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PDF APW7236 Data sheet ( Hoja de datos )
| Número de pieza | APW7236 | |
| Descripción | Step-Up Converter | |
| Fabricantes | ANPEC | |
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APW7236
1.5MHz Step-Up Converter for White LEDs
Features
General Description
• Wide Input Voltage from 2.7V to 6V
• Fixed 1.5MHz Switching Frequency
• Reference Voltage : 0.2V
• PWM Brightness Control with Wide Frequency
Range of 100Hz to 100kHz
• Build-In Power MOSFET : 0.2Ω
• Open-LED Protection
• Under-Voltage Lockout Protection
• Over-Temperature Protection
• <1µA Quiescent Current during Shutdown
• TSOT-23-6A and TDFN2x2-8 Package
• Halogen and Lead Free Available
(RoHS Compliant)
Applications
The APW7236 is a current-mode and fixed frequency
boost converter with an integrated N-FET to drive white
LEDs.
The series connection allows the LED current to be iden-
tical for uniform brightness. Its low on-resistance of NFET
and low feedback voltage reduce power loss and achieve
high efficiency. Fast switching frequency(1.5MHz typical)
allows using small-size inductor and both of input and
output capacitors. An over voltage protection function,
which monitors the output voltage via OVP pin, stops
switching of the IC if the OVP voltage exceeds the over
voltage threshold. An internal soft-start circuit eliminates
the inrush current during start-up.
The APW7236 also integrates under-voltage lockout, over-
temperature protection, and current limit circuits to pro-
tect the IC in abnormal conditions. The APW7236 is avail-
able in a TSOT-23-6A and TDFN2x2-8 package.
• White LED Display Backlighting
• Cell Phone and Smart Phone
• PDA, PMP, MP3
• Digital Camera
Simplified Application Circuit
Pin Configuration
TSOT-23-6A
Top View
LX 1
GND 2
FB 3
6 VIN
5 OVP
4 EN
VIN
C1
4.7µF
OFF ON
L1
4.7µH
VIN LX
GND
OVP
EN FB
ILED
VOUT
C2
µF
7~9 strings
R1
TDFN2x2-8
(Top View)
GND 1
VIN 2
OVP 3
EN 4
GND
8 LX
7 NC
6 FB
5 GND
ANPEC reserves the right to make changes to improve reliability or manufacturability without notice, and
advise customers to obtain the latest version of relevant information to verify before placing orders.
Copyright © ANPEC Electronics Corp.
Rev. A.4 - Sep., 2012
1
www.anpec.com.tw
1 page  
APW7236
Typical Operating Characteristics
(Refer to the application circuit in the section "Typical Application Circuits", VIN=3.6V, TA=25oC, 6WLEDs unless
otherwise specified )
Supply Voltage vs. Efficiency
100
EN Dimming Duty Cycle vs.
WLED Current
250
80
60
L=4.7uH
L=10uH
40
20
0
2.7 3 3.3 3.6 3.9 4.2 4.5 4.8 5.1
Supply Voltage (V)
Supply Voltage vs. WLED Current
210
205
200
195
190
2.7 3.2 3.7 4.2 4.7 5.2
Supply Voltage (V)
Supply Voltage vs. Switch ON Resistance
0.5
200
150
100kHz
100
50kHz
50
20kHz
0
0
100
10 20 30 40 50 60 70 80 90 100
EN Dimming Duty Cycle (%)
Supply Voltage vs. Maximum
Duty Cycle
90
80
70
60
50
40
2 2.5 3 3.5 4 4.5 5 5.5 6
Supply Voltage (V)
0.4
0.3
0.2
0.1
0
2 2.5 3 3.5 4 4.5 5 5.5 6
Supply Voltage (V)
Copyright © ANPEC Electronics Corp.
Rev. A.4 - Sep., 2012
5
www.anpec.com.tw
5 Page 
APW7236
Application Information (Cont.)
Output Capacitor Selection (Cont.)
For ceramic capacitor application, the output voltage ripple
is dominated by the ∆VCOUT. When choosing the input and
output ceramic capacitors, the X5R or X7R with their
good temperature and voltage characteristics are
recommended.
Setting the LED Current
In figure 1, the converter regulates the voltage on FB pin,
connected with the cathod of the lowest LED and the cur-
rent-sense resistor R1, at 0.2V (typical). Therefore, the
current (I ), flowing via the LEDs and the R1, is calcu-
LED
lated by the following equation:
ILED
=
0.2V
R1
Layout Considerations
For all switching power supplies, the layout is an impor-
tant step in the design; especially at high peak currents
and switching frequencies. If the layout is not carefully
done, the regulator might show noise problems and duty
cycle jitter.
1. The input capacitor should be placed close to the VIN
and GND. Connecting the capacitor with VIN and GND
pins by short and wide tracks without using any via holes
for good filtering and minimizing the voltage ripple.
2. To minimize copper trace connections that can inject
noise into the system, the inductor should be placed
as close as possible to the LX pin to minimize the noise
coupling into other circuits.
3. The feedback network should be routed away from the
inductor. The feedback pin and feedback network
should be shielded with a ground plane or trace to
minimize noise coupling into this circuit.
4. A star ground connection or ground plane minimizes
ground shifts and noise is recommended.
Copyright © ANPEC Electronics Corp.
Rev. A.4 - Sep., 2012
11
www.anpec.com.tw
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet APW7236.PDF ] | |
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