EM1537- Timing & Clock Circuits

Low Power 32kHz Circuit for Analog Quartz Watches - Ultra-Low Power

General Description

The EM1537 is an integrated circuit in a low power CMOS technology for battery operated wristwatches with bipolar stepping motors. Time base is a 32 kHz crystal oscillator. It has a very low current consumption of typ. 100 nA in a wide voltage range of 1.2 to 3.6 Volt.

The IC is available in two voltage ranges - 1.2 to 1.8 Volt and 1.8 to 3.6 V.

Motor pulse width is programmable from 0.098 ms to 14.65 ms in steps of 0.98 ms by metal mask. Motor period is programmable from 2 x 1s to 2 x 60 s in steps of 1 s selectable by metal mask. Motor pulse chopping is programmable from 1/8 to 8/8 in steps of 1/8 with chopping frequencies of 1024 Hz or 2048 Hz selectable by metal mask. Motor period in Motor test mode is selectable 2 x 31.25 ms or 2 x 62.5 ms by metal mask.

Input and output capacitors are integrated on chip and also programmable by metal mask.

With a fully debounced RESET pad, the motor can be stopped.

A multi-functional bi-directional pad MTEST acts as output for a 32 Hz or 512 Hz for frequency tuning - if open, or – if connected to Vp – accelerates the motor period by a factor of 16 or 32.


  • Analog watches
  • Driver for bipolar stepping motors

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  • Low power 32 kHz Quartz oscillator
  • Operating voltage ranges 1.55V and 3 Volt.
  • Very low current consumption typ. 100 nA at 1.5V.
  • Motor pulse width motor period and motor pulse chopping is programmable in a wide range by metal mask and do not require additional bonds.
  • Fully debounced RESET input for accurate time setting and power saving during shelf life.
  • Integrated capacitors, mask selectable is steps of 1 pF up to 35 pF.
  • Operation temperature range: -10°C to +60°C
  • Available in chip form, SO8 package
EM1537 Data Sheet233 KB