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-REEL7 are not functionally interchangeable. The AD7747ARUZ is a 24-bit capacitance-to-digital converter with a differential capacitance input, I2C interface, and integrated temperature sensor, while the AD7740KRM-REEL7 is a 16-bit voltage-to-frequency converter with a single-ended voltage input and no digital interface. Their differing conversion architecture, input signal type, output format, and package footprint make direct substitution impractical without redesign.
Different conversion architecture
Different input signal type
Different output interface
Different package footprint
Parts at a glance
Part B
AD7740KRM-REEL7
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 7763 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-REEL7 | Why it matters |
|---|---|---|---|
| Resolution | 24-bit (Capacitance to Digital Converter) | 16-bit (Voltage to Frequency Converter) | Resolution determines the smallest measurable change; the AD7747 offers higher resolution for precision capacitance sensing, while the AD7740 targets frequency-based voltage conversion. |
| Measurement Type | Capacitance-to-digital (CDC) | Voltage-to-frequency (VFC) | The core function differs fundamentally; these parts are not functionally substitutable because one measures capacitance and the other converts voltage to frequency. |
| Input Type | Differential capacitance input | Single-ended voltage input | Input topology dictates sensor compatibility; the AD7747 suits differential capacitive sensors, while the AD7740 suits single-ended analog voltage signals. |
| Output Interface | I2C digital interface | Frequency output (pulse train) | The output format determines how the host system reads data; I2C requires a digital bus, whereas the AD7740 outputs a frequency that must be counted. |
| Supply Voltage | 2.7 V to 5.25 V | 3.0 V to 5.25 V (single supply) | Supply range affects compatibility with system rails; the AD7747 supports slightly lower minimum voltage, which can matter in low-voltage designs. |
| Package | 16-lead TSSOP | 8-lead MSOP | Package footprint and pin count affect PCB layout and cannot be swapped without board redesign. |
| Operating Temperature Range | -40°C to +125°C | -40°C to +85°C | Temperature range determines suitability for harsh environments; the AD7747 supports higher ambient temperatures. |
| Typical Application | Precision capacitive sensing (pressure, humidity, position) | Isolation, signal conditioning, voltage monitoring | Intended applications differ, confirming these parts serve distinct roles and are not drop-in replacements for each other. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD7747ARUZ | AD7740KRM-REEL7 |
|---|---|---|
| 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-REEL7?
The AD7747ARUZ is a 24-bit capacitance-to-digital converter (CDC) with a sigma-delta architecture, designed for high-resolution capacitance measurement (up to ±8 pF with 21-bit effective resolution). The AD7740KRM-REEL7 is a synchronous voltage-to-frequency converter (VFC) that produces an output frequency proportional to an input voltage. They serve fundamentally different signal-chain roles: capacitance sensing versus voltage-to-frequency conversion.
Are the AD7747ARUZ and AD7740KRM-REEL7 pin-compatible or package-compatible?
No. The AD7747ARUZ is supplied in a 16-lead TSSOP package, while the AD7740KRM-REEL7 is supplied in an 8-lead MSOP package. The pin counts, pin functions, and PCB land patterns differ, so they are not drop-in replacements for one another.
What are the supply voltage and interface differences between these two parts?
The AD7747ARUZ operates from a 2.7 V to 5.25 V supply and communicates via an I²C-compatible serial interface. The AD7740KRM-REEL7 operates from a 3.0 V to 5.25 V supply (with a 2.5 V reference option) and provides a digital frequency output; it does not use a serial bus interface. Designers must account for these supply and interface differences when comparing the two.
Can the AD7747ARUZ be used to replace the AD7740KRM-REEL7 in an existing voltage-to-frequency conversion circuit?
No. The AD7747ARUZ is a capacitance-to-digital converter and does not provide a voltage-to-frequency output. Replacing a VFC with a CDC requires redesigning the signal chain, including the sensor interface, output stage, and firmware, and is not a direct substitution.
What are the typical application areas for each device?
The AD7747ARUZ is typically used for high-resolution capacitance sensing such as proximity sensing, level sensing, pressure sensing, and capacitive humidity sensors. The AD7740KRM-REEL7 is typically used for voltage-to-frequency conversion in isolation, analog-to-digital conversion, and frequency-based signal transmission applications.
Do both parts support the same operating temperature range?
Both devices are specified for the industrial temperature range of −40 °C to +85 °C, per their respective manufacturer datasheets. This common range allows both parts to be considered for industrial-grade designs, though their functional roles remain different.
Which part should be selected for a design requiring high-resolution capacitance measurement?
The AD7747ARUZ should be selected, as it is a dedicated 24-bit capacitance-to-digital converter with differential capacitance input and on-chip excitation. The AD7740KRM-REEL7 does not measure capacitance and is not suitable for this function.