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PDF LD7265A Data sheet ( Hoja de datos )
| Número de pieza | LD7265A | |
| Descripción | Smart Photoflash Capacitor Charger | |
| Fabricantes | Leadtrend | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LD7265A (archivo pdf) en la parte inferior de esta página. Total 21 Páginas | ||
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LD7265A
6/25/2008
Smart Photoflash Capacitor Charger with Integrated MOS
REV:01
General Description
The LD7265A is an ideal charge control IC for flash units
with internal soft start, adjustable charging current and
output voltage. It provides a proprietary charging algorithm
to speed up the charging with more efficiency. The LD7265A
operates in the constant peak current mode, while the peak
current limit can be adjusted to eight different levels
between 0.54A to 1.8A, by clocking the CHARGE Pin. As
well, LD7265A separates the source and sink pin of IGBT
driver, which enables the users to easily meet the
requirement of any different IGBT application.
The LD7265A is available in a space-saving DFN10
package and is ideal for DSC flash unit.
Features
• Adjustable Output Voltage
• 1.8V~6V Battery Voltage Range
• Tiny Transformer
• Integrated 45V Power Switch
• Programmable eight-level Current Limit
• Separate Source and Sink Pin of IGBT Driver
• Output Voltage Overcharge Protection
• Lower Charging Current Drop Compensation
Applications
• DSC Flash Unit
• Cell Phone with Camera
g Patented
Typical Application
D 1/FT 01P80
C2
1 2 0μ F
R1
130K
VDD
R1
1 0 0K
DO NE #
R2
1 30 K
R3
1K
IG BT Gate
RP
RN
T1*
VB AT
C1
2 2μ F
VCC
1μF
VCC
FB
LX
Cs/ 22 0 PF*
V BAT
LD7265A
DONE #
CHARG E
Charge
OUTP
OUTN
TR IGGER
GND
Tr ig ge r
* If LX pin spike is over 45V, please add Cs to reduce spike.
Cs< 220pF is recommended.
Fig.1
Leadtrend Technology Corporation
LD7265A-DS-01 June 2008
1
www.leadtrend.com.tw
1 page  
Electrical Characteristics
(TA = +25oC unless otherwise stated, VCC=3.3V)
PARAMETER
CONDITIONS
Input Power
Operating Voltage VCC
Shutdown Current ICC
Nominal Supply Current
FB
Reference Voltage
Reference Voltage Tolerance
Sample time of FB detection
Charge=Off, Trigger=Off
VCC=3.3V, D=50%
LX pin
Primary Side Current Limit- ILIM1
Primary Side Current Limit- ILIM2
Primary Side Current Limit- ILIM3
Primary Side Current Limit- ILIM4
Primary Side Current Limit- ILIM5
Primary Side Current Limit- ILIM6
Primary Side Current Limit- ILIM7
Primary Side Current Limit- IIM8
On resistance
LX leakage current
IGBT Driver
OUTP Resistance
OUTN Resistance
Rising Time
Falling Time
ON/OFF
Trigger On/Off
Charge On/Off
ILIM Clock High time at Charge Pin
ILIM Clock Low time at Charge Pin
Note
Vcc=5V, ILX=0.54A
VLX=40V
VCC=3.3V
VCC=3.3V
VCC=3.3V, CL=3.9nF
VCC=3.3V, CL=3.9nF
Enabled
Disabled
Enabled
Disabled
Initial Pulse
Subsequent Pulses
Leadtrend Technology Corporation
LD7265A-DS-01 June 2008
5
www.leadtrend.com.tw
LD7265A
MIN
TYP
MAX UNITS
2.8 5.5 V
1.5 μA
1 mA
1.15 V
-1.5
+1.5
%
270 300 330 nS
0.486
0.54
0.595
A
0.72 A
0.90 A
1.08 A
1.26 A
1.44 A
1.62 A
1.62
1.80
1.98 A
270 mΩ
5 μA
6 9Ω
11 17 Ω
90 nS
165 nS
1.4 V
0.6 V
1.4 V
0.6 V
36 μS
5 μS
5 μS
5 Page 
LD7265A
VOUT
= 1.15 × (1 +
R1 + R2 )
R3
It’s not recommended to choose the resistors larger than
1KΩ to connect with FB to GND (R3 in Fig. 21), since
larger resistors would combine with parasitic capacitance
and affect the accuracy of VOUT detection. As well, the
switching nodes such as LX pin or secondary side of XFMR
should be kept routed away from FB pin in such application
of Fig.20 to obtain accurate VOUT detection.
Fig.20 Charging Curren t without Drop Compensa tion
Maximum ON Time
To prevent some worse cases like insufficient current from a
poor power source (ie., an almost discharged battery), and
may never reach current limit value, the LD7265A employs
maximum on-time function for it. Once upon ON time
exceeds 32μS, the LD7265A will latch off regardless of
current limit detection.
Adjust Output Voltage
A resistor divider can be connected to the central of the dual
diode to eliminate the leakage current after the charging
completes. Fig.21 shows the application circuit of resistor
divider.
D1/ CHBD4004
C2
120μF
R1
130K/1%
R2
130K/1%
VDD
R3
1K/1%
FB
100K
RE ADY
Fig.21
Output Voltage Overcharge Protection
As shown in Fig.1, Fig.2, or Fig.3, the FB pin may fail to
reach 1.15V during the charging cycle, either when the R3 is
short to GND or R1 (or R2) open. It will cause VOUT increase
continuously till over the target value of output voltage.
LD7265A features proprietary detecting scheme to
effeteively avoid this phenomenon.
IGBT Driver
LD7265A separates the source and sink pin of IGBT driver,
that enables the users to easily meet the requirement of any
different IGBT applications. Besides, when VCC is under
2.5V (typ), OUTP and OUTN pin will have no output signal
even TRIGGER pin is toggled high.
Rectifying Diode Selection
Choose a rectifying diode with shorter reverse recovery time
to limit the switching loss and increase the charging
efficiency. And in addition, it would allow sufficient peak
reverse voltage and peak forward current rating.
The peak reverse voltage is about:
VPK-R= VOUT+N×VBAT+VSPIKE
The peak forward current is about:
IPK-SEC= Ip / N, IP: peak primary current (A), N: turn ratio
Interface
CHARGE, READY and TRIGGER can be easily interfaced
to a microprocessor.
The CHARGE pin is the ON/OFF control of charging circuit.
Leadtrend Technology Corporation
LD7265A-DS-01 June 2008
11
www.leadtrend.com.tw
11 Page | ||
| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet LD7265A.PDF ] | |
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