SH3100 Datasheet, PDF (11/80 Pages) Semtech Corporation – Supervisory IC with I2C Interface and PWM

SH3100
POWER MANAGEMENT
Operating Modes
The SH3100 is fuse programmed to a default power-up operating mode from a number of possible options. Once
the device has been initialized, it is possible to use the I²C interface to change between any of the following available
modes.
Mode
1
2
3
4
5
6
LDO
NO
YES
NO
NO
NO
NO
Switching Fan
Reset
Regulator Control Duration
Notes
Standard operating mode. PWM pin may be used as general-
purpose PWM/PDM output. INT defaults to high impedance
NO
NO
YES and may then be programmed by I²C access to define an
Interrupt function or GPIO as required. Start-up frequency is
determined by configuration fuse setting
LDO is enabled on PWM pin with default output voltage
NO
NO
NO between 3V and 4.5V as set by fuses. Setting may then be
overridden by I²C access
NO
YES
NO
Automatic fan control is enabled with SNSE input used to
detect fan rotation and PWM pin used for fan drive
Bootstrap boost regulation from an external supply to VDD
with internal switching FET and transfer diode on PWM pin.
Regulator feedback is determined by the internal VDD divider.
The PWM pin is active low during the inductor energize period
and floating during the transfer period (to allow current to flow
YES
NO
NO
from PWM to VDD through the internal diode). During power
up, the PWM pad is clamped to VDD to ensure that the chip
can start up with an input battery supply as low as 1.8V.
Conversion efficiency is very low due to the relatively high
internal switching FET and diode impedances, so this mode is
recommended only for powering the SH3100 alone and where
energy efficiency is not important
Bootstrap boost regulation from an external supply to VDD
with external switching FET and transfer diode. Regulator
feedback is determined by the internal VDD divider. This is
suitable for heavier load requirements and is limited by the
YES
NO
NO capabilities of the external components. The PWM pin drives
an external NMOS or NPN switching the inductor to GND, and
is High during the inductor energize period and Low during the
transfer period (to allow current to flow through the external
diode)
Normal boost regulation from VDD to a separate supply
with external switching FET and transfer diode. Regulator
YES
NO
NO
feedback is input on the SNSE pin. The PWM pin drives an
external NMOS or NPN switching the inductor to GND, and is
High during the inductor energize period and Low during the
transfer period
Note: The Reset Duration column refers to the option to select Low, Medium or fuse set reset durations by the tristate
input SNSE pin. If this option is not available then the reset duration defaults to the fuse setting.
© 2006 Semtech Corp.
11
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