Part A
AD7747ARUZ
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 3952 Stückzahl
- Package
- TSSOP-16
- Series
- Datenerfassung von ADCs-DACs für besonderen Zweck
Replacement verdict
Not a drop-in replacement
The AD7747ARUZ and AD7740KRM are not drop-in replacements for one another. The AD7747ARUZ is a 24-bit capacitance-to-digital converter with a 16-bit resolution and I2C interface, while the AD7740KRM is a 16-bit voltage-to-frequency converter with a synchronous clock input. Their differing conversion architectures, output types, and package footprints make them functionally incompatible for direct substitution.
Different conversion architecture
Different output type
Different package footprint
Different interface type
Parts at a glance
Part B
AD7740KRM
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 3992 Stückzahl
- Package
- TSSOP-8
- Series
- PMIC-Konverter für PvV-F und F-V
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | AD7747ARUZ | AD7740KRM | Why it matters |
|---|---|---|---|
| Resolution | 24-bit (Capacitance-to-Digital Converter) | 12-bit (Voltage-to-Frequency Converter) | Resolution determines the smallest measurable change; the AD7747 offers far higher precision for capacitive sensing, while the AD7740 is a lower-resolution VFC. |
| Primary Function | Capacitance-to-Digital Converter (CDC) | Voltage-to-Frequency Converter (VFC) | The core function differs fundamentally; one measures capacitance directly while the other converts an analog voltage to a frequency, so they are not functionally interchangeable. |
| Input Type | Differential capacitance input | Single-ended voltage input | The input signal type must match the sensor; a capacitive sensor cannot drive a voltage-input VFC without additional circuitry. |
| Output Interface | I2C digital (2-wire serial) | Frequency output (pulse train) | The output format dictates how the host system reads data; I2C requires a digital bus, while a frequency output requires a counter/timer. |
| Supply Voltage | 2.7 V to 5.25 V | 3.0 V to 5.25 V (single supply) | Supply range affects compatibility with the system rail; the AD7747 supports slightly lower minimum voltage. |
| Package | 16-lead TSSOP | 8-lead MSOP | Package footprint and pin count affect PCB layout and cannot be directly substituted without a board redesign. |
| Operating Temperature Range | -40°C to +125°C | -40°C to +85°C | The wider temperature range of the AD7747 suits harsher environments, while the AD7740 is limited to standard industrial ranges. |
| Typical Application | Precision capacitive sensing (pressure, humidity, position) | Signal isolation, analog-to-frequency conversion, simple ADC | Intended applications differ, so substitutability depends on whether the design needs capacitance measurement or voltage-to-frequency conversion. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD7747ARUZ | AD7740KRM |
|---|---|---|
| Part Status | Active | Obsolete |
| Type | Capacitance-to-Digital Converter | Voltage to Frequency |
| Frequency - Max | - | 1 MHz |
| Full Scale | - | ±50ppm/°C |
| Linearity | - | ±0.012% |
| Mounting Type | Surface Mount | Surface Mount |
| Number of Channels | 2 | - |
| Resolution(Bits) | 24 b | - |
| Data Interface | Serial | - |
| Voltage Supply Source | Single Supply | - |
| Voltage - Supply | 2.7V ~ 5.25V | - |
| Operating Temperature | -40°C ~ 125°C | - |
Frequently asked questions
What are the primary functional differences between the AD7747ARUZ and the AD7740KRM?
The AD7747ARUZ is a 24-bit capacitance-to-digital converter (CDC) with a ±8 pF input range and I2C interface, designed for floating capacitive sensors. The AD7740KRM is a synchronous voltage-to-frequency converter (VFC) with a 0.1 MHz to 1 MHz output frequency range and a 2.7 V to 5.25 V supply, intended for analog signal isolation and conversion. They serve fundamentally different measurement functions and are not interchangeable.
Do the AD7747ARUZ and AD7740KRM use the same package and pinout?
No. The AD7747ARUZ is supplied in a 16-lead TSSOP package, while the AD7740KRM is supplied in an 8-lead MSOP package. The pin counts, pin functions, and PCB land patterns differ, so neither part can be dropped into the other's footprint.
What are the supply voltage requirements for each device?
The AD7747ARUZ operates from a single 2.7 V to 5.25 V supply. The AD7740KRM also operates from a 2.7 V to 5.25 V supply. Both are specified over the −40 °C to +125 °C temperature range, but their internal architectures and output interfaces differ.
What output interface does each device provide?
The AD7747ARUZ provides a 24-bit digital capacitance reading over an I2C-compatible serial interface. The AD7740KRM provides a frequency output proportional to the input voltage, with the output frequency ranging from 0.1 MHz to 1 MHz. The AD7747ARUZ is read digitally by a host controller, whereas the AD7740KRM output is typically measured by a counter or timer.
Can the AD7747ARUZ and AD7740KRM be used in the same application?
They are not substitutes. The AD7747ARUZ is intended for direct capacitance measurement of floating sensors, while the AD7740KRM is intended for voltage-to-frequency conversion. A design requiring capacitance-to-digital conversion should use the AD7747ARUZ; a design requiring a voltage-to-frequency converter should use the AD7740KRM. Each part must be selected based on the measured quantity and system interface.
What is the input range of the AD7747ARUZ compared with the AD7740KRM?
The AD7747ARUZ has a specified capacitance input range of ±8 pF with a resolution of 24 bits. The AD7740KRM accepts an analog voltage input and produces a corresponding output frequency; its input is voltage, not capacitance. Because the input quantities differ, their input ranges cannot be compared directly.
Are both devices available in production quantities from authorized distributors?
Both the AD7747ARUZ and AD7740KRM are listed as active products by Analog Devices and are stocked by authorized distributors such as DigiKey and Mouser. Designers should confirm current lifecycle status and availability against the manufacturer's product page before committing to a design.