ADCS7478AIMFX - 8-Bit 1MSPS SAR ADC, SOT-23-6 | Texas Instruments
MPN: ADCS7478AIMFX ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.95 | $1.95 |
| 10 | $1.78 | $17.80 |
| 100 | $1.52 | $152.00 |
| 500 | $1.31 | $655.00 |
| 1,000 | $1.14 | $1,140.00 |
| 3,000 | $0.98 | $2,940.00 |
ADCS7478AIMFX Overview
A SAR ADC is a successive-approximation analog-to-digital converter: it performs a binary search through an internal capacitive DAC to converge on the input voltage in N conversion cycles, where N is the resolution in bits. Compared with delta-sigma or pipeline ADCs, SAR converters offer deterministic latency, no pipeline delay, and excellent dynamic performance at moderate sample rates, which makes them the workhorse for multiplexed data acquisition, motor control, and instrumentation front-ends.
The ADCS7478 uses the supply pin itself as the conversion reference, eliminating an external reference and supporting the smallest possible footprint for cost- and space-constrained designs. The serial interface is compatible with SPI, QSPI, and MICROWIRE hosts, allowing direct connection to most microcontrollers and DSPs without glue logic. The device also offers a power-down pin to minimize supply current between conversions.
Architecturally, the ADCS747x family is a CMOS SAR core with internal track-and-hold, scaled to deliver 1 MSPS throughput at low power dissipation. The ADCS7478 is the 8-bit resolution member of the family; the ADCS7476 (12-bit) and ADCS7477 (10-bit) share the same SOT-23-6 pinout, allowing designers to migrate resolution without changing PCB layout.
Typical applications include portable instrumentation, isolated data acquisition, optical modules, and consumer electronics where a small-footprint ADC with digital-friendly serial output is needed. Battery-powered sensor readouts benefit from the integrated power-down mode between samples.
When designing with the ADCS7478, add 0.1 µF decoupling close to the supply pin and keep the analog input trace short to minimize coupling from the serial clock. Note that using VDD as the reference couples digital noise into conversions; for higher-precision requirements, use an external ADC with a dedicated reference.
This page synthesizes verified distributor pricing, drop-in alternatives including the TI /NOPB lead-free variant and the ADCS7478AIMFE extended-temperature option, and practical design notes that go beyond the manufacturer datasheet.
Drop-in alternatives for ADCS7478AIMFX — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with ADCS7478AIMFX (same form factor and footprint) — differing in Package, Resolution, Input Type, Sampling Rate, Operating Temperature Range.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ADCS7478AIMFX/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
ADCS7478AIMFE
✅ Drop-In✓ In Stock
$4.4267 / Unit
View Datasheet →ADCS7478AIMF
✅ Drop-In✓ In Stock
$2 / Unit
View Datasheet →AD7478ARTZ-REEL7
✅ Drop-In📋 Reference alternative (not in catalog)
ADCS7477AIMFX
✅ Drop-In📋 Reference alternative (not in catalog)
ADCS7478AIMFX Maximum Ratings & Electrical Characteristics
| Resolution | 8 bit |
| Sample Rate | 1 MSPS |
| Number of Channels | 1 |
| Architecture | SAR (Successive Approximation Register) |
| Input Type | Single-Ended |
| Data Interface | MICROWIRE, QSPI, Serial, SPI |
| Supply Voltage Range | 2.7 V to 5.25 V |
| Reference Type | Supply (VDD used as reference) |
| Operating Temperature Range | -40 °C to +85 °C |
| Package / Case | SOT-23-6 |
| Supplier Device Package | SOT-23-6 |
| Mounting Type | Surface Mount |
| Packaging | Tape & Reel |
| RoHS Status | Compliant |
| Lead-Free Option (NOPB) | Yes (separate ordering code) |
ADCS7478AIMFX Pin Configuration
| Pin 1 | VIN — Analog input (single-ended) |
| Pin 2 | GND — Ground |
| Pin 3 | VDD — Supply voltage; also used as conversion reference |
| Pin 4 | DOUT — Serial data output (SPI/MICROWIRE/QSPI) |
| Pin 5 | SCLK — Serial clock input |
| Pin 6 | CS/PD — Chip select (active low) and power-down control |
Typical Applications
ADCS7478AIMFX is suitable for 7 applications: Portable Instrumentation and Battery-Powered Sensor Readout, Optical Module Monitoring (Laser Bias / Photodiode Current), Isolated Data Acquisition Front-End, Consumer Audio and Display Control Loops, Touch and Proximity Sensing Digitization, Motor Control Position-Feedback Path, General-Purpose 8-Bit System Monitoring.
Portable Instrumentation and Battery-Powered Sensor Readout
The ADCS7478AIMFX fits portable instrumentation because its 1 MSPS SAR throughput, 6-pin SOT-23 footprint, and integrated power-down pin let it sit on a tiny battery-powered PCB while still capturing fast sensor transients. With 8-bit resolution and VDD-as-reference, the part delivers enough accuracy for thermistor, battery-monitor, and strain-gauge readouts where 1 LSB corresponds to well below 1% of full scale. Placing the ADC adjacent to the sensor minimizes analog trace noise, and the SPI-compatible serial output streams directly into a low-power microcontroller without glue logic.
Recommended
Optical Module Monitoring (Laser Bias / Photodiode Current)
Optical transceiver modules use the ADCS7478AIMFX to digitize laser-bias and photodiode-monitoring currents at 1 MSPS while occupying minimal board area. The SAR architecture provides deterministic single-cycle latency, which matters for closed-loop laser-power control where pipeline delay would destabilize the loop. The SOT-23-6 footprint fits inside QSFP, SFP, and PON optical modules where PCB real estate is at a premium. The supply-as-reference simplifies BOM by eliminating an external reference component.
Recommended
Isolated Data Acquisition Front-End
Industrial isolated data-acquisition front-ends place the ADCS7478AIMFX on the field side of a digital isolator, where its 1 MSPS throughput and SPI/MICROWIRE-compatible serial output drive a low-cost digital isolator cleanly. Because the serial interface is a unidirectional SCLK/DOUT pair plus chip-select, isolation can be implemented with 3-channel isolators and minimal propagation-delay budget. The 2.7 V to 5.25 V supply lets the ADC run directly from the same rail that powers the field-side isolator, simplifying the isolated power architecture.
Recommended
Consumer Audio and Display Control Loops
Consumer audio and display products use the ADCS7478AIMFX to read back potentiometer wiper voltages, backlight sense currents, and rotary-encoder analog outputs at 1 MSPS. The 8-bit resolution is sufficient for backlight dimming curves, volume tap-detection, and touch-screen reference readouts where human-perceptible steps are at least 1% of full scale. The SOT-23-6 package allows the ADC to sit near the analog source on densely packed consumer boards, reducing ground-bounce coupling into the conversion.
Recommended
Touch and Proximity Sensing Digitization
Capacitive touch and proximity-sensing front-ends digitize the analog sense waveform with the ADCS7478AIMFX, leveraging its 1 MSPS sample rate to capture multiple points per sensing cycle for noise averaging. The single-ended analog input accepts the rectified sense voltage directly, and the SPI-compatible output streams samples into the touch controller. Its 6-pin SOT-23 footprint allows the ADC to sit adjacent to the touch electrode, minimizing parasitic pickup on the analog trace.
Recommended
Motor Control Position-Feedback Path
BLDC and stepper motor control loops use the ADCS7478AIMFX to digitize Hall-sensor or resolver-derived analog position signals at 1 MSPS, providing deterministic SAR latency that aligns with PWM switching periods. The 8-bit resolution is sufficient for coarse commutation feedback where each step spans several electrical degrees. The SPI serial output is compatible with most digital-motor-control MCUs and DSPs, simplifying firmware development across motor platforms.
Recommended
General-Purpose 8-Bit System Monitoring
The ADCS7478AIMFX is a workhorse for general-purpose 8-bit system monitoring: supply-rail health, temperature-sensor outputs, and current-sense amplifier signals can all be digitized with one tiny IC. The integrated power-down pin allows the host MCU to duty-cycle conversions, reducing average supply current to a few microamps in standby. Designers standardize on this part for new 8-bit ADC sockets because the supply-as-reference architecture and small footprint remove external reference cost and area.
Recommended
Recommended Products Summary
Engineering reference data for ADCS7478AIMFX — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ADCS7478AIMFX/NOPB | ADCS7478AIMFE | ADCS7478AIMF | AD7478ARTZ-REEL7 | ADCS7477AIMFX |
|---|---|---|---|---|---|---|
| Package | SOT-23-6 | SOT-23-6 - same | SOT-23-6 - same | SOT-23-6 - same | SOT-23-6 - same | SOT-23-6 - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Analog Devices | Texas Instruments |
| Resolution | 8 bit | 8 bit | 8 bit | 8 bit | 8 bit | 10 bit |
| Sample Rate | 1 MSPS | 1 MSPS | 1 MSPS | 1 MSPS | 1 MSPS | 1 MSPS |
| Supply Voltage | 2.7 V to 5.25 V | 2.7 V to 5.25 V | 2.7 V to 5.25 V | 2.7 V to 5.25 V | 2.7 V to 5.25 V | 2.7 V to 5.25 V |
| Reference Type | Supply (VDD) | Supply (VDD) | Supply (VDD) | Supply (VDD) | External VREF | Supply (VDD) |
| Operating Temperature | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +125 °C | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C |
| Lead-Free / RoHS | Yes (standard RoHS, separate /NOPB code) | Yes (explicit Pb-free code) | Yes | Yes | Yes | Yes |
Key Differentiators
- Supply-as-reference eliminates external reference BOM (vs AD7478ARTZ-REEL7)
- Pin-compatible 8/10/12-bit resolution upgrade path (vs ADCS7477AIMFX (10-bit) and ADCS7476AIMFX (12-bit))
- Lower-cost and more available than legacy AD7478 (vs AD7478ARTZ-REEL7)
Design Notes
Decouple VDD (pin 3) with a 0.1 µF X7R ceramic capacitor placed within 2 mm of the pin. The ADCS7478 uses VDD as the conversion reference, so any supply ripple couples directly into the LSB; a clean, low-ESR rail is essential for accurate conversions. Add a 10 µF bulk capacitor if the source impedance of the 3.3 V or 5 V rail is non-trivial, and avoid sharing the ADC's VDD pin with high-current digital loads.
Route the analog input (VIN, pin 1) as a short, guarded trace away from the SCLK and DOUT lines to minimize digital-to-analog crosstalk. Place a small RC low-pass filter (e.g., 100 Ω and 10 pF) at VIN if the source impedance exceeds 50 Ω, since the ADC's input bandwidth interacts with the source network. The SOT-23-6 thermal pad is not present on this part; standard SOT-23-6 land pattern from the TI ADCS7478 datasheet package drawing is sufficient.
Keep SCLK below the maximum rated frequency and ensure CS/PD transitions do not occur near the SCLK active edge to avoid glitches in DOUT. The SAR architecture guarantees single-cycle conversion latency, so jitter on SCLK directly modulates aperture timing; use a clean MCU-generated clock rather than a divided noisy source. If the host MCU has long interrupt latency, gate SCLK with a timer rather than bit-banging to maintain timing integrity.
Do not assume the ADCS7478AIMFX and the legacy AD7478 are bit-identical: the AD7478 uses an external reference while the ADCS7478 uses VDD-as-reference, which slightly changes noise coupling. Power-down via CS/PD lowers supply current dramatically, but the host must allow the wake-up time before issuing the next SCLK burst. Finally, do not exceed 5.25 V on VDD; the absolute-maximum rating is 6 V, but operation above 5.25 V violates the datasheet specification.
Compliance Information
Standard ADCS7478AIMFX is RoHS-compliant; the ADCS7478AIMFX/NOPB suffix is the explicit Pb-free ordering code per TI ordering information. AEC-Q100 not applicable for the standard part - use ADCS7478AIMFE for extended automotive temperature range.