.4V) output level.

With a 1.6mA sink current, the output voltage is guaran-

teed to be no more than 0.4V. The output can be used

for digital auxiliary control. Please note that the digital

output remains fully active during shutdown mode.

Microprocessor Interfacing

The MAX512/MAX513 serial interface is compatible with

Microwire, SPI, and QSPI. For SPI and QSPI, clear the

CPOL and CPHA bits (CPOL = 0 and CPHA = 0).

CPOL = 0 sets the inactive state of clock to zero and

CPHA = 0 changes data at the falling edge of SCLK.

This setting allows both SPI and QSPI to run at full clock

speeds (0.5MHz and 4MHz, respectively). If a serial port

is not available on your µP, three bits of a parallel port

can be used to emulate a serial port by bit manipulation.

Minimize digital feedthrough at the voltage outputs by

operating the serial clock only when necessary.

CONTROL DATA

Q2 Q1 SC SB SA LC LB LA B7 B4 B3 B2 B1 B0

FUNCTION

* * * *

* 0 0 0 X X X X X X X X No Operation to DAC Registers

* 8-Bit DAC Data Load Register to DAC C

* 8-Bit DAC Data Load Register to DAC B

* 8-Bit DAC Data Load Register to DAC A

* 8-Bit DAC Data Load All DAC Registers

* * 0 0 0 * * * X X X X X X X X All DACs Active

* * 1 0 0 * * * X X X X X X X X Shut Down DAC C

* * 0 1 0 * * * X X X X X X X X Shut Down DAC B

* * 0 0 1 * * * X X X X X X X X Shut Down DAC A

* * 1 1 1 * * * X X X X X X X X Shut Down All DACs

X 0 * * * * * * X X X X X X X X Reset LOUT

X 1 * * * * * * X X X X X X X X Set LOUT

B5B6

Table 2. Serial-Interface Programming Commands

Don’t care.

* Not shown for clarity. The functions of loading and shutting down the DACs and programming the logic can be combined in a single command.

MSB LSB

* *

X 0 1 0 0 0 1 1 1 0 0 0 0 0 0 0

Q2 Q1 SC SB SA LC LB LA B7 B6 B5 B4 B3 B2 B1 B0

Loaded Loaded

in First in Last

MAX512/MAX513

Low-Cost, Triple, 8-Bit Voltage-Output DACs

with Serial Interface

12 ______________________________________________________________________________________

_____________

Applications Information

Power-Supply and Reference

Operating Ranges

The MAX512 is fully specified to operate with

= 5V ±10% and V

= GND = 0V. The MAX513 is

specified for single-supply operation with V

ranging from

2.7V to 3.6V, covering all commonly used supply voltages

in 3V systems. The MAX512/MAX513 can also be used

with a negative supply ranging from -1.5V to -5.5V. Using a

negative supply typically improves zero-code error and

settling time (as shown in the

Typical Operating

Characteristics

graphs).

The two separate reference inputs for the DAC pair A/B

and the unbuffered output C allow different full-scale out-

put voltages and, if a negative supply is used, also allow

different polarity. In dual-supply mode, REFAB can vary

from V

to (V

- 1.5V). In single-supply mode, the

specified range for REFAB is 0V to V

. REFC can range

from GND to V

. Do not force REFC below ground.

Power-supply sequencing is not critical. If a negative sup-

ply is used, make sure V

is never more than 0.3V above

ground. Do not apply signals to the digital inputs until the

device is powered-up. If this is not possible, add current-

limiting resistors to the digital inputs.

Power-Supply Bypassing and

Ground Management

In single-supply operation (V

= GND), GND and V

should be connected to the highest quality ground

available. Bypass V

with a 0.1µF to 0.22µF capacitor

to GND. For dual-supply operation, bypass V

with a

0.1µF to 0.22µF capacitor to GND. Reference inputs

can be used without bypassing. For optimum line/load-

transient response and noise performance, bypass the

reference inputs with 0.1µF to 4.7µF to GND. Careful

PC board layout minimizes crosstalk among DAC out-

puts, reference inputs, and digital inputs. Separate ana-

log lines with ground traces between them. Make sure

that high-frequency digital lines are not routed in paral-

lel to analog lines.

Unipolar Output

With unipolar output, the output voltage and the refer-

ence voltage are the same polarity. The MAX512/

MAX513 can be used with a single supply if the refer-

ence voltages are positive. With a negative supply,

the REFAB voltage can vary from V

approximately (V

- 1.5V), allowing two-quadrant mul-

tiplication.

SCLK

DIN

LOUT

CSS

CSPWH

CSH

Figure 3. MAX512/MAX513 Detailed Serial-Interface Timing Diagram

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P16

MAX513ESD

Mfr. #:

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Digital to Analog Converters - DAC Low-Cost, Triple, 8-Bit Voltage-Output DACs with Serial Interface

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