SC633



optimum transient performance, when the input voltage

reaches the mode transition thresholds.

Protection Circuitry

The SC633 also provides protection circuitry that prevents

the device from operating in an unspecified state. These

functions include:

Over-Current Protection (OCP)

Short-Circuit Current Protection (SCCP)

Over-Temperature Protection (OTP)

Over-Current Protection

Over-current protection is provided to limit the output

current. When V

to A typical. The threshold at 2V allows the device to

recover from excessive voltage droop during an over

current.

Short-Circuit Current Protection

Short-circuit current protection is provided to limit the

current that can be sourced when the output is shorted to

ground. When a short circuit forces V

the SCCP detects the condition and limits the output

current to 600mA (typical).

Over-Temperature Protection

The over-temperature circuit helps prevent the device

from overheating and experiencing a catastrophic failure.

When the junction temperature exceeds 65°C, the device

is disabled. It remains disabled until the junction tempera-

ture drops below this threshold. Hysteresis is included

•

•

•

Applications Information (continued)

that prevents the device from re-enabling until the junc-

tion temperature is reduced by 20°C.

Capacitor Selection

The SC633 is designed to use low-ESR ceramic capacitors

for the input and output bypass capacitors as well as the

charge pump bucket capacitors. Ideal performance is

achieved when the bucket capacitors are exactly equal.

The value of input and output decoupling capacitors will

vary with system requirements. For best ripple perfor-

mance C

capacitors C

0µF capacitors may be used in place of each 22µF.

When selecting capacitors for an application, first consider

the DC voltage characteristic of the capacitor. The value

of capacitance at the DC operating voltage may be con-

siderably lower than the rated value. The following table

lists recommended capacitor values which have been

chosen to minimize the impact of this limitation.

Table 1 — Recommended Capacitors

Capacitor Value

μF

Case

Size

Notes

C

22

0805

Typical output V

charge pump modes

Typical input ripple ≤ 00mV in all

charge pump modes

C

BUCKET

2.2

0603

Required for the full rated output

current

C

BUCKET

2.2

0402

Useful for load current up to

300mA

NOTE: Use only X5R type capacitors, with a 6.3V rating or higher

The highest capacitance values in the smallest package

sizes will tend to have poor DC voltage characteristics.

The highest value 0402 size capacitor retains as little as

35% of its rated value at 5VDC. The same value chosen in

the next larger package size, 0603, will retain about 60%

of its rated value at 5VDC.