AD5737 16-Bit, Low-Power, Buffered Output, Rail-to-Rail DAC

The AD5737 is a quad-channel current output digital-to-analog converter (DAC) from Analog Devices. This DAC offers four independently programmable output channels, each capable of providing a current output. In addition, each channel of the AD5737 includes a corresponding CHART pin, which allows HART signals to be coupled to the current output of the AD5737. This feature is useful in applications where HART communication is required. It has an input power supply range from 10.8 V to 33 V. The AD5737 includes on-chip dynamic power control, which is used to minimize package power dissipation. This is achieved by regulating the voltage on the output driver within a range of 7.4 V to 29.5 V. The AD5737's versatile interface makes it compatible with a wide range of communication standards like SPI, QSPI, MICROWIRE, DSP etc. which can be very convenient for various system integration needs. It is commonly used in applications where precise current control is required, such as in industrial automation, instrumentation, and control systems. 

AD5737 Pinout Configuration

Here are the pinout details for AD5737.        

Pin Number	Name	Function
1	RSET_B	External Current Setting Resistor section.
2	RSET_A	External Current Setting Resistor section.
3	REFGND	Ground Reference Point for Internal Reference.
4	REFGND	Ground Reference Point for Internal Reference.
5	AD0	Address Decode for the Device Under Test (DUT) on the Board.
6	AD1	Address Decode for the DUT on the Board.
7	SYNC	Frame Synchronization Signal for the Serial Interface
8	SCLK	Serial Clock Input
9	SDIN	Serial Data Input.
10	SDO	Serial Data Output.
11	DVDD	Digital Supply Pin.
12	DGND	Digital Ground.
13	LDAC	Load DAC
14	CLEAR	CLEAR
15	ALERT	Alert
16	FAULT	Active Low, Open-Drain Output.
17	DGND	Digital Ground.
18	RESET	Hardware Reset
19	AVDD	Positive Analog Supply Pin.
20	NC	No Connect.
21	CHARTA	HART Input Connection
22	IGATEA	Optional Connection for External Pass Transistor.
23	COMPDCDC_A	DC-to-DC Compensation Capacitor..
24	VBOOST_A	Supply for Channel A Current Output Stage.
25	NC	No Connect.
26	IOUT_A	Current Output Pin for DAC Channel A.
27	AGND	Ground Reference Point for Analog Circuitry.
28	NC	No Connect. Do not connect to this pin.
29	CHARTB	HART Input Connection for DAC Channel B. For more information, see the HART Connectivity section.
30	NC	No Connect. Do not connect to this pin.
31	IGATEB	Optional Connection for External Pass Transistor.
32	COMPDCDC_B	DC-to-DC Compensation Capacitor. Connect a 10 nF capacitor from this pin to ground.
33	IOUT_B	Current Output Pin for DAC Channel B.
34	VBOOST_B	Supply for Channel B Current Output Stage
35	AGND	Ground Reference Point for Analog Circuitry. This pin must be connected to 0 V.
36	SWB	Switching Output for Channel B DC-to-DC Circuitry.
37	GNDSWB	Ground Connection for DC-to-DC Switching Circuit. This pin must always be connected to ground.
38	GNDSWA	Ground Connection for DC-to-DC Switching Circuit. This pin must always be connected to ground.
39	SWA	Switching Output for Channel A DC-to-DC Circuitry.
40	AGND	Ground Reference Point for Analog Circuitry. This pin must be connected to 0 V.
41	SWD	Switching Output for Channel D DC-to-DC Circuitry
42	GNDSWD	Ground Connection for DC-to-DC Switching Circuit. This pin must always be connected to ground.
43	GNDSWC	Ground Connection for DC-to-DC Switching Circuit. This pin must always be connected to ground.
44	SWC	Switching Output for Channel C DC-to-DC Circuitry.
45	AVCC	Supply for DC-to-DC Circuitry. The voltage range is from 4.5 V to 5.5 V.
46	VBOOST_C	Supply for Channel C Current Output Stage
47	IOUT_C	Current Output Pin for DAC Channel C.
48	COMPDCDC_C	DC-to-DC Compensation Capacitor.
49	IGATEC	Optional Connection for External Pass Transistor.
50	NC	No Connect.
51	CHARTC	HART Input Connection for DAC Channel C.
52	NC	No Connect.
53	AGND	Ground Reference Point for Analog Circuitry.
54	IOUT_D	Current Output Pin for DAC Channel D.
55	NC	No Connect.
56	VBOOST_D	Supply for Channel D Current Output Stage.
57	COMPDCDC_D	DC-to-DC Compensation Capacitor.
58	IGATED	Optional Connection for External Pass Transistor
59	CHARTD	HART Input Connection for DAC Channel D.
60	NC	No Connect. Do not connect to this pin.
61	REFIN	External Reference Voltage Input.
62	REFOUT	Internal Reference Voltage Output.
63	RSET_D	An external, precision, low drift, 15 kΩ current setting resistor can be connected to this pin to improve the IOUT_D temperature drift performance. For more information, see the External Current Setting Resistor section.
64	RSET_C	An external, precision, low drift, 15 kΩ current setting resistor can be connected to this pin to improve the IOUT_C temperature drift performance. For more information, see the External Current Setting Resistor section.

Features of AD5737 

AD5737 ADC chip has the following key features:

• 12-bit resolution and monotonicity
• Dynamic power control for thermal management or external PMOS mode
• Current output ranges: 0 mA to 20 mA, 4 mA to 20 mA,
• and 0 mA to 24 mA
• ±0.1% total unadjusted error (TUE) maximum User-programmable offset and gain
• On-chip diagnostics
• On-chip reference: ±10 ppm/°C maximum
• −40°C to +105°C temperature range

Manufacturers of AD5737:

The AD5737 is manufactured by Analog Devices (earlier this IC was from Maxim Integrated). There are no alternative manufacturers for the same part number as of the date of writing this article. 

AD5737 Equivalents

There is no pin-to-pin compatible equivalent for AD5737 we could find at the time of writing this.

AD5737 Alternatives

If you are looking for an alternative for AD5737 you can look at the other IC from these.

DAC8562, MCP4725, MCP4921, PT8211, DAC0832, DAC0808, DAC7715, AD5421

Note: Complete technical details can be found in the AD5737 datasheet at this page’s end.

AD5737 Circuit Diagram

The above image shows the AD5737 in a circuit design for a HART-enabled output module, specifically for use in an industrial control application.

The design provides for a HART-enabled current output, with the HART capability provided by the AD5700/AD5700-1 HART modem, the industry’s lowest power and smallest footprint HART-compliant IC modem. For additional space savings, the AD5700-1 offers a 0.5% precision internal oscillator. The HART_OUT signal from the AD5700 is attenuated and ac-coupled into the CHARTx pin of the AD5737. Such a configuration results in the AD5700 HART modem output modulating the 4 mA to 20 mA analog current without affecting the dc level of the current. This circuit adheres to the HART physical layer specifications as defined by the HART Communication Foundation. For transient overvoltage protection, a 24 V transient voltage suppressor (TVS) is placed on the IOUT/VOUT connection. For added protection, clamping diodes are connected from the IOUT_x/VOUT_x pin to the AVDD and GND power supply pins. A 5 kΩ current limiting resistor is also placed in series with the +VSENSE_x input. This is to limit the current to an acceptable level during a transient event. The recommended external band-pass filter for the AD5700 HART modem includes a 150 kΩ resistor, which limits current to a sufficiently low level to adhere to intrinsic safety requirements. In this case, the input has higher transient voltage protection and, therefore, does not require additional protection circuitry, even in the most demanding of industrial environments.

AD5737 Troubleshooting Guide

My AD5737 is not providing any output. What could be the issue?

First, ensure that the power supply voltages are within the specified range (10.8 V to 33 V). Check the connections to the AD5737, including VDD, GND, and the reference voltage. 

My circuits show a lot of noise, how to reduce it?

Should use bypass capacitors in between VDD and GND. Use a solid ground plane and connect it directly to the DAC's ground pin. Avoid ground loops and minimize the length of high-current ground paths.

Does the AD5737 interfere with EMF signals?

Yes, the AD5737 will interfere with EMF lines so Consider using shielding techniques to protect the DAC from external electromagnetic interference.

Things to Consider When Using AD5737 in Your Design

When designing with the AD5737, digital-analog Converter (ADC), here are some important considerations and design tips to keep in mind:

Microprocessor Interfacing

Microprocessor interfacing to the AD5737 is via a serial bus that uses a protocol compatible with microcontrollers and DSP processors. The communication channel is a 3-wire minimum interface consisting of a clock signal, a data signal, and a latch signal. The AD5737 requires a 24-bit data-word with data valid on the falling edge of SCLK. The DAC output update is initiated either on the rising edge of LDAC or, if LDAC is held low, on the rising edge of SYNC. The contents of the registers can be read using the readback function.

Traces

The power supply lines of the AD5737 must use as large a trace as possible to provide low impedance paths and reduce the effects of glitches on the power supply line. Fast-switching signals such as clocks must be shielded with digital ground to prevent radiating noise to other parts of the board and must never be run near the reference inputs. A ground line routed between the SDIN and SCLK traces helps reduce crosstalk between them (not required on a multilayer board that has a separate ground plane, but separating the lines helps). It is essential to minimize noise on the REFIN line because it couples through to the DAC output.
Avoid crossover of digital and analog signals. Traces on opposite sides of the board must run at right angles to each other.
to reduce the effects of feedthrough on the board. A microstrip technique is by far the best method, but it is not always possible with a double-sided board. In this technique, the component side of the board is dedicated to the ground plane, and signal traces are placed on the solder side.

DC-to-DC Converters

To achieve high efficiency, good regulation, and stability, a well-designed printed circuit board layout is required.

Follow these guidelines when designing printed circuit boards.

• Keep the low ESR input capacitor, CIN, close to AVCC and PGND.
• Keep the high current path from CIN through the inductor (LDCDC) to SWx and PGND as short as possible.
• Keep the high current path from CIN through the inductor (LDCDC), the diode (DDCDC), and the output capacitor (CDCDC) as short as possible.
• Keep high current traces as short and as wide as possible. The path from CIN through the inductor (LDCDC) to SWx and PGND must be able to handle a minimum of 1 A.
• Place the compensation components as close as possible to the COMPDCDC_x pin.
• Avoid routing high impedance traces near any node connected to SWx or near the inductor to prevent radiated noise injection.

Layout Guidelines

 Grounding- In any circuit where accuracy is important, careful consideration of the power supply and ground return layout helps to ensure the rated performance. The printed circuit board on which the AD5737 is mounted must be designed so that the analog and digital sections are separated and confined to certain areas of the board. If the AD5737 is in a system where multiple devices require an AGND-to-DGND connection, the connection must be made at one point only. The star ground point must be established as close as possible to the device. The GNDSWx pin and the ground connection for the AVCC supply are referred to as PGND. PGND must be confined to certain areas of the board, and the PGND-to-AGND connection must be made at one point only.

Supply Decoupling- The AD5737 must have ample supply bypassing of 10 μF in parallel with 0.1 μF on each supply, located as close to the package as possible, ideally right up against the device. The 10 μF capacitors are the tantalum bead type. The 0.1 μF capacitors must have low effective series resistance (ESR) and low effective series inductance (ESL), such as the common ceramic types, which provide a low impedance path to ground at high frequencies to handle transient currents due to internal logic switching.

Applications of AD5737

• Process control
• Actuator control
• PLCs
• HART network connectivity

AD5737 Footprint Information

Here you can find the mechanical drawings of AD5737 along with its dimensions. The dimensions can be used to create custom footprints of the module and be used for PCB or CAD modeling.