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PDF FAN7554 Data sheet ( Hoja de datos )
| Número de pieza | FAN7554 | |
| Descripción | Versatile PWM Controller | |
| Fabricantes | Fairchild Semiconductor | |
| Logotipo |  |
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FAN7554
Versatile PWM Controller
www.fairchildsemi.com
Features
• Current mode control
• Pulse by pulse current limiting
• Low external components
• Under voltage lockout(UVLO): 9V/15V
• Stand-by current: typ. 100uA
• Power saving mode current: typ. 200uA
• Operating current: typ. 7mA
• Soft start
• On/off control
• Over load protection(OLP)
• Over voltage protection(OVP)
• Over current protection(OCP)
• Over current limit(OCL)
• Operating frequency up to 500kHz
• 1A totem-pole output current
Applications
• Off-Line & DC-DC converter
Description
The FAN7554 is a fixed frequency current mode PWM
controller. It is specially designed for off-line and DC to DC
converter applications with minimal external components.
These integrated circuits feature a trimmed oscillator for
precise duty cycle control, a temperature compensated
reference, an ON/OFF control, a high gain error amplifier, a
current sensing comparator, and a high current totem-pole
output. The FAN7554 has various protection functions such
as an over load protection, an over current protection, and
the over voltage protection, which include built-in auto
restart circuit. The FAN7554 is available in the 8-DIP
package as well as the 8-SOP package.
8-DIP
1
8-SOP
1
©2003 Fairchild Semiconductor Corporation
Rev. 1.0.3
1 page  
Electrical Characteristics (Continued)
(Ta = 25°C, Vcc=16V, Rt =10kΩ, Ct = 3.3nF unless otherwise specified)
Parameter
Symbol
Conditions
<TOTAL STAND-BY CURRENT SECTION>
Start-up current
IST
-
Operating supply current
IOP
-
Off State current
IOFF VFB<VTH(FB),VS/S<VOFF
Note:
1. These parameters, although guaranteed, are not 100% tested in production.
FAN7554
Min. Typ. Max. Unit
- 0.1 0.2 mA
- 7 10 mA
- 0.2 0.4 mA
5
5 Page 
FAN7554
Vfb
6V
Slope (dv/dt) = 5uA / Cfb
Shutdown start point
3V
t1
t2
Figure 17-B . Delayed Shutdown & Feedback Waveform
t
Gate Driver
The gate drive circuit has the totem-pole output configuration. The output has 1A peak current and 200mA average current
drive ability.
7 DRAIN
Clock
OUT
Q6
Shutdown
FAN7554
Figure 18. Gate Drive Circuit
ON/OFF Control
The FAN7554 is able to use the feedback pin for ON/OFF control by placing NPN transistor between the cathode of the
KA431 and ground as shown in figure 19. When the transistor turns on, the current flows through the photo diode and
saturates the photo transistor. As a result, the feedback voltage is dropped to zero. When the feedback voltage is below 0.3V,
the soft start voltage starts to discharge by connecting the internal resistor 1kΩ in parallel with the external capacitor Cs. When
the soft start voltage becomes less than 1.5V, all the blocks in the FAN7554 are turned off , with the exceptions of the UVLO
block and ON/OFF control block. The operation current is about 200uA. So the stand-by power is reduced and SMPS
efficiency is improved. When the feedback voltage exceeds 0.3V, the FAN7554 normally operates by turning on Vref block.
11
11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet FAN7554.PDF ] | |
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