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PDF LA8509A Data sheet ( Hoja de datos )
| Número de pieza | LA8509A | |
| Descripción | 18V/3A Synchronous Step-Down DC-DC Converter | |
| Fabricantes | INNO-TECH | |
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LA8509A
340KHz, 18V/3A Synchronous Step-Down DC-DC Converter
General Description
Features
The LA8509A is a current mode, synchronous
step-down DC-DC converter that is designed to
meet 3A output current, and utilizes PWM
control scheme that switches with 340KHz
fixed frequency.
The input voltage range of LA8509A is from
4.5V to 18V, and available in adjustable output
voltage from 0.925V to 12V. The supply
current is only 1.3mA during operation and
under 0.3uA in shutdown.
This device provides an enable function that
can be controlled by external logic signal. It
also provides excellent regulation during line
or load transient due to the current mode
operation. Other features of current limit,
soft-start, thermal shutdown protection, and
short circuit protection are also included. Due
to the low RDS(ON) of the internal power
MOSFET, this device provides high efficiency
step-down applications. It is available in
ESOP-8 package.
l Continuous 3A Output Capability
l 0.925V Reference Voltage
l 4.5V to 18V Input Voltage Range
l Adjustable Output from 0.925V to 12V
l 340KHz Oscillation Frequency
l 0.3uA Low Shutdown Current
l 1.3mA Low Supply Current
l Current Mode for Excellent Response
l Support Low ESR Output Ceramic Capacitors
l Internal Current Limit
l Soft-Start
l Short Circuit Protection
l Thermal Shutdown Protection
l ESOP-8 Package
l Meet RoHS Standard
Applications
l Broadband Communication Device
l LCD TV / Monitor
l Storage Device
l Wireless Application
Ordering Information
Marking Information
LA8509A 1 2 3 4
1 (Package Type) => P: ESOP
2 (Number of Pins) => G: 8pin
3 (Output Voltage) => Blank: Adjustable
4 (Special Feature) => Blank: N/A
Available Part Number
LA8509APG
LA8509APG
1234
1 2 (Date Code)
For date code rule, please contact our sales
representative directly
3 4 (Internal Code)
Rev01
-1-
Mar. 07, 2013
www.inno.com.tw
1 page  
LA8509A
Absolute Maximum Ratings
Parameter
Input Voltage
SW Voltage Range
BS Voltage Range
FB / EN / COMP Voltage Range
Storage Temperature Range
Junction Temperature
Lead Soldering Temperature (10 sec)
Rating
20V
-1V ~ VIN+0.3V
VSW–0.3V ~ VSW+6V
-0.3V ~ 6V
-65°C ~ 150°C
150°C
260°C
These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for
prolonged time periods may affect device reliability. All voltages are with respect to ground.
Recommended Operating Conditions
Parameter
Rating
Input Voltage Range
Maximum Junction Temperature
4.5V ~ 18V
125oC
These are conditions under which the device functions but the specifications might not be guaranteed. For
guaranteed specifications and test conditions, please see the Electrical Specifications.
Package Information
Parameter
Thermal Resistance
(Junction to Case)
Thermal Resistance
(Junction to Ambient)
Package
ESOP-8
Symbol
θJC
θJA
Rating
10 oC/W
50 oC/W
Rev01
-5-
Mar. 07, 2013
www.inno.com.tw
5 Page 
LA8509A
Component Selection
Inductor Selection
The conduction mode of power stage depends on input voltage, output voltage, output current,
and the value of the inductor. Select an inductor to maintain this device operating in continuous
conduction mode (CCM). The minimum value of inductor can be determined by the following
procedure.
(1) Calculate the minimum duty ratio:
VOUT + ILOAD × RL + VDS _ B TON
D(MIN) = VIN(MAX) - VDS _ T + VDS _ B = TS
Where RL is the DC resistance of the external inductor, VDS_T is the turn-on voltage of the High-Side
MOSFET, VDS_B is the turn-on voltage of the Low-Side MOSFET, and Ts is the switching period.
This formula can be simplified to
D(MIN ) = V OUT = T ON ; 0 ≤ D ≤ 1
V IN(MAX )
TS
(2) Define a value of minimum current that is approximately 10%~30% of full load current to
maintain continuous conduction mode, usually referred to as the critical current (ICRIT).
IL
ILOAD
ICRIT
T ICRIT = δ × ILOAD ; δ =0.1~0.3
(3) Calculate the inductor ripple current (△IL). In steady state conditions, the inductor ripple
current increase, (△IL+), during the ON time and the current decrease, (△IL-), during the OFF
time must be equal.
IL TS
TOFF TON
ICRIT
△IL
T
ΔIL = 2 × ICRIT
(4) Calculate the minimum value of inductor use maximum input voltage. That is the worst case
condition because it gives the maximum △IL.
L ≥ [VIN(MAX ) - ILOAD × (R DS(ON) + R L) - VOUT ] × D(MIN )
ΔIL × fs
This formula can be simplified to
L ≥(VIN(MAX) - VOUT)×D(MIN)
ΔIL × fs
Rev01
- 11 -
Mar. 07, 2013
www.inno.com.tw
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet LA8509A.PDF ] | |
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