Datasheet

ADP5041 Data Sheet
Rev. 0 | Page 26 of 40
THEORY OF OPERATION
PWM/
PSM
CONTROL
BUCK1
DRIVER
AND
ANTISHOOT
THROUGH
RESET
GENERATOR
DEBOUNCE
VDDA
VDDA
PSM
COMP
LOW
CURRENT
I
LIMIT
ADP5041
VOUT1 FB1 VTHR
ENWD
VIN1
AVIN
SW
PGND
EN1
ENBK
ENLDO1
ENLDO2
MODE
MODE
EN2
EN3
SEL
OPMODE_FUSES
VIN2 FB2 AGND VOUT2 VIN3
ENLDO1
600Ω
ENBK
ENLDO2
600Ω
MR
VDDA
52kΩ
WDI
VOUT3FB3
09652-090
OSCILLATOR
THERMAL
SHUTDOWN
V
REF
WATCHDOG
DETECTOR
nRSTO
VDDA
PWM
COMP
GM ERROR
AMP
85Ω
SOFT START
SYSTEM
UNDERVOLTAGE
LOCK OUT
ENABLE
AND MODE
CONTROL
LDO1
CONTROL
LDO2
CONTROL
Figure 101. Functional Block Diagram
POWER MANAGEMENT UNIT
The ADP5041 is a micro power management unit (micro PMU)
combing one step-down (buck) dc-to-dc regulator, two low
dropout linear regulators (LDOs), and a supervisory circuit, with
watchdog, for processor control. The high switching frequency and
tiny 20-pin LFCSP package allow for a small power management
solution.
The regulators are activated by a logic level high applied to the
respective EN pin. The EN1 pin controls the buck regulator, the
EN2 pin controls LDO1, and the EN3 pin controls LDO2.
Other features available on this device are the MODE pin to
control the buck switching operation and a push-button reset
input.
The regulator output voltages and the reset threshold are set
through external resistor dividers.
When a regulator is turned on, the output voltage ramp is
controlled through a soft start circuit to avoid a large inrush
current due to the discharged output capacitors.
The buck regulator can operate in forced PWM mode if the
MODE pin is at a logic high level. In forced PWM mode, the
switching frequency of the buck is always constant and does not
change with the load current. If the MODE pin is at a logic low
level, the switching regulator operates in auto PWM/PSM mode.
In this mode, the regulator operates at fixed PWM frequency
when the load current is above the power save current threshold.
When the load current falls below the power saving current
threshold, the regulator enters power saving mode, where the
switching occurs in bursts. The burst repetition rate is a
function of the current load and the output capacitor value.
This operating mode reduces the switching and quiescent
current losses.