LTC3203_15 Datasheet, PDF (9/16 Pages) Linear Technology – 500mA Output Current Low Noise Dual Mode Step-Up Charge Pumps

LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
OPERATIO
When the output voltage drops enough to overcome the
burst comparator hysteresis, the part wakes up and com-
mences normal fixed frequency operation. The output
capacitor recharges and causes the part to re-enter the
Sleep state if the output load still remains less than the
Burst Mode threshold. This Burst Mode threshold varies
with V_IN, V_OUT and the choice of output storage capacitor.
Short-Circuit/Thermal Protection
The LTC3203/LTC3203-1/LTC3203B/LTC3203B-1 have
built-in short-circuit current limit as well as over-tempera-
ture protection. During a short-circuit condition, the chip
will automatically limit the output current to approximately
1A. At higher temperatures, or if the input voltage is high
enough to cause excessive self-heating of the part, the
thermal shutdown circuitry will shut down the charge
pump once the junction temperature exceeds approxi-
mately 150°C. It will enable the charge pump once the
junction temperature drops back to approximately 135°C.
The LTC3203/LTC3203-1/LTC3203B/LTC3203B-1 will
cycle in and out of thermal shutdown indefinitely without
latch-up or damage until the short circuit condition on
V_OUT is removed.
Soft-Start
To prevent excessive current flow at V_IN during start-up,
the LTC3203/LTC3203-1/LTC3203B/LTC3203B-1 have
built-in soft-start circuitry. Soft-start is achieved by in-
creasing the amount of current available to the output
charge storage capacitor linearly over a period of approxi-
mately 250µs.
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