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MAX1720EUTG

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18
MAX1720
http://onsemi.com
10
+
+
6
4
2
3
1
OSC
Capacitors = 10 mF
+
V
in
5
V
out
+
+
Figure 28. Positive Output Voltage Tripler
A single device can be used to construct a positive voltage tripler. The output voltage is approximately equal to 3V
in
minus
the forward voltage drop of each external diode. The performance characteristics for the above converter are shown below.
Note that curves A and C show the circuit performance with economical 1N4148 diodes, while curves B and D are with lower
loss MBRA120E Schottky diodes.
6.0
2.0
4.0
0
8.0
10.0
12.0
14.0
I
out
, OUTPUT CURRENT (mA)
V
out
, OUTPUT VOLTAGE (V)
0302010 40
F
igure 29. Tripler Load Regulation, Output Voltage vs. Output Current
A
B
T
A
= 25°C
C
D
A 3.0 1N4148
B 3.0 MBRA120E
Curve V
in
(V) All Diodes
111
97
R
out
(W)
C 5.0 1N4148
D 5.0 MBRA120E
85
75
+
6
4
2
3
1
OSC
+
V
in
5
−V
out
+
Figure 30. Load Regulated Negative Output Voltage
Capacitors = 10 mF
100 k
MAX1720
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11
A zener diode can be used with the shutdown input to provide closed loop regulation performance. This significantly reduces
the converter’s output resistance and dramatically enhances the load regulation. For closed loop operation, the desired
regulated output voltage must be lower in magnitude than −V
in
. The output will regulate at a level of −V
Z
+ V
th(SHDN)
. Note that
the shutdown input voltage threshold is typically 0.5 V
in
and therefore, the regulated output voltage will change proportional
to the converter’s input. This characteristic will not present a problem when used in applications with constant input voltage.
In this case the zener breakdown was measured at 25 mA. The performance characteristics for the above converter are shown
below. Note that the dashed curve sections represent the converter’s open loop performance.
0
−2.0
302010
V
out
, OUTPUT VOLTAGE (V)
−5.0
−1.0
I
out
, OUTPUT CURRENT (mA)
−4.0
−3.0
40 6050
Figure 31. Load Regulation, Output Voltage vs.
Output Current
A
B
T
A
= 25°C
A 3.3 V 4.5
B 5.0 V 6.5
Curve V
in
(V) V
z
(V)
−2.8
−3.8
V
out
(V)
Capacitors = 10 mF
+
6
4
2
3
1
OSC
+
V
in
5
−V
out
+
R
1
R
2
10 k
Figure 32. Line and Load Regulated Negative Output Voltage
MAX1720
http://onsemi.com
12
An adjustable shunt regulator can be used with the shutdown input to give excellent closed loop regulation performance. The
shunt regulator acts as a comparator with a precise input offset voltage which significantly reduces the converter’s output
resistance and dramatically enhances the line and load regulation. For closed loop operation, the desired regulated output
voltage must be lower in magnitude than −V
in
. The output will regulate at a level of −V
ref
(R
2
/R
1
+ 1). The adjustable shunt
regulator can be from either the TLV431 or TL431 families. The comparator offset or reference voltage is 1.25 V or 2.5 V
respectively. The performance characteristics for the converter are shown below. Note that the dashed curve sections represent
the converter’s open loop performance.
−2.0
−3.0
−1.0
−4.0
−5.0
I
out
, OUTPUT CURRENT (mA)
V
out
, OUTPUT VOLTAGE (V)
030 7010 20 40 50 60
Figure 33. Load Regulation, Output Voltage vs.
Output Current
A
B
T
A
= 25°C
A 3.0 5.0 k
B 5.0 20 k
Curve V
in
(V)
R
2
(W)
−1.8
−3.6
V
out
(V)
10 k
10 k
R
1
(W)
−2.0
−3.0
−1.0
−4.0
1.0 3.02.0 4.0 5.0 6
.0
0
V
in
, INPUT VOLTAGE (V)
V
out
, OUTPUT VOLTAGE (V)
Figure 34. Line Regulation, Output Voltage vs.
Input Current
I
out
= 25 mA
R
1
= 10 k
R
2
= 20 k
T
A
= 25°C
+
6
4
2
3
1
OSC
Capacitors = 10 mF
V
in
5
6
4
2
3
1
OSC
+
5
−V
out
+
+
Figure 35. Paralleling Devices for Increased Negative Output Current
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18

MAX1720EUTG

Mfr. #:
Buy MAX1720EUTG
Manufacturer:
ON Semiconductor
Description:
Switching Voltage Regulators Switched Cap Voltage Inverter w/Shutdown
Lifecycle:
New from this manufacturer.
Delivery:
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