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PDF SD46520 Data sheet ( Hoja de datos )
| Número de pieza | SD46520 | |
| Descripción | 400KHZ 2A STEP-DOWN DC-DC CONVERTER | |
| Fabricantes | Silan | |
| Logotipo |  |
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SD46520
400KHZ 2A STEP-DOWN DC-DC CONVERTER
DESCRIPTION
The SD46520 is a step-down PWM control converter with a built-in
internal power MOSFET. It achieves 2A continuous output current
over a wide input supply range with excellent load and line
regulation.
Current mode operation provides fast transient response and eases
loop stabilization.
It provides cycle-by-cycle current limiting and thermal shutdown. In
shutdown mode, the current is only 23μA.
SOP-8-225-1.27
FEATURES
* 2A output current
* 0.2Ω internal power MOSFET
* Stable with low ESR output ceramic capacitor
* Up to 95% conversion efficiency
* shutdown mode
* 400kHz fixed frequency
* Thermal shutdown
* Cycle-by-cycle over current protection
* 4.75－18V input voltage range
* 1.22－16V output voltage range
* Programmable under voltage control
ORDERING INFORMATION
Device
Package
Seal
SD46520 SOP-8-225-1.27 SD46520
APPLICATIONS
* Distributed power system
* Battery charger
* TFT LCD Monitors
* Portable DVD
* Set-Top Box
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
Http://www.silan.com.cn
REV:1.0 2009.04.07
Page 1 of 8
1 page  
SD46520
higher than 2.495V, the chip works normally.
Short protection
When the output voltage is short connected to the ground, FB feedback voltage is pulled down to the ground, and
the oscillator frequency will decrease to 50kHz from normal 400kHz, which also decreases the inductor current
average value, that is the output current is decreased.
APPLICATION NOTE
Output voltage setting
As right figure shows, the output voltage is determined by the feedback
resistors ratio of R1 and R2. Generally, R2＝10KΩ, R1 is decided by:
R1=R2.(VO/1.22-1).
Inductor selection
When output current is large, the regulator is working under continuous
current mode that is inductor current is continuous and will not
decrease to zero. The inductor value will affect the ripple of inductor current, and the relationship between them
is as follows:
L
=
VO ⋅(VI − VO )
VI ⋅ fS ⋅ ΔI
.
Where, VI is input voltage, VO is output voltage, fs is on-off frequency, ΔI is the peak-peak value of inductor
current ripple. In general, ΔI is no larger than 30% of the maximum output current, thus to decide the inductor
value.
At the same time, the peak inductor current should be less than 2.4A, the value is decided by:
ILMAX
= IO
+
1
2
⋅
ΔIL
= IO
+
1
2
⋅
VO ⋅(VI − VO )
VI ⋅ fS ⋅L
.
Input capacitor selection
The input current of step-down DC-DC is not successive, an additional input capacitor CI is needed to keep input
voltage stable. The input capacitor should be low ESR, and ceramic capacitor is the best choice, tantalum
capacitor or low ESR electrolytic capacitor is all right. The input capacitor value should be larger than 10μF.
Output capacitor selection
The output capacitor CO is decided by the ripple requirement of output voltage. The output voltage ripple is
decided by:
ΔVO
=
ΔIL (ESR
+
⋅1
8fS ⋅ CO
)
.
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
Http://www.silan.com.cn
REV:1.0 2009.04.07
Page 5 of 8
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet SD46520.PDF ] | |
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