SH3100IMTR SEMTECH [Semtech Corporation], SH3100IMTR Datasheet - Page 9

• Manufacturer Part Number: SH3100IMTR
• Description: Supervisory IC with I2C Interface and PWM
• Manufacturer: SEMTECH [Semtech Corporation]

The main power supply is between VDD and GND and may
have any value between 1.7V and 5.5V for normal opera-
tion. In order to guarantee start-up, VDD should initially be
taken to at least 100mV above the reset threshold (VBO)
in order to overcome the reset threshold hysteresis; e.g.,
for a VBO level of 2.8V, VDD must initially rise to at least
2.9V for the chip to come out of reset.
The battery backup supply is between VBAK and GND. The
SH3100 switches to VBAK, if VDD drops below VBO and
VBAK is within its valid operating range of 0.9V to 5.5V for
battery backup.
While VBAK is within its valid operating range during bat-
tery backup, RTC operation is maintained and those reg-
ister contents not reset by a VBO reset event (Brownout)
are maintained. Any functions not required during battery
backup are shut down to save power.
© 2006 Semtech Corp.
POWER MANAGEMENT
Power Supplies & Battery Backup
Note: If the 32.768kHz system clock output is enabled on
CLK1 during battery backup then the maximum VBAK voltage
for valid CLK1 output is 4.5V. Battery backup continues for
VBAK voltages above 4.5V, but the CLK1 output is no longer
guaranteed to function correctly.
9
When running in battery backup from the 32.768kHz
crystal oscillator, full RTC accuracy is maintained down to
the minimum VBAK of 0.9V.
When running in battery backup from the internal
32.768kHz oscillator, RTC accuracy is maintained only
down to a VBAK level of 1.7V. Below this point, operation
continues down to 0.9V, but a fl ag is set to indicate that
the internal oscillator can no longer be guaranteed to be
within ±3% of 32.768kHz.
The minimum VBAK level is guaranteed as 0.9V; however,
depending on process variations, operation may continue
down to 0.7V before battery back up fails.
An unpowered (cold) chip starts up and initializes only
when VDD is applied. Applying only VBAK to a cold chip
does not cause it to start up.
Battery backup facility is only enabled once the chip has
come out of reset after an initial power-up.
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SH3100