Zxre160 new prod uc t, Application information – Diodes ZXRE160 User Manual
Page 10
ZXRE160
Document number: DS35688 Rev. 2 - 2
10 of 15
June 2012
© Diodes Incorporated
ZXRE160
NEW PROD
UC
T
A Product Line of
Diodes Incorporated
Application Information
(cont.)
⎟
⎠
⎞
⎜
⎝
⎛ +
=
2
R
1
R
1
V
V
REF
OUT
BE
OUT
V
V
2
.
0
V
+
≥
3
R
OUT
IN
I
V
V
3
R
−
=
Figure 8. 1V Current-Boosted Shunt Regulator
Design guide
1. Determine
I
OUT
and choose a suitable transistor taking power dissipation into consideration.
2. Determine
I
B
from
)
1
h
(
I
I
(min)
FE
(max)
OUT
B
+
=
3. Determine
I
R3
from
(max)
OUT
3
R
I
I
=
4.
Determine R3 from
3
R
OUT
IN
I
V
V
3
R
−
=
5.
It is best to let the ZXRE160 supply as much current as it can before bringing Q1 into conduction. Not only does this minimize the strain on
Q1, it also guarantees the most stable operation. Choose a nominal value between 10mA and <15mA for this current, I
R4
.
Calculate R4 from
4
R
BE
I
V
4
R
=
V
OUT
goes low and LED is lit when monitored supply
⎟
⎠
⎞
⎜
⎝
⎛ +
>
2
R
1
R
1
REF
V
M
V
3
R
I
)
2
.
0
F
V
(
IN
V
3
R
+
−
=
)
MAX
(
F
I
3
R
I
mA
15
≤
≥
V
F
and I
F
are forward voltage drop and current of LED1.
Figure 9. 1.15V Over-Voltage Indicator