PSRS-783R3LF Datasheet, PDF (4/4 Pages) PEAK electronics GmbH – 500 mA Switching Regulator

App Notes
The ON/OFF pin provides several features for adjusting and sequencing the power supply, a user has
the flexibility of using the ON/OFF pin as:
1) A digital on/off control by pulling down the ON/OFF pin with an open-drain transistor.
ON/OFF
2) Line UVLO. If desired to achieve a UVLO voltage, an resistor divider from Vin to ON/OFF to GND
can be used to disable the converter until a higher input voltage is achieved. For example, it is not
useful for a converter with 12V output to start up with a 12V input voltage, as the output cannot teach
regulation. To enable the converter when the input voltage reaches 14V, a 51kΩ/5kΩ resistor divider
from Vin to GND can be connected to the ON/OFF pin. Both the precision 1.25V threshold and 150mV
hysteresis are multiplied by the resistor ratio, providing a proportional 12% hysteresis for any startup
threshold. So, the turn off threshold would be between 12.3V to 15.7V.
Vin
DC/DC
+ Vo u t
1 _Converter 5
5 1 KΩ
10 7,9 6
C1
5 KΩ
GND
100µ F
470pF
2) Power supply sequencing. By connecting a small capacitor from ON/OFF to GND, the 2µA current
source and 1.25V threshold can provide a stable and predictable delay between start-up of
multiple power supplies. For example, a start-up delay of roughly 64mS is provided using 100nF,
and roughly 136mS by using 200nF.
Vin
C1
GND
DC/DC
+Vo u t
1 _Converter 5
10 7,9 6
C5
100nF
100µ F
470pF
Delay time: 64mS
Vin
C1
GND
DC/DC
+Vo u t
1 _Converter 5
10 7,9 6
C5
200nF
100µ F
470pF
Delay time: 136mS
Part #
PSRS-783R3LF
PSRS-7805LF
PSRS-7812LF
PSRS-7815LF
Vout
(nominal)
3.3
5
12
15
Vout adjust up R2 (kOhm)
75.10 −10 *Vout
= _{Vout − 3.3}
91.52 − 10 *Vout
=
Vout − 5
287.02 − 20 *Vout
=
Vout − 12
269.37 − 15 *Vout
=
Vout − 15
Vout adjust down R1 (kOhm)
61*Vout − 75.10
= _{3.3 − Vout}
61*Vout − 91.52
=
5 − Vout
71*Vout − 287.02
=
12 − Vout
66 *Vout − 269.37
=
15 − Vout
The R1, R2 which choose from the table 1 equation are used to set the output voltage. Select the R1
or R2 resistor to provide the desired regulation voltage. R1 is used to set the output voltage to lower,
R2 is used to set the output voltage to higher. If no need to adjust the output voltage, please connect a
ceramic capacitor to GND with 470pF typical value. Insure the output voltage is in the adjust range.
PME02-Series – PSRS-78xxLF – Switching Regulator – SMD – Plastic Case
Specification can change without a notice – We accept no liability for any inaccuracy or printing errors.
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