AD5770R datasheet(26/59 Pages) AD

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AD5770R

Data Sheet

Rev. 0 | Page 26 of 59

and bypassed on power up. The multiplexer buffer is enabled by

setting the MUX_BUFFER bit in the MONITOR_SETUP register.

Compliance Voltage Monitoring

When the MON_FUNCTION bits in the MONITOR_

SETUP register are set to select output voltage monitoring, the

output compliance voltage of the selected DAC channel is

multiplexed onto the MUX_OUT pin. The IDACx channel to

be monitored is selected using the MON_CH bits in the

MONITOR_SETUP register.

Output Current Monitoring

When the MON_FUNCTION bits in the MONITOR_SETUP

of the output current of the selected DAC channel is multiplexed

onto the MUX_OUT pin. The output current can only be

monitored in current sourcing mode. The IDACx channel to be

monitored is selected using the MON_CH bits in the MONITOR_

SETUP register.

The output current is calculated by

(

)

−

400 mV

FULLSCALE

MUX

SOURCE

(1)

where:

ISOURCE is the output current being sourced.

IFULLSCALE is the full-scale output current.

VMUX is the measured voltage at the MUX_OUT pin.

VOS is the monitor offset voltage, nominally 28 mV.

Uncalibrated, the current monitoring feature is accurate to

within 10% of the full-scale output range. To improve the

accuracy of the current monitor feature, calibrate VOS by

measuring the voltage at the MUX_OUT pin at zero scale. To

calibrate the 400 mV term, measure the voltage at the

MUX_OUT pin at full scale.

For 0 mA to 140 mA low headroom mode on Channel 1, use a

value of 250 mA for IFULLSCALE.

Internal Die Temperature Monitoring

When temperature monitoring is selected in the MONITOR_

SETUP register, a voltage representation of the internal die

temperature is multiplexed onto the MUX_OUT pin. To monitor

the internal die temperature, a precision current is forced through a

diode on the chip, and the voltage across the diode is multiplexed

onto the MUX_OUT pin. Choose to use an external bias current

for the temperature monitoring function by setting the

IB_EXT_EN bit high in the MONITOR_SETUP register. The

external bias current must be forced into the MUX_OUT pin.

The multiplexer buffer must be bypassed when using an

external bias current for temperature monitoring.

Using the internal bias current with the IB_EXT_EN bit set low,

calculate the internal die temperature as follows:

700 mV

1.8 mV

−

(2)

where:

T is the die temperature (°C).

VD is the diode voltage.

Using an external bias current of 100 µA, with the IB_EXT_EN

bit set high, the internal die temperature can be calculated as

follows:

880 mV

1.3 mV

−

(3)

When using an external bias current of 200 µA, with the

IB_EXT_EN bit set high, the die temperature can be calculated

as follows:

1.04 V

0.9 mV

−

(4)

SERIAL INTERFACE

The AD5770R has a 4-wire (CS, SCLK, SDI, and SDO) interface

that is compatible with SPI, QSPI, and MICROWIRE interface

standards as well as most digital signal processors (DSPs).

For both read and write SPI transactions, data must be valid on

the rising edge of SCLK (SCLK clock polarity = 0, SCLK clock

phase = 0). For all SPI transactions, data is shifted MSB first.

Communication with the device is separated into two distinct

phases of operation. The first phase is the instruction phase and

is used to initiate some action of the device. The second phase is

the data phase where data is either passed to the device to operate

on or received from the device in response to the instruction

phase. Figure 71 illustrates the SPI transaction phases.

SDI

SDO

R/W

DATA BYTE

7-BIT ADDRESS

DATA BYTE

INSTRUCTION PHASE

DATA BYTE

DATA PHASE

Figure 71. SPI Transaction Phases

Instruction Phase

The instruction phase immediately follows the falling edge of

CS that initiates the SPI transaction. The instruction phase

consists of a read/write bit (R/W) followed by a register address

word. Setting R/W high selects a read instruction. Setting R/W

low selects a write instruction. The address word is 7 bits long.

The register address sent in the instruction phase is used as the

starting address to start writing or reading from. Refer to Table

12 and Table 13 for a full list of registers and the associated

addresses.

Data Phase

The data phase immediately follows the instruction phase.

When a write instruction is sent to the device, data is written to

the register location selected. When a read instruction is sent to

the device, data stored in the register location selected is shifted

out on the SDO pin.

AD5770R Datasheet(PDF) 26 Page - Analog Devices

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