AP5725
WHITE LED STEP-UP CONVERTER
Description |
Pin Assignments |
The AP5725 is a step-up DC/DC converter specifically designed to drive white LEDs with a constant current. The device can drive 2 ~ 6 LEDs in series from a Li-Ion cell. Series connection of the LEDs provides identical LED currents resulting in uniform brightness and eliminates the need for ballast resistors. For driving higher number of LEDs, AP5725 also supports a single feedback of parallel connected multiple strings of equal number of LEDs.
The AP5725 switches at 1.2MHz that allows the use of tiny external components. A low 0.25V feedback voltage minimizes power loss in the current setting resistor for better efficiency.
(Top View)
SW |
1 |
6 |
VIN |
(Top View) |
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GND |
2 |
5 |
SW |
1 |
6 |
GND |
OVP |
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VIN |
2 |
5 |
FB |
FB |
3 |
74 |
EN OVP |
3 |
4 |
EN |
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SOT26 / TSOT23-6 |
DFN2020C-6 |
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Features |
Applications |
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• High efficiency: 84% typical |
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Cellular Phones |
• Fast 1.2MHz switching frequency |
• PDAs, Hand held Computers |
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• Current limit and UVLO protections |
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Digital Cameras |
• Internal thermal shutdown |
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MP3 Players |
• Internal Over Voltage Protection |
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GPS Receivers |
•Integrated soft-start function
•SOT26, TSOT23-6 and DFN2020C-6: Available in “Green” Molding Compound (No Br, Sb)
•Lead Free Finish/ RoHS Compliant (Note 1)
Notes: 1. EU Directive 2002/95/EC (RoHS). All applicable RoHS exemptions applied. Please visit our website at http://www.diodes.com/products/lead_free.html.
Typical Application Circuit
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L1 |
D1 |
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22uH |
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VIN |
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COUT |
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CIN |
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1uF |
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1uF |
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VIN |
SW |
2~6 LEDs |
ON OFF |
AP5725OVP |
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EN |
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PWM Dimming |
FB |
RSET |
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GND |
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12 |
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Figure 1. Typical Application Circuit
AP5725 |
1 of 17 |
July 2010 |
Document number: DS31844 Rev. 3 - 2 |
www.diodes.com |
© Diodes Incorporated |
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AP5725 |
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WHITE LED STEP-UP CONVERTER |
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Pin Descriptions |
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Pin Name |
Description |
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SW |
Switch Pin. Connect inductor/diode here. Minimize trace area at this pin to reduce EMI. |
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GND |
GND pin. |
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FB |
Feedback Pin. Reference voltage is 0.25V. Connect cathode of lowest LED and a sense |
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resister here. Calculate resistor value according to the formula: RSET = 0.25V / ILED |
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Converter On/Off Control Input. A high input at EN turns the converter On, and a low input |
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EN |
turns it off. If On/Off control is not needed, connect EN to the input source for automatic |
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startup. The EN pin cannot be left floating. |
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OVP |
Output Voltage detect pin for over voltage protection. |
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VIN |
Input Supply Pin. Must be locally bypassed with 1μF or 2.2μF to reduce input noise. |
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Functional Block Diagram
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Rc |
- |
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A1 |
+ |
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Cc |
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FB 3 |
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VIN 6 |
VREF |
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0.25V |
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EN 4 
Enable
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OVP |
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5 |
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Comparator |
1 SW |
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Driver |
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A2 |
Q1 |
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+ |
CONTROL |
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LOGIC |
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OTP |
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Σ |
+ |
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- |
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RAMP |
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Generator |
2 GND |
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1.2MHz |
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Oscillator |
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AP5725 |
2 of 17 |
July 2010 |
Document number: DS31844 Rev. 3 - 2 |
www.diodes.com |
© Diodes Incorporated |
AP5725
WHITE LED STEP-UP CONVERTER
Absolute Maximum Ratings
Symbol |
Parameter |
Rating |
Unit |
VIN |
VIN Pin Voltage |
-0.3~7 |
V |
VSW |
SW Voltage |
-0.3~34 |
V |
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VOVP |
OVP Pin Voltage |
-0.3~35 |
V |
VFB |
Feedback Pin Voltage |
-0.3~7 |
V |
EN |
EN |
-0.3~7 |
V |
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TJ(MAX) |
Maximum Junction Temperature |
150 |
oC |
TLEAD |
Lead Temperature |
300 |
oC |
TST |
Storage Temperature Range |
-65 to +150 |
oC |
Caution: Operation above the absolute maximum ratings can cause device failure. These values, therefore, must not be exceeded under any condition. Operation at the absolute maximum rating for extended periods, may reduce device reliability.
Recommended Operating Conditions
Symbol |
Parameter |
Min |
Max |
Unit |
VIN |
Input Voltage |
2.7 |
5.5 |
V |
TJ |
Operating Junction Temperature |
-40 |
125 |
oC |
TA |
Operating Ambient Temperature |
-40 |
85 |
oC |
AP5725 |
3 of 17 |
July 2010 |
Document number: DS31844 Rev. 3 - 2 |
www.diodes.com |
© Diodes Incorporated |
AP5725
WHITE LED STEP-UP CONVERTER
Electrical Characteristics (VIN = 3.6V, TA = 25°C, unless otherwise specified.)
Symbol |
Parameter |
Conditions |
Min |
Typ. |
Max |
Unit |
System Supply Input |
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VIN |
Operating Input Voltage |
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2.7 |
- |
5.5 |
V |
UVLO |
Under Voltage Lockout |
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2.2 |
2.4 |
V |
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Under Voltage Lockout Hysteretic |
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85 |
- |
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IQ |
Quiescent Current |
FB=0.35V, No Switching |
- |
500 |
- |
μA |
ISD |
Shutdown Current |
VEN < 0.4V |
- |
0.1 |
1 |
μA |
Oscillator |
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FOSC |
Operation Frequency |
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1 |
1.2 |
1.4 |
MHz |
Dmax |
Maximum Duty Cycle |
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90 |
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% |
Reference |
Voltage |
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VFB |
Feedback Voltage |
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0.225 |
0.25 |
0.275 |
V |
IFB |
FB Pin Bias Current |
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10 |
45 |
100 |
nA |
MOSFET |
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Rds(on) |
On Resistance of MOSFET |
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0.95 |
1.2 |
Ω |
IOCP |
Switching Current Limit |
Normal Operation |
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750 |
- |
mA |
Control and |
Protection |
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EN |
Voltage High |
ON |
1.5 |
- |
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V |
EN |
Voltage Low |
OFF |
- |
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0.4 |
V |
IEN |
EN Pin Pull Low Current |
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4 |
6 |
μA |
OVP |
OVP Threshold |
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26 |
30 |
34 |
V |
θJA |
Thermal Resistance Junction-to- |
SOT26 (Note 2) |
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162 |
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oC/W |
TSOT23-6 (Note 2) |
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152 |
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Ambient |
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DFN2020C-6 (Note2) |
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200 |
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θJC |
Thermal Resistance Junction-to- |
SOT26 (Note 2) |
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36 |
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oC/W |
TSOT23-6 (Note 2) |
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32 |
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Case |
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DFN2020C-6 (Note 2) |
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30 |
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Notes: 2. Test condition for SOT26, TSOT23-6 and DFN2020C-6: Device mounted on FR-4 substrate, single-layer PC board, 2oz copper, with minimum recommended pad layout
AP5725 |
4 of 17 |
July 2010 |
Document number: DS31844 Rev. 3 - 2 |
www.diodes.com |
© Diodes Incorporated |
AP5725
WHITE LED STEP-UP CONVERTER
Typical Performance Characteristics (6 LEDs ; VIN = 3.6V ; IOUT = 25mA)
VIN vs. Shutdown Current
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1 |
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700 |
Shutdown Current(uA) |
0.8 |
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Quiescent Current(uA) |
600 |
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500 |
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0.6 |
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400 |
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0.4 |
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300 |
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0.2 |
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200 |
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100 |
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0 |
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0 |
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2.5 |
3 |
3.5 |
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4.5 |
5 |
5.5 |
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VIN (V)
VIN vs. Quiescent Current
2.5 |
3 |
3.5 |
VIN4(V) |
4.5 |
5 |
5.5 |
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VIN vs. Frequency |
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1.25 |
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Frequency(MHz) |
1.2 |
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1.15 |
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1.1 |
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1.05 |
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1 |
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2.5 |
3 |
3.5 |
4 |
4.5 |
5 |
5.5 |
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VIN (V) |
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VIN vs. Max Duty |
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100 |
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Max Duty(%) |
95 |
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90 |
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85 |
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80 |
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2.5 |
3 |
3.5 |
4 |
4.5 |
5 |
5.5 |
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VIN(V) |
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VIN vs. Feedback Voltage |
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0.3 |
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0.3 |
Voltage(V) |
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Voltage(V) |
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0.28 |
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0.28 |
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0.26 |
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0.26 |
Feedback |
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Feedback |
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0.24 |
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0.24 |
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0.22 |
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0.22 |
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0.2 |
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0.2 |
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2.5 |
3 |
3.5 |
4 |
4.5 |
5 |
5.5 |
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0 |
VIN (V)
IOUT vs. Feedback Voltage
10 |
20 |
30 |
40 |
50 |
IOUT (mA)
AP5725 |
5 of 17 |
July 2010 |
Document number: DS31844 Rev. 3 - 2 |
www.diodes.com |
© Diodes Incorporated |
AP5725
WHITE LED STEP-UP CONVERTER
Typical Performance Characteristics (Continued)
OVP Threshold(V)
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VIN vs. OVP Threshold |
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Temperature vs. Shutdown Current |
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35 |
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Current(uA) |
1 |
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33 |
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0.8 |
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31 |
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Shutdown |
0.6 |
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29 |
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0.4 |
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27 |
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0.2 |
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25 |
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0 |
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2.5 |
3 |
3.5 |
4 |
4.5 |
5 |
5.5 |
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-50 |
-25 |
0 |
25 |
50 |
75 |
100 |
125 |
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VIN (V) |
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Temperature ( ) |
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Temperature vs. OVP Threshold
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Threshold(V) |
30 |
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OVP |
20 |
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-50 |
-25 |
0 |
25 |
50 |
75 |
100 |
125 |
Temperature ( )
Temperature vs. Feedback Voltage
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0.28 |
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Voltage(V) |
0.27 |
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VIN = 4.2V |
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0.26 |
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Feedback |
0.25 |
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VIN = 3.6V |
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0.24 |
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0.23 |
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-50 |
-25 |
0 |
25 |
50 |
75 |
100 |
125 |
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Temperature( ) |
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Temperature vs. Frequency
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1.7 |
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VIN = 4.2V |
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(MHZ) |
1.4 |
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1.1 |
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VIN = 3.6V |
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Frequency |
0.8 |
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0.5 |
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0.2 |
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-50 |
-25 |
0 |
25 |
50 |
75 |
100 |
125 |
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Temperature ( ) |
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AP5725 |
6 of 17 |
July 2010 |
Document number: DS31844 Rev. 3 - 2 |
www.diodes.com |
© Diodes Incorporated |
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