SH3100 Datasheet, PDF (14/80 Pages) Semtech Corporation – Supervisory IC with I2C Interface and PWM

POWER MANAGEMENT
Application Diagrams - Modes 4 to 6
Mode 4 – Bootstrap boost regulation using
internal switching FET
VDD is stepped up from external supply source
using internal switching on PWM.
Starts up with external supply as low as 1.8 V and
continue to operate as external supply drops as low
as 1 V.
Regulation timing for all switching regulator modes
is set by internal programmable HFDCO oscillator.
Register settings
DeviceMode = 001
ComparatorSource = 00 (VDD)
CLK1HF/LF = 1
ForcedDACValue = xx (to set VDD level)
Set CLK1 frequency as desired
Mode 5 – Bootstrap boost regulation using
external switching FET.
VDD is stepped up from external supply source
using external switching FET controlled by PWM.
Use for higher load requirements.
Regulated output voltage is set by internal DAC8.
Feedback is fixed as VDD/3.
1Mohm pull-down resistor is required to indicate
external switching configuration to SH3100.
Register settings
DeviceMode = 001
ComparatorSource = 00 (VDD)
CLK1HF/LF = 1
ForcedDACValue = xx (to set VDD level)
Set CLK1 frequency as desired
Mode 6 – Normal boost regulation using external
FET & external feedback divider
Regulated supply is stepped up from VDD using
external switching FET controlled by PWM.
Regulated output voltage is set by internal DAC8
and feedback on SNSE.
1Mohm resistor indicates external switching and
also ensures NMOS is turned off during power up
Register settings
DeviceMode = 001
ComparatorSource = 11 (SNSE)
CLK1HF/LF = 1
ForcedDACValue = xx (to set VDD level)
Set CLK1 frequency as desired
© 2006 Semtech Corp.
14
SH3100
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