AD5744R Analog Devices, AD5744R Datasheet - Page 26

• Manufacturer Part Number: AD5744R
• Description: Complete Quad, 14-Bit, High Accuracy, Serial Input, Bipolar Voltage Output D/A Converter
• Manufacturer: Analog Devices

Specifications of AD5744R

• Resolution (bits): 14bit
• Dac Update Rate: 1MSPS
• Dac Settling Time: 8µs
• Max Pos Supply (v): +16.5V
• Single-supply: No
• Dac Type: Voltage Out
• Dac Input Format: Ser,SPI

AD5744R
DESIGN FEATURES
ANALOG OUTPUT CONTROL
In many industrial process control applications, it is vital that
the output voltage be controlled during power-up and during
brownout conditions. When the supply voltages are changing,
the VOUTx pins are clamped to 0 V via a low impedance path.
To prevent the output amp from being shorted to 0 V during this
time, Transmission Gate G1 is also opened (see Figure 42).
These conditions are maintained until the power supplies stabilize
and a valid word is written to the data register. G2 then opens, and
G1 closes. Both transmission gates are also externally controllable
via the reset in ( RSTIN ) control input. For example, if RSTIN is
driven from a battery supervisor chip, the RSTIN input is driven
low to open G1 and close G2 on power-off or during a brownout.
Conversely, the on-chip voltage detector output ( RSTOUT ) is
also available to the user to control other parts of the system.
The basic transmission gate functionality is shown in
PROGRAMMABLE SHORT-CIRCUIT PROTECTION
The short-circuit current (I
programmed by inserting an external resistor between the ISCC
pin and the PGND pin. The programmable range for the current is
500 μA to 10 mA, corresponding to a resistor range of 120 kΩ to
6 kΩ . The resistor value is calculated as follows:
R ≈
I
60
SC
VOLTAGE
CONTROL
MONITOR
AND
Figure 42. Analog Output Control Circuitry
RSTOUT
SC
) of the output amplifiers can be
G1
G2
RSTIN
VOUTA
AGNDA
Figure 42
Rev. E | Page 26 of 32
.
If the ISCC pin is left unconnected, the short-circuit current
limit defaults to 5 mA. It should be noted that limiting the short-
circuit current to a small value can affect the slew rate of the
output when driving into a capacitive load. Therefore, the value
of the short-circuit current that is programmed should take into
account the size of the capacitive load being driven.
DIGITAL I/O PORT
The AD5744R contains a 2-bit digital I/O port (D1 and D0).
These bits can be configured independently as inputs or outputs
and can be driven or have their values read back via the serial
interface. The I/O port signals are referenced to DV
When configured as outputs, they can be used as control signals
to multiplexers or can be used to control calibration circuitry
elsewhere in the system. When configured as inputs, the logic
signals from limit switches, for example, can be applied to D0
and D1 and can be read back using the digital interface.
DIE TEMPERATURE SENSOR
The on-chip die temperature sensor provides a voltage output that
is linearly proportional to the Celsius temperature scale. Its nom-
inal output voltage is 1.47 V at 25°C die temperature, varying at
5 mV/°C, giving a typical output range of 1.175 V to 1.9 V over the
full temperature range. Its low output impedance and linear output
simplify interfacing to temperature control circuitry and analog-to-
digital converters (ADCs). The temperature sensor is provided
as more of a convenience than as a precise feature; it is intended
for indicating a die temperature change for recalibration purposes.
LOCAL GROUND OFFSET ADJUST
The AD5744R incorporates a local ground offset adjust feature
that, when enabled in the function register, adjusts the DAC
outputs for voltage differences between the individual DAC ground
pins and the REFGND pin, ensuring that the DAC output voltages
are always referenced to the local DAC ground pin. For example, if
the AGNDA pin is at +5 mV with respect to the REFGND pin, and
VOUTA is measured with respect to AGNDA, a −5 mV error
results, enabling the local ground offset adjust feature to adjust
VOUTA by +5 mV, thereby eliminating the error.
Data Sheet
CC
and DGND.