AD5544ARS datasheet(12/16 Pages) AD

12 / 16 page

REV. 0

AD5544/AD5554

–12–

CLOCK FREQUENCY – Hz

100

10k

100k

100

VDD = 5V 10%

TA = 25 C

TPC 17. AD5544/AD5554 Power Supply Rejection

vs. Frequency

TEMPERATURE – C

–50

VDD = 5V

VREF = 10V

LOGIC = VDD

–25

100

125

150

TPC 18. AD5544/AD5554 Power Supply Current

vs. Temperature

LOGIC INPUT VOLTAGE – Volts

600

VDD = 5V

VREF = 10V

TA = 25 C

500

400

300

200

100

12345

TPC 19. AD5544/AD5554 Power Supply Current

vs. Logic Input Voltage

CIRCUIT OPERATION

The AD5544 and AD5554 contain four, 16-bit and 14-bit,

current-output, digital-to-analog converters respectively. Each

DAC has its own independent multiplying reference input. Both

AD5544/AD5554 use 3-wire SPI compatible serial data inter-

face, with a conﬁgurable asynchronous

RS pin for half-scale

(MSB = 1) or zero-scale (MSB = 0) preset. In addition, an

LDAC strobe enables four channel simultaneous updates for

hardware synchronized output voltage changes.

D/A Converter Section

Each part contains four current-steering R-2R ladder DACs.

Figure 4 shows a typical equivalent DAC. Each DAC contains

a matching feedback resistor for use with an external I-to-V

converter ampliﬁer. The RFBX pin is connected to the output of

the external ampliﬁer. The IOUTX terminal is connected to the

inverting input of the external ampliﬁer. The AGNDX pin should

be Kelvin-connected to the load point in the circuit requiring

the full 16-bit accuracy. These DACs are designed to operate

with both negative or positive reference voltages. The VDD power

pin is only used by the logic to drive the DAC switches ON and

OFF. Note that a matching switch is used in series with the

internal 5 k

Ω feedback resistor. If users are attempting to mea-

sure the value of RFB, power must be applied to VDD in order to

achieve continuity. An additional VSS bias pin is used to guard

the substrate during high temperature applications to minimize

zero-scale leakage currents that double every 10

°C. The DAC

output voltage is determined by VREF and the digital data (D) as:

OUT

REF

=−

65536

(For AD5544)

(Equation 1)

OUT

REF

=−

16384

(For AD5554)

(Equation 2)

Note that the output polarity is opposite to the VREF polarity for

dc reference voltages.

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