Part A
AD7740KRMZ
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 3022 PCS
- Package
- TSSOP-8
- Series
- Convertisseurs PMIC - V - F et F - V
Replacement verdict
Not a drop-in replacement
The AD7747ARUZ and AD7740KRMZ are not functionally interchangeable despite sharing the Analog Devices capacitance-to-digital converter family lineage. The AD7747ARUZ is a 24-bit sigma-delta capacitance-to-digital converter with true differential input and on-chip temperature sensor, while the AD7740KRMZ is a 16-bit voltage-output capacitance-to-voltage converter requiring an external reference and clock. Their resolution, output architecture, interface, and package footprints differ fundamentally, so substituting one for the other requires full circuit redesign and firmware revalidation.
Different output type
Different resolution class
Different interface protocol
Different package footprint
Parts at a glance
Part B
AD7747ARUZ
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 3952 PCS
- Package
- TSSOP-16
- Series
- Acquisition de données - ADC DAC - dédié
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 | AD7740KRMZ | Why it matters |
|---|---|---|---|
| Resolution | 24-bit (Capacitance-to-Digital Converter) | 12-bit (Voltage-to-Frequency Converter) | Determines measurement precision; the AD7747 offers far higher resolution for capacitive sensing, while the AD7740 provides coarser V/F conversion. |
| Primary Function | Capacitance-to-Digital Converter (CDC) | Voltage-to-Frequency Converter (VFC) | These are fundamentally different signal-chain functions, so they are not direct substitutes in a given circuit. |
| Input Type | Differential capacitance input | Single-ended voltage input | Defines what physical quantity the device measures; capacitive sensors require the AD7747, while analog voltage signals suit the AD7740. |
| Output Interface | I2C digital (2-wire serial) | Frequency output (pulse train) | Determines how the host system reads data; I2C is directly bus-compatible, whereas the AD7740 requires a frequency counter. |
| Supply Voltage | 2.7 V to 5.25 V | 3.0 V to 5.25 V (single supply) | Affects power-rail compatibility; the AD7747 tolerates slightly lower supply voltages than the AD7740. |
| Package | 16-lead TSSOP | 8-lead MSOP | Footprint and pin count differ, so PCB layout and assembly are not interchangeable between the two parts. |
| Operating Temperature Range | -40°C to +125°C | -40°C to +85°C | The AD7747 supports higher ambient temperatures, which matters for harsh-environment applications. |
| Typical Application | Capacitive sensors, proximity/humidity sensing | Isolation, ADC, and frequency-based signal conversion | Highlights the intended use cases; the parts target different sensing and conversion architectures. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD7740KRMZ | AD7747ARUZ |
|---|---|---|
| Part Status | Active | Active |
| Type | Voltage to Frequency | Capacitance-to-Digital Converter |
| 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 AD7740KRMZ?
The AD7747ARUZ is a 24-bit capacitance-to-digital converter (CDC) with a sigma-delta architecture, designed for high-precision capacitance measurement with a specified resolution of 20 aF and an input capacitance range of ±8 pF. The AD7740KRMZ is a synchronous voltage-to-frequency converter (VFC) that produces an output frequency proportional to an input voltage, with a specified linearity of ±0.1% and a full-scale output frequency range up to 1 MHz. They serve fundamentally different signal-conversion functions and are not functionally interchangeable.
Do the AD7747ARUZ and AD7740KRMZ use the same package and pinout?
No. The AD7747ARUZ is supplied in a 16-lead TSSOP package (RU suffix), while the AD7740KRMZ is supplied in an 8-lead MSOP package (RM suffix). The package body sizes, lead counts, and pin assignments differ, so the PCB land patterns are not compatible and the devices cannot be mounted in the same 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 AD7740KRMZ operates from a single 3.0 V to 5.25 V supply (with a 3.3 V and 5 V specified operation). Designs must ensure the supply rail falls within the respective datasheet-specified range for each part.
What communication interface does each device provide?
The AD7747ARUZ provides a 2-wire I²C-compatible serial interface for reading conversion results and configuring the device. The AD7740KRMZ provides a frequency output (FOUT) whose frequency is proportional to the input voltage, and it does not include a digital serial bus interface. System architecture must account for this difference in host-side interfacing.
Can the AD7747ARUZ and AD7740KRMZ be used in the same application circuit?
No, they are not drop-in replacements. The AD7747ARUZ measures capacitance and outputs digital data over I²C, whereas the AD7740KRMZ converts an analog voltage to a frequency. Because their input signal domains, output formats, packages, and pinouts differ, substituting one for the other requires a complete redesign of the signal chain and PCB layout, not a component swap.
What are the typical target applications for each device?
The AD7747ARUZ is typically used for high-resolution capacitance sensing such as proximity, pressure, and humidity sensing, and precision capacitive sensor interfaces. The AD7740KRMZ is typically used for voltage-to-frequency conversion in isolation, analog-to-digital conversion, and frequency-based signal transmission applications. Application suitability should be confirmed against each datasheet's specified operating conditions.
Are the operating temperature ranges of the two devices the same?
Both the AD7747ARUZ and AD7740KRMZ are specified for the industrial temperature range of −40°C to +105°C. Designers should still verify the exact grade and temperature specification on the specific orderable part number and datasheet revision before committing to a design.