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PDF LD7270 Data sheet ( Hoja de datos )
| Número de pieza | LD7270 | |
| Descripción | Smart Photoflash Capacitor Charger | |
| Fabricantes | Leadtrend | |
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LD7270
6/18/2010
Smart Photoflash Capacitor Charger with Integrated MOS
REV：03
General Description
The LD7270 is an ideal charge control IC for flash units,
featuring internal soft start, adjustable charging current
and output voltage. It provides a charging algorithm to
speed up the charging with higher efficiency. The LD7270
can operate in desired constant peak current mode
through adjusting RI between ISET pin and GND. As well,
LD7270 uses separate source and sink pin of IGBT driver,
which enables the users to easily meet different IGBT
application requirements.
The LD7270 is available in a space-saving WDFN-10L
3x3 package and is ideal for DSC flash unit.
g Patented
Features
• 1.8V~6V Battery Voltage Range
• Adjustable Output Voltage
• Adjustable Input Current
• Integrated 47V Power MOS
• Separate Source and Sink Pin of IGBT Driver
• False Triggering Prevention
• Soft Start
• Output Voltage Overcharge Protection
• High Efficiency
Applications
• DSC Flash Unit
• Cell Phone with Camera
Typical Application
RI
=
40000
IPK -PRI
(Ω)
Fig.1
Leadtrend Technology Corporation
LD7270-DS-03, June 2010
1
www.leadtrend.com.tw
1 page  
Block Diagram
LD7270
Absolute Maximum Ratings
VCC and VBAT Pin
-0.3V~6.5V
FB pin
-0.45V~6.5V
Charge, Trigger, DONE#, ISET, OUTP and OUTN pin
LX pin<200ns
-0.3V~6.5V
-0.3V~47V
DC -0.3V~42V
LX Current
Package Thermal Resistance WDFN-10L 3mm×3mm, θJA
Operating Temperature Range
Storage Temperature Range
Junction Temperature
Lead Temperature (Soldering, 10sec)
3.3A
60°C/W
-30°C to 85°C
-55°C to 125°C
125°C
260 °C
ESD Level (Human Body Model)
2KV
ESD Level (Machine Model)
200V
Caution:
Stresses beyond the ratings specified in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only
rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification
is not implied.
Leadtrend Technology Corporation
LD7270-DS-03, June 2010
5
www.leadtrend.com.tw
5 Page 
LD7270
Fig. 19
The signal of IGBT gate will be high according to following
sequence.
1. VCC>UVLO (ON) (typical 2.65V)
2. Charge pin is high (the pulse width should be larger
than 100μs)
3. Trigger pin is high and charge pin is low.
D1/CHBD 4004
C2
120μF
R1
130kΩ/1%
R2
130kΩ/1%
Maximum ON Time
To protect against insufficient current from a poor power
source (ie., an almost discharged battery) and
unreachable current limit value, the LD7270 employs
maximum on-time function for it. As soon as ON time of
charging period exceeds 30μs, the LD7270 will be latched
off in regardless of current limit detection.
Adjust Output Voltage
A resistor divider can be connected to the center of the
dual diode to eliminate the leakage current after the
charging completes. Fig.20 shows the application circuit
of resistor divider.
VDD
100kΩ
FB
R3
1kΩ/1%
DONE#
Fig. 20
VOUT
= 1.15 × ⎜⎛1+
⎝
R1+ R2
R3
⎟⎞
⎠
It’s not recommended to choose the resistor larger than
1KΩ to connect with FB to GND (R3 in Fig. 20), since a
larger resistor 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.
Output Voltage Overcharge Protection
As shown in Fig. 1, Fig. 2, Fig. 3 or Fig. 4, the FB pin may
Leadtrend Technology Corporation
LD7270-DS-03, June 2010
11
www.leadtrend.com.tw
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LD7270.PDF ] | |
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