R1511 Datasheet, PDF (9/20 Pages) RICOH electronics devices division – Input Voltage Range 3.5V to 36V

TYPICAL APPLICATIONS
VDD
VOUT
CIN ^R1511xxxxB
Series
GND
CE
COUT
CIN=Ceramic 1.0μF
COUT=Ceramic 6.8μF
R1511x
VDD
VOUT
CIN ^R1511x001C
Series
COUT
R2
GND
RFB ^VFB
R3
CIN=Ceramic 1.0μF
COUT=Ceramic 6.8μF
NOTES CONCERNING EXTERNAL PARTS
Phase Compensation
In the R1511x Series, phase compensation is provided to secure stable operation even when the load current
is varied. For this purpose, please make sure to use a COUT capacitor.
In case of using a tantalum type capacitor and the ESR (Equivalent Series Resistance) value of the capacitor
is large, the output might be unstable. Evaluate the circuit including consideration of frequency characteristics.
Depending on the capacitor size, manufacturer, and part number, the bias characteristics and temperature
characteristics are different. Evaluate the circuit taking actual characteristics into account.
PCB Layout and GND Wiring
Ensure the VDD and GND lines are sufficiently robust. If their impedance is too high, noise pickup or unstable
operation may result. Connect a CIN capacitor with 1.0µF or more value between the VDD and GND pins, and as
close as possible to the pins. Likewise, connect a COUT capacitor with suitable values between the VOUT and GND
pins, and as close as possible to the pins (Please refer to the Typical Application above).
In the case of using HSOP-6J package, please make sure to wire No. 2, No. 3, and No. 5 pins to the GND
plane. Also, in the case of using TO-252-5-P2 package, please make sure to wire No. 2 and No. 3 pins to the
GND plane.
Thermal Shutdown
R1511x contains a thermal shutdown circuit, which stops regulator operation if the junction temperature of
R1511x becomes higher than 160ºC (Typ.). Additionally, if the junction temperature after the regulator being
stopped decreases to a level below 135ºC (Typ.), it restarts regulator operation. As a result the operation of the
thermal shutdown circuit causes the regulator repeatedly to turn off and on until the causes of overheating are
removed. As a consequence a pulse shaped output voltage occurs.
Output Voltage Setting Method (R1511x001C)
R1511x001C can be adjusted the output voltage up to 12.0V by using the external divider resistors. The output
voltage can be calculated by the following equation.
VOUT=VFB×(R2+R3)/R3
However, output voltage will be as large as “R2×IFB” by the current flowing through the resistor in the IC.
Because IFB = VFB/RFB, “R2×IFB” cause of error is as follows.
R2×IFB=R2×VFB/RFB=VFB×R2/RFB
For better accuracy, choosing R2<<RFB reduces this error. RFB of R1511x is approximately min 1.0MΩ
(guaranteed by design).
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