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Data Sheet

ADP5003

Rev. A | Page 17 of 31

Current-Limit and Short-Circuit Protection

The buck regulator includes current-limit protection circuitry

to limit the amount of forward current through the field effect

transistor (FET) switches. When the valley inductor current

exceeds the overcurrent limit threshold for a number of clock

cycles during an overload or short-circuit condition, the

regulator enters hiccup mode. The regulator stops switching

and then restarts with a new soft start cycle after the hiccup

time, tHICCUP, and repeats until the over-current condition is

removed. If the buck regulator output voltage falls below 50%

of the nominal output voltage, the regulator immediately enters

hiccup mode. When the valley inductor current falls below the

negative current-limit threshold, the NFET turns off and the

PFET remains off allowing the inductor current to be discharged

via the PFET body diode. The PFET turns on again with the

next clock edge after the inductor current no longer exceeds

the negative current-limit threshold.

A CH2

1.08V

CH1 10.0V

CH2 2.00V

20.0ms

79.7600ms

CH3 2.0A

VVOUT1

VSW1

tHICCUP

3.5A

Figure 40. Short-Circuit Response (Current Limit and Hiccup Mode)

LDO REGULATOR

The ADP5003 contains a single low noise, low dropout (LDO)

linear regulator that uses an NFET pass device to provide high

PSRR with low headroom voltage and an output current up to 3A.

The LDO regulator can operate with an input voltage of 0.65 V

to 5 V while providing excellent line and load transient response

using 10 µF ceramic input and output capacitors.

LDO Startup

The LDO regulator turns on with a controlled soft start ramp to

limit inrush current. This soft start ramp is dictated by tSSLDO,

which is typically 400 µs.

–4.5

–3.5

–2.5

–1.5

–0.5

0.5

1.5

2.5

3.5

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

–0.4

–0.2

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

TIME (ms)

0.1A

VEN2

Figure 41. LDO Startup

Current Limit

The LDO operates in current limit when the output load exceeds

ILIMIT2. When in current limit operation, the output voltage

reduces to maintain a constant output current.

Differential Remote Sensing

The LDO can sense at the point of load by using VFB2P and

VFB2N as shown in Figure 42. Differential remote sensing

compensates for both the source drop and the return drop to

provide a more precise supply scheme at the point of load.

AGND1

PVOUT2

VFB2P

LOW NOISE

LDO ACTIVE

FILTER

LOAD

–

VFB2N

AGND2

Figure 42. Differential Remote Sensing

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