MCP7940N
Epson alternative: RX8130CE
The MCP7940N is a capable little RTCC and its digital trimming is genuinely useful. What the datasheet asks of you in return is a crystal, two load capacitors and a clean oscillator layout. The comparison covers the MCP7940M as well.
Features of the MCP7940N: two programmable alarms, on-chip digital trimming with ±1 ppm resolution over a ±129 ppm range, power-fail timestamp and battery-backed SRAM.
MCP7940N versus RX8130CE
| MCP7940N — Microchip | RX8130CE — Epson | |
|---|---|---|
| Manufacturer | Microchip | Epson (Seiko Epson) |
| Interface | I²C (400 kHz) | I²C (400 kHz) |
| Crystal integrated | no — external 32.768 kHz crystal plus load capacitors | yes, factory calibrated |
| Accuracy | depends on the crystal used · digital trimming ±1 ppm resolution over ±129 ppm | +5 ±23 ppm at +25 °C (not compensated) |
| Timekeeping current | 925 nA at 3.0 V from the backup cell | 300 nA typ. · 500 nA max. |
| Supply | 1.8 – 5.5 V · backup from 1.3 V | 1.25 – 5.5 V |
| Max. temperature | −40 … +85 °C (industrial grade) | −40 … +85 °C |
| Package | SOIC-8 · TSSOP-8 · PDIP-8 · 2×3 TDFN | CE 3.2 × 2.5 × 1.0 mm · 8.0 mm² footprint |
| Extras | two alarms, 64 byte SRAM, power-fail timestamp | reset output with delay, charge control with full-charge detection, V_IO pin |
What speaks for and against the change
We sell Epson — and we still say where the competitor is better. You would notice it at the first datasheet comparison anyway.
Honestly
- Digital trimming with ±1 ppm resolution over a ±129 ppm range — that is a real tool if you are going to fit your own crystal anyway
- 64 byte battery-backed SRAM and a power-fail timestamp, neither of which the RX8130CE carries
- Available in PDIP, which still helps for repairs and prototypes
The difference
- The crystal is not included. A 32.768 kHz crystal plus its load capacitor matching plus the layout risk of the oscillator loop go on top — Epson delivers one component instead of three
- Current: 300 nA typical against 925 nA. Roughly a third, and that ratio decides how long a backup cell lasts
- Supply from 1.25 V against 1.8 V
- Trimming corrects a static offset at one temperature. It does not follow the crystal's drift across the range — where that matters, the RX8901CE holds ±3.0 ppm from −40 to +85 °C
- Reset output with a selectable delay, charge control with full-charge detection and a separate V_IO pin
Frequently asked questions
What is the Epson alternative to the MCP7940N?
The RX8130CE is the closest match on function and supply range, with the RX8901CE where the clock has to stay accurate over temperature. Neither is a drop-in: package, pinout and register map differ.
Does the MCP7940N need an external crystal?
Yes. Microchip specifies a 32.768 kHz tuning fork crystal with external load capacitors. The accuracy then depends on that crystal, on how well its load capacitance is matched and on the oscillator layout. The Epson modules carry the calibrated crystal inside the package.
Is the MCP7940N's digital trimming as good as temperature compensation?
No. Trimming corrects a fixed offset — you measure the deviation once and dial it out. A DTCXO like the RX8901CE measures temperature continuously and corrects the drift as it happens, which is what keeps ±3.0 ppm valid from −40 to +85 °C.
Who supplies an alternative to the MCP7940N in Europe?
Timing Devices Europe in Ladenburg near Heidelberg, Germany stocks the complete Epson RTC programme in its own warehouse — physically on site, not at the manufacturer. Samples, comparison and series demand in one go, answered the same working day.
Samples and a comparison for the MCP7940N.
Tell us which version you use today, together with quantity and date. We will put together the Epson equivalent with its datasheet and the migration effort — from our own warehouse in Ladenburg near Heidelberg, Germany.