sr086 Supertex, Inc., sr086 Datasheet - Page 5

• Manufacturer Part Number: sr086
• Description: Adjustable Off-line Inductorless Switching Regulator
• Manufacturer: Supertex, Inc.

Data Sheet Application Section:
Typical Application Circuit
Output Voltage*
V
feedback resistor R
Leave R
load required for the proper operation of the SR086. Change
R
C
low ESR capacitor with an adequate ripple current rating
(800mA
Since V
mum current available from V
creased due to power considerations.
I
REG(max)
OUT
3
2
R
and R
and C
3
may be adjusted in the range of 9V to 50V*‚ by changing
+ R
= 1.5W / (V
REG
RMS
6
4
3
at 12.4kΩ or less - it assures a minimum 100µA
). Use ceramic for C
is a linear regulator supplied from V
with appropriate voltage ratings. For C
according to the R
4
Equation:
OUT
5
according to the following equation.
- 3.3V), or 60mA, whichever is less.
REG
3
2
+R
.
is reduced as V
4
equation below. Select
OUT
, the maxi-
OUT
3
, use a
where V
is in-
5
X
Input Voltage
To reduce standby power for 230VAC-only applications,
or for supply voltages less than 90Vrms, R
be changed according to the R
should remain at 400kΩ or less. Two resistors in series
are employed to ensure adequate creepage distances for
230VAC operation. For 120VAC-only applications, single re-
sistors may be employed.
Output Ripple*
Storage capacitor C
at 100mA load (I
duced. Conversely, C
Use a low ESR capacitor with an adequate ripple current
rating (800mA
current capability may drop with increased capacitance be-
cause of a smaller conduction angle associated with lower
ripple. Due to feedback hysteresis, ripple cannot be reduced
below 4%.
*V
must not fall below 7.3V.
= V
REG
OUT
requires at least 4V of headroom. Therefore, V
+ 15V
RMS
OUT
Use the minimum anticipated RMS value for V
Take resistor tolerance into account, selecting the
next lower standard value. Choosing a lower value
has no effect other than higher standby power.
for 100mA loads). Effi ciency and output
3
+ I
was sized to provide about 2V
3
REG
may be increased for lower ripple.
). For lighter loads, C
3
+R
4
equation below. R
OUT
3
and R
, including ripple,
SR086
3
may be re-
P-P
4
should
ripple
1
IN
+R
.
2