ADP5037 Analog Devices, ADP5037 Datasheet - Page 20

• Manufacturer Part Number: ADP5037
• Description: Dual 3 MHz, 800 mA Buck Regulators with Two 300 mA LDOs
• Manufacturer: Analog Devices

ADP5037
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-Downs
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 LDOs and 75 Ω for the
bucks. Figure 46 shows the activation timings for the active
pull-downs during regulator activation and deactivation.
LDO1 AND LDO2
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.
Each LDO operates with an input voltage of 1.7 V to 5.5 V. The
wide operating range makes these LDOs suitable for cascading
configurations where the LDO supply voltage is provided from
one of the buck regulators.
ADP5037
contains two LDOs with low quiescent current
Rev. A | Page 20 of 28
Each LDO output voltage is set through external resistor
dividers as shown in Figure 48 for LDO1. 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 LDOs also provide 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.
LDO1 is optimized to supply analog circuits because it offers
better noise performance compared to LDO2. LDO1 should be
used in applications where noise performance is critical.
VIN3
V
OUT3
Figure 48. LDO1 External Output Voltage Setting
= V
FB3
LDO1
Rb
Ra
+ 1
VOUT3
FB3
Ra
Rb
C7
1µF
Data Sheet
VOUT3