ADP5024 Analog Devices, ADP5024 Datasheet - Page 20

• Manufacturer Part Number: ADP5024
• Description: Dual 3 MHz, 1200 mA Buck Regulators with One 300 mA LDO
• Manufacturer: Analog Devices

ADP5024
desired output voltage. At this limit, the buck transitions to a
mode where the PFET switch stays on 100% of the time. When
the input conditions change again and the required duty cycle
falls, the buck immediately restarts PWM regulation without
allowing overshoot on the output voltage.
Active Pull-Down Resistors
All regulators have optional, factory programmable, active pull-
down resistors discharging the respective output capacitors
when the regulators are disabled. The pull-down resistors are
connected between VOUTx and AGND. Active pull-downs are
disabled when the regulators are turned on. The typical value of
the pull-down resistor is 600 Ω for the LDO and 75 Ω for each
buck. Figure 46 shows the activation timings for the active pull-
downs during regulator activation and deactivation.
LDO
The
and low dropout voltage and provides up to 300 mA of output
current. Drawing a low 10 μA quiescent current (typical) at no
load makes the LDO ideal for battery-operated portable
equipment.
The LDO operates with an input voltage of 1.7 V to 5.5 V. The
wide operating range makes the LDO suitable for cascading
ADP5024
contains one LDO with low quiescent current
Rev. A | Page 20 of 28
configurations where the LDO supply voltage is provided from
one of the buck regulators.
The LDO output voltage is set through external resistor dividers,
as shown in Figure 48. The output voltage can optionally be
factory programmed to default values, as indicated in the Ordering
Guide section. In this event, Ra and Rb are not needed, and FB3
must be connected to the top of the capacitor on VOUT3. FB3 is
0.5 V.
The LDO also provides high power supply rejection ratio
(PSRR), low output noise, and excellent line and load transient
response with only a small 1 µF ceramic input and output
capacitor.
VIN3
V
OUT3
= V
Figure 48. LDO External Output Voltage Setting
FB3
LDO
Ra
Rb
+ 1
VOUT3
FB3
Ra
Rb
Data Sheet
C7
1µF
VOUT3