ADP5034ACPZ-3-R7 datasheet(19/28 Pages) AD

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Data Sheet

ADP5034

Rev. E | Page 19 of 28

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 47 shows the activation timings for the active

pull-downs during regulator activation and deactivation.

LDO1 AND LDO2

The ADP5034 contains two LDOs with low quiescent current

and low dropout linear regulators, 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.

Each LDO output voltage is set through external resistor dividers

as shown in Figure 49 for LDO1. The output voltage can option-

ally 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.

LDO1

FB3

VOUT3

VIN3

1µF

VOUT3 = VFB3

+ 1

Figure 49. LDO1 External Output Voltage Setting

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.

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