R1152N Datasheet, PDF (6/21 Pages) RICOH electronics devices division – High Input Voltage Tolerant Boost Voltage Regulator

R1152N
OPERATION
In these ICs, fluctuation of Output Voltage, VOUT is detected by the feed-back registers, and the result is
compared with a reference voltage with the error amplifier and control the base current of an external PNP
transistor so that a constant voltage is output. The base current is monitored with the base current limit circuit.
If the base current may be too large, the protection circuit works.
TECHNICAL NOTES
When using these ICs, consider the following points:
Make VDD and GND lines sufficient. When their impedance is high, noise pickup or unstable operation may
result.
When you choose an external transistor, select with considering output current, input voltage, and power
dissipation. Generally, low VCE(SAT) and hFE range from 100 to 300 are the appropriate characteristics.
In these ICs, phase compensation is made for securing stable operation even if the load current is varied. For
this purpose, be sure to use a 10µF or more output capacitor, as close as possible to the ICs.
If you choose an electrolytic capacitor, ESR shift by temperature should be small. If you choose a ceramic
capacitor, add an appropriate series resister.
If the set output voltage is less than 4.0V, and IOUT>1A must be obtained, at least VIN≧5.0V is the appropriate
condition. (Supposed as hFE=100)
Voltage level for CE should not be floating, or middle range voltage. If the CE voltage is not appropriate, output
voltage may be unstable or conduction current may flow.
All external components should be located as close as possible to the IC, and wiring should be as short as
possible.
If hFE value of the PNP transistor is too high, output voltage may rise at low load current (less than 1mA).
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