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PDF AP2961A Data sheet ( Hoja de datos )
| Número de pieza | AP2961A | |
| Descripción | 42V 3A CC/CV Step-Down DC/DC Converter | |
| Fabricantes | Chipown | |
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AP2961A
Chipown
TEL:15622809726
42V 3A CC/CV Step-Down DC/DC Converter
General Description
AP2961A is a wide input voltage, high efficiency
CC/CV step-down DC/DC converter that operates in
either CV (Constant Output Voltage) mode or CC
(Constant Output Current) mode. AP2961A provides
up to 3A output current at 125kHz switching frequency.
AP2961A eliminates the expensive, high accuracy
current sense resistor, making it ideal for battery
charging applications and adaptors with accurate
current limit. The AP2961A achieves higher efficiency
than traditional constant current switching regulators
by eliminating its associated power loss on the
additional current sensing resistor. AP2961A provides
OVP pin for output over voltage protection.
AP2961A integrates adaptive gate drive to achieve
excellent EMI performance passing EN55022 Class B
EMC standard without adding additional EMI
components while maintaining high conversion
efficiency.
Protection features include cycle-by-cycle current limit,
thermal shutdown, and frequency foldback at short
circuit. AP2961A are available in a SOP8-PP package
and require very few external devices for operation.
Applications
Car Charger/ Adaptor
Rechargeable Portable Devices
General-Purpose CC/CV Supply
Features
42V Input Voltage Surge
40V Steady State Operation
Up to 3A Output Current
Output Voltage up to 12V
125kHz Switching Frequency
Up to 91% Efficiency
Stable with Low-ESR Ceramic Capacitors to Allow Low-
Profile Designs
Integrated Over Voltage Protection
Excellent EMI Performance
Constant Current Control Without Additional Current
Sensing Resistor Improves Efficiency and Lowers Cost.
Resistor Programmable Current Limit from 1.5A to 3.5A
Up to 0.5V Excellent Cable Voltage Drop Compensation
±7.5% CC Accuracy
2% Feedback Voltage Accuracy
Advanced Feature Set
Integrated Soft Start
Thermal Shutdown
Cycle-by-Cycle Current Limit
SOP8-PP Package
Package
SOP8-PP
BS 1
8 ISET
VIN 2
7 OVP
EP
SW 3
6 COMP
GND 4
5 FB
Typical Application Circuit
R4 22Ω
VIN
C1
100uF
1
C3
22nF
2
VIN
BS
3
SW
C2
4.7uF
AP2961A
8
ISET
5
FB
R5
10K
GND
COMP OVP 7
4,9 6
C5
220p
C4
4.7nF
R3
4.7K
L1 47uH
D1 R1
SK54 270K
R2
51K
C6
1nF
R6
75K
R7
12K
VOUT
5V/2.4A
C7
4.7uF
C8
470uF
Figure 1. Typical Application Circuit with AP2961A
100
90
80
70
60
50
40
0
η vs Io
VIN=12V
VIN=24V
500
1000
1500
2000
2500
Io(mA)
Figure 2. Typical Efficiency Curve
13/F, Building C, Wangzhuang Technology Innovation Center, Longshan Road,New District, Wuxi Tel: +86(510)85217718 http://www.chipown.com.cn V0.0 1 / 9
1 page  
AP2961A
Chipown
Figure 5:
Curve for Programming Output CC Current
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
8
Output Current vs RISET
VIN=24V,Vout=4V
10 12 14 16 18 20 22 24
Riset(KΩ)
Inductor Selection
The inductor maintains a continuous current to the
output load. This inductor current has a ripple that is
dependent on the inductance value:
Higher inductance reduces the peak-to-peak ripple
current. The trade off for high inductance value is the
increase in inductor core size and series resistance, and
the reduction in current handling capability. In general,
select an inductance value L based on ripple current
requirement:
( )L = VOUT × VIN − VOUT
V f I KIN SW LOADMAX RIPPLE
where VIN is the input voltage, VOUT is the output
voltage, fSW is the switching frequency, ILOADMAX is the
maximum load current, and KRIPPLE is the ripple factor.
Typically, choose KRIPPLE = 30% to correspond to the
peak-to-peak ripple current being 30% of the maximum
load current.
With a selected inductor value the peak-to-peak
inductor current is estimated as:
( )ILPK −PK
= VOUT × VIN - VOUT
L ×VIN × fSW
The peak inductor current is estimated as:
I LPK
= I LOADMAX
+
1
2
I LPK
− PK
The selected inductor should not saturate at ILPK. The
maximum output current is calculated as:
I OUTMAX
= I LIM
−
1
2
I LPK
− PK
LLIM is the internal current limit, which is typically
4.5A, as shown in Electrical Characteristics Table.
External High Voltage Bias Diode
It is recommended that an external High Voltage Bias
diode be added when the system has a 5V fixed input
or the power supply generates a 5V output. This helps
improve the efficiency of the regulator. The High
Voltage Bias diode can be a low cost one such as
IN4148 or BAT54.
Figure 6:
External High Voltage Bias Diode
5V
BS
22nF
SW
This diode is also recommended for high duty cycle
operation and high output voltage applications.
Input Capacitor
The input capacitor needs to be carefully selected to
maintain sufficiently low ripple at the supply input of
the converter. A low ESR capacitor is highly
recommended. Since large current flows in and out of
this capacitor during switching, its ESR also affects
efficiency.
The input capacitance needs to be higher than 10μF.
The best choice is the ceramic type, however, low ESR
tantalum or electrolytic types may also be used
provided that the RMS ripple current rating is higher
than 50% of the output current. The input capacitor
should be placed close to the IN and GND pins of the
IC, with the shortest traces possible. In the case of
tantalum or electrolytic types, they can be further away
if a small parallel 10μF ceramic capacitor is placed
right next to the IC.
Output Capacitor
The output capacitor also needs to have low ESR to
keep low output voltage ripple. The output ripple
voltage is:
VRIPPLE
=
I K ROUTMAX RIPPLE ESR
+
28 ×
VIN
fSW 2LCOUT
Where IOUTMAX is the maximum output current, KRIPPLE
is the ripple factor, RESR is the ESR of the output
capacitor, fSW is the switching frequency, L is the
inductor value, and COUT is the output capacitance. In
the case of ceramic output capacitors, RESR is very
small and does not contribute to the ripple. Therefore, a
lower capacitance value can be used for ceramic type.
In the case of tantalum or electrolytic capacitors, the
ripple is dominated by RESR multiplied by the ripple
current. In that case, the output capacitor is chosen to
have sufficiently low ESR.
For ceramic output capacitor, typically choose a
13/F, Building C, Wangzhuang Technology Innovation Center, Longshan Road,New District, Wuxi Tel: +86(510)85217718 http://www.chipown.com.cn V0.0 5 / 9
5 Page | ||
| Páginas | Total 9 Páginas | |
| PDF Descargar | [ Datasheet AP2961A.PDF ] | |
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