MAX1242BCPA - 10-Bit SAR ADC, 73ksps, 8-PDIP | Maxim Integrated
MPN: MAX1242BCPA ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $11.41 | $11.41 |
| 10 | $10.27 | $102.70 |
| 100 | $9.14 | $914.00 |
| 500 | $8.2 | $4,100.00 |
| 1,000 | $7.55 | $7,550.00 |
MAX1242BCPA Overview
A successive-approximation ADC (SAR ADC) is a type of Nyquist-rate data converter that resolves an analog input bit by bit against a precision DAC, comparing each attempt to the unknown voltage and recording the bit pattern that survives. SAR ADCs occupy a middle position in the converter hierarchy: slower than flash ADCs but lower-power and deterministic in latency; faster than integrating ADCs but offer true-snapshot acquisition rather than averaged readings. They are the workhorse of microcontrolled sensing, where a single MCU captures one channel per conversion cycle.
Key features of the MAX1242BCPA include 10-bit resolution with no missing codes, an internal 2.5V reference (the MAX1243 sibling variant accepts an external reference), a single-ended single input channel, hardware- or software-controlled shutdown that drops current to 5uW, and operation from a 2.7V to 5.25V analog supply. The 8-pin footprint (SOIC-8 surface-mount and PDIP-8 through-hole) keeps the device extremely compact for point-of-measurement analog front ends.
Typical applications for the MAX1242BCPA include portable data loggers, pen-digitizer tablets, battery-powered instrumentation, isolated 4-20 mA loop readbacks, and microcontroller-based sensor conditioning boards where a single-channel, low-power ADC is acceptable. The internal reference removes one external component in cost-sensitive designs.
When designing with this part, place the 0.1uF supply bypass capacitor directly on VDD and ensure the SPI lines are routed with controlled impedance to prevent digital switching noise from coupling into the analog input. A power-down command between conversions cuts average current to a few microamps, which is critical for battery-aware designs.
Drop-in alternatives for MAX1242BCPA — 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 MAX1242BCPA (same form factor and footprint) — differing in Conversion Time, Input Type, Package, Sampling Rate, Configuration.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MAX1242BCPA+
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1242BCSA
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
MAX1242BEPA
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1242BCPA+T
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1242BEPA+
✅ Drop-In📋 Reference alternative (not in catalog)
ADS7816P
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1242AEPA+
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
MAX1242BCPA Maximum Ratings & Electrical Characteristics
| Resolution | 10 bit |
| Sampling Rate | 73 ksps |
| Number of Inputs | 1 (single-ended) |
| Input Type | Single-Ended |
| Architecture | SAR (Successive Approximation) |
| Data Interface | SPI / QSPI / MICROWIRE-compatible, 3-wire serial |
| Reference Type | Internal 2.5 V |
| Track-and-Hold | 1.5 us acquisition, integrated |
| Conversion Time | 7.5 us typical |
| Analog Supply Voltage | 2.7 V to 5.25 V single supply |
| Power Dissipation (73 ksps) | 3.7 mW typical |
| Power Dissipation (Power-Down) | 5 uW typical |
| Configuration | S/H + ADC (1:1) |
| Number of A/D Converters | 1 |
| Package | 8-pin PDIP (300 mil) |
| Operating Temperature | 0C to +70C (B temp grade) |
| RoHS Status | Non-compliant (PDIP, contains lead) |
MAX1242BCPA Pin Configuration
| Pin 1 | VDD — +2.7V to +5.25V analog supply |
| Pin 2 | AIN — Analog input (single-ended, 0V to VREF) |
| Pin 3 | GND — Analog ground |
| Pin 4 | REF — Internal 2.5V reference bypass (place 4.7uF cap to GND) |
| Pin 5 | SHDN — Shutdown input, active low (tie high for normal operation) |
| Pin 6 | DOUT — Serial data output (SPI MISO) |
| Pin 7 | CS — Chip select, active low |
| Pin 8 | DIN — Serial clock input (SPI SCLK) |
Typical Applications
MAX1242BCPA is suitable for 7 applications: Portable Battery-Powered Data Logger, Pen Digitizer Tablet, Isolated 4-20 mA Loop Readback, Microcontroller-Based Sensor Conditioning, Audio / Voice Bandwidth Sampling Front End, Handheld Test and Measurement, Automotive Sensor Interface (legacy / aftermarket).
Portable Battery-Powered Data Logger
The MAX1242BCPA's 3.7 mW active power and 5 uW shutdown current make it ideal for battery-powered data loggers powered by coin-cell or Li-ion cells. Its internal 2.5 V reference eliminates the need for a separate reference IC, reducing BOM cost and standby current. The 10-bit resolution is sufficient for slow-changing sensor channels like thermistor voltage dividers, soil moisture sensors, or 4-20 mA loop readbacks. The 73 ksps sampling rate is overkill for low-bandwidth signals, so the host MCU can clock conversions at hundreds of Hz and idle the ADC in shutdown between readings, drawing only microamps of average current.
Recommended
Pen Digitizer Tablet
The MAX1242BCPA is specifically suited for pen-digitizer tablets where its 7.5 us conversion time and 1.5 us acquisition support real-time position sampling. The single-channel single-ended input directly digitizes the pen-tip voltage from the inductive sensor grid. Internal 2.5 V reference simplifies the analog front end by removing a reference IC, while the 3-wire SPI interface connects directly to the tablet's main MCU without glue logic. The 8-pin PDIP footprint supports rapid prototype development and rework on through-hole digitizer test boards.
Recommended
Isolated 4-20 mA Loop Readback
In isolated 4-20 mA current loop receivers, the MAX1242BCPA digitizes the shunt resistor voltage to provide digital telemetry back to the controller side of the isolation barrier. Its 2.7 V to 5.25 V supply range works directly from a 5 V loop supply, while the 73 ksps sampling is more than adequate for process-control update rates (typically 10-100 Hz). The internal 2.5 V reference gives a fixed absolute scale, simplifying calibration routines. The 8-pin PDIP package supports through-hole manufacturing common in industrial termination boards.
Recommended
Microcontroller-Based Sensor Conditioning
For microcontroller-based sensor conditioning boards, the MAX1242BCPA provides a low-component-count analog-to-digital front end that drops directly into any 8-bit or 32-bit MCU with an SPI port. Its 10-bit resolution is sufficient for many sensor types including potentiometer readings, thermistor voltage dividers, and photo-sensor current measurements. The shutdown pin allows the MCU to power down the ADC between conversions, reducing average current dramatically. The internal 2.5 V reference removes one external component compared to the MAX1243 sibling, simplifying the BOM and reducing PCB area.
Recommended
Audio / Voice Bandwidth Sampling Front End
Although the MAX1242BCPA is a 10-bit SAR ADC rather than a dedicated audio codec, its 73 ksps sampling rate covers voice bandwidth (typically 4 kHz Nyquist) comfortably. Designers can use it for low-fidelity voice capture, sound-level meters, or simple voice-activated switches where the 10-bit dynamic range is acceptable. The internal 2.5 V reference provides a stable absolute scale, and the SPI interface easily streams samples to an MCU for tone detection or level metering. The shutdown feature keeps standby current negligible in battery-powered voice triggers.
Recommended
Handheld Test and Measurement
The MAX1242BCPA is well-suited to handheld multimeter and bench-top instrument front ends that need a low-power, low-component-count ADC. Its 2.7 V to 5.25 V supply range works from a single Li-ion cell or USB rail, while its 73 ksps sampling rate easily digitizes DC and low-frequency AC measurements with 10-bit precision. The internal 2.5 V reference removes the cost of an external reference IC. The 8-pin PDIP package simplifies through-hole rework common in prototype instrumentation. The shutdown mode keeps idle current negligible when not actively measuring.
Recommended
Automotive Sensor Interface (legacy / aftermarket)
For automotive aftermarket accessories and non-critical sensor interfaces, the MAX1242BCPA provides an inexpensive, easy-to-interface ADC. Its commercial (B) temperature grade of 0C to +70C limits its use in under-hood applications, but it fits cabin-mounted sensors, OBD-II accessories, and interior telemetry where temperatures stay moderate. The internal 2.5 V reference simplifies analog signal conditioning for potentiometer-based throttle position sensors, fuel level senders, and HVAC controls. Note that for AEC-Q100 qualified designs, the MAX1242AEPA+ automotive-grade variant should be selected instead.
Recommended
Recommended Products Summary
Engineering reference data for MAX1242BCPA — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MAX1242BCPA+ | MAX1242BCSA | MAX1242BEPA | MAX1242BEPA+ | ADS7816P |
|---|---|---|---|---|---|---|
| Package | PDIP-8 (300 mil) | PDIP-8 (300 mil) - same | SOIC-8 - same die, different SMD package | PDIP-8 (300 mil) - same | PDIP-8 (300 mil) - same | PDIP-8 (300 mil) - same |
| Brand | Analog Devices / Maxim Integrated | Analog Devices / Maxim Integrated | Analog Devices / Maxim Integrated | Analog Devices / Maxim Integrated | Analog Devices / Maxim Integrated | Texas Instruments |
| Resolution | 10 bit | 10 bit | 10 bit | 10 bit | 10 bit | 10 bit |
| Sampling Rate | 73 ksps | 73 ksps | 73 ksps | 73 ksps | 73 ksps | 200 ksps |
| Internal Reference | Yes (2.5V) | Yes (2.5V) | Yes (2.5V) | Yes (2.5V) | Yes (2.5V) | No (external reference required) |
| RoHS Compliant | No (SnPb finish) | Yes (lead-free) | No (SnPb finish) | No (SnPb finish) | Yes (lead-free) | No (SnPb finish) |
| Temperature Grade | B (0C to +70C) | B (0C to +70C) | B (0C to +70C) | E (-40C to +85C) | E (-40C to +85C) | 0C to +70C |
| Architecture | SAR (10-bit) | SAR (10-bit) | SAR (10-bit) | SAR (10-bit) | SAR (10-bit) | SAR (10-bit) |
Key Differentiators
- Internal 2.5V reference integrated on-chip (vs ADS7816P (TI))
- 5 uW power-down current consumption (vs ADS7816P (TI))
- Wide 2.7V to 5.25V single-supply operation (vs MAX1243 sibling (external reference))
- Three temperature-grade variants available (vs MAX1242 family siblings (B/E/A))
Design Notes
The MAX1242BCPA consumes 3.7 mW typical at 73 ksps from a 5V supply, and drops to 5 uW in shutdown mode. Drive SHDN high only during the conversion window to minimize battery drain - a typical 100 Hz conversion rate with 1 ms active gives roughly 37 uA average current draw, ideal for coin-cell designs. Decouple VDD with a 0.1 uF ceramic capacitor placed within 5 mm of the VDD pin, plus a 10 uF bulk capacitor at the regulator output.
Place a 4.7 uF bypass capacitor on the REF pin (pin 4) directly to GND to stabilize the internal 2.5 V reference. Route the SPI bus traces (CS, DIN, DOUT) with controlled impedance away from the analog input (AIN, pin 2) and any switching power inductors. Keep the AIN trace short and guarded by a GND fillet on both sides to reduce digital-to-analog coupling. The PDIP-8 through-hole footprint gives ample PCB area for hand-soldered prototype rework.
Do not exceed 5.25 V on VDD - the part has no internal overvoltage protection and will latch up. The AIN input range is 0V to VREF (2.5V with internal reference); driving AIN above VREF saturates the converter and produces a full-scale reading rather than damaging the part, but the result is non-monotonic. Do not leave SHDN floating - tie it high through a 100 kohm pullup or drive it from the MCU GPIO. Failure to bypass the REF pin with 4.7 uF degrades linearity by 1-2 LSB.
The MAX1242BCPA's 1.5 us acquisition time and 7.5 us conversion time define the minimum SPI clock timing. According to the Maxim datasheet, the serial clock DIN must toggle for 14 SCLK cycles per conversion with CS held low. Drive the clock at <3 MHz to meet the acquisition-aperture requirement. Use Schmitt-triggered MCU GPIO for DIN and CS to prevent double-clocking on slow edges; route SCLK and DOUT as a tightly-coupled differential pair on the PCB to reduce ground bounce.
Compliance Information
MAX1242BCPA (SnPb finish) is non-RoHS; the MAX1242BCPA+ suffix denotes the lead-free RoHS-compliant variant per Maxim convention. Commercial (B) temperature grade only - choose MAX1242AEPA+ for AEC-Q100 automotive applications.
