Datasheet

Data Sheet ADP5037
Rev. D | Page 15 of 28
THEORY OF OPERATION
LDO
CONTROL
LDO
UNDERVOLTAGE
LOCKOUT
SOFT START
PWM/
PSM
CONTROL
BUCK2
DRIVER
AND
ANTISHOOT
THROUGH
SOFT START
DRIVER
AND
ANTISHOOT
THROUGH
OSCILLATOR
THERMAL
SHUTDOWN
SYSTEM
UNDERVOLTAGE
LOCKOUT
PWM
COMP
GM ERROR
AMP
GM ERROR
AMP
PSM
COMP
PSM
COMP
LOW
CURRENT
I
LIMIT
PWM
COMP
LOW
CURRENT
I
LIMIT
R1
R2
ADP5037
V
OUT1
V
OUT2
VIN1
AVIN
SW1
PGND1
VIN3 AGND VOUT3
FB3
PGND2
SW2
VIN2
AVIN
75Ω
ENBK1
ENABLE
AND
MODE
CONTROL
EN1 ENBK1
ENBK2
ENLDO1
ENLDO2
600Ω
ENLDO2
75Ω
ENBK2
EN2
EN3
EN4
600Ω
ENLD O 1
LDO
CONTROL
LDO
UNDERVOLTAGE
LOCKOUT
R3
R4
VIN4
VOUT4
AVIN
FB4
B
SEL
OP
MODE
MODE2
A
Y
MODE
FB1 FB2
PWM/
PSM
CONTROL
BUCK1
09887-005
Figure 45. Functional Block Diagram
POWER MANAGEMENT UNIT
The ADP5037 is a micropower management units (micro PMU)
combining two step-down (buck) dc-to-dc convertors and
two low dropout linear regulators (LDOs). The high switching
frequency and tiny 24-lead LFCSP package allow for a small
power management solution.
To combine these high performance regulators into the micro
PMU, there is a system controller allowing them to operate
together.
The buck regulators can operate in forced PWM mode if the
MODE pin is at a logic high level. In forced PWM mode, the
buck switching frequency is always constant and does not
change with the load current. If the MODE pin is at logic low
level, the switching regulators operate in auto PWM/PSM
mode. In this mode, the regulators operate at fixed PWM
frequency when the load current is above the PSM current
threshold. When the load current falls below the PSM current
threshold, the regulator in question enters PSM, 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. The auto PWM/PSM mode transition is controlled
independently for each buck regulator. The two bucks operate
synchronized to each other.
The ADP5037 has individual enable pins (EN1 to EN4) control-
ling the activation of each regulator. The regulators are activated
by a logic level high applied to the respective EN pin. EN1 controls
BUCK1, EN2 controls BUCK2, EN3 controls LDO1, and EN4
controls LDO2.
Regulator output voltages are set through external resistor
dividers or can be optionally factory programmed to default
values (see the Ordering Guide section).
When a regulator is turned on, the output voltage ramp rate is
controlled though a soft start circuit to avoid a large inrush
current due to the charging of the output capacitors.