FSQ0765R datasheet(15/22 Pages) FAIRCHILD

Part #	FSQ0765R

Description	Green-Mode Fairchild Power Switch (FPS?? for Quasi-Resonant Operation - Low EMI and High Efficiency

Download	22 Pages

Scroll/Zoom	100%

Manufacturer	FAIRCHILD [Fairchild Semiconductor]

Direct Link	http://www.fairchildsemi.com

Logo

15 / 22 page

www.fairchildsemi.com

FSQ0565R, FSQ0765R Rev. 1.0.0

15

uses a sync signal instead of directly monitoring the

output voltage. If the sync signal exceeds 8V, an OVP is

triggered, shutting down the SMPS. To avoid undesired

triggering of OVP during normal operation, there are two

points considered, as depicted in Figure 32. The peak

voltage of the sync signal should be designed below 6V

and the spike of the SYNC pin must be as low as

possible to avoid getting longer than tOVP by decreasing

the leakage inductance shown at VCC winding coil.

Figure 32. OVP Triggering

4.5 Thermal Shutdown with Hysteresis (TSD): The

SenseFET and the control IC are built in one package.

This makes it easy for the control IC to detect the

abnormally high temperature of the SenseFET. If the

temperature exceeds approximately 140°C, the thermal

shutdown triggers IC shutdown. The IC recovers its

operation when the junction temperature decreases

60°C from TSD temperature and VCC reaches start-up

voltage (Vstart).

5. Soft-Start: The FPS has an internal soft-start circuit

that increases PWM comparator inverting input voltage

with the SenseFET current slowly after it starts up. The

typical soft-start time is 15ms. The pulse width to the

power switching device is progressively increased to

establish the correct working conditions for transformers,

inductors, and capacitors. The voltage on the output

capacitors is progressively increased with the intention of

smoothly establishing the required output voltage. This

mode helps prevent transformer saturation and reduces

stress on the secondary diode during start-up.

6. Burst Operation: To minimize power dissipation in

standby mode, the FPS enters burst-mode operation. As

the load decreases, the feedback voltage decreases. As

shown in Figure 33, the device automatically enters

burst-mode when the feedback voltage drops below

VBURL (350mV). At this point, switching stops and the

output voltages start to drop at a rate dependent on

standby current load. This causes the feedback voltage

to rise. Once it passes VBURH (550mV), switching

resumes. The feedback voltage then falls and the

process repeats. Burst-mode operation alternately

enables and disables switching of the power SenseFET,

thereby reducing switching loss in standby mode.

Figure 33. Waveforms of Burst Operation

7. Switching Frequency Limit: To minimize switching

loss and Electromagnetic Interference (EMI), the

MOSFET turns on when the drain voltage reaches its

minimum value in quasi-resonant operation. However,

this causes switching frequency to increases at light load

conditions. As the load decreases or input voltage

increases, the peak drain current diminishes and the

switching frequency increases. This results in severe

switching losses at light-load condition, as well as

intermittent switching and audible noise. These problems

create limitations for the quasi-resonant converter

topology in a wide range of applications.

To overcome these problems, FSQ-series employs a

frequency-limit function, as shown in Figures 34 and 35.

Once the SenseFET is turned on, the next turn-on is

prohibited during the blanking time (tB). After the

blanking time, the controller finds the valley within the

detection time window (tW) and turns on the MOSFET, as

shown in Figures 34 and Figure 35 (Cases A, B, and C).

V

Vcc_coil &VCC

V

sync

V

OVP(8V)

V

CC

V

Vcc_coil

V

CLAMP

V

SH2 (4.8V)

V

DC

N

pri

N

Vcc

Absolue max V

CC(20V)

t

OVP

t

OVP

Improper OVP triggering

FSQ0765RRev.00

V

FB

V

DS

0.35V

0.55V

I

DS

V

O

V

O

set

time

Switching

disabled

t1

t2 t3

Switching

disabled

t4

FSQ0765R Rev.00

Similar Part No. - FSQ0765R

Manufacturer	Part #	Datasheet	Description
Fairchild Semiconductor	FSQ0765R	2Mb / 22P	Green-Mode Fairchild Power Switch (FPS?? for Quasi-Resonant Operation - Low EMI and High Efficiency
	FSQ0765RQ	3Mb / 19P	Green-Mode Fairchild Power Switch
	FSQ0765RQWDTU	3Mb / 19P	Green-Mode Fairchild Power Switch
	FSQ0765RS	3Mb / 19P	Green-Mode Fairchild Power Switch (FPS) for Quasi-Resonant Operation - Low EMI and High Efficiency
	FSQ0765RSWDTU	3Mb / 19P	Green-Mode Fairchild Power Switch (FPS) for Quasi-Resonant Operation - Low EMI and High Efficiency

More results

Similar Description - FSQ0765R

Manufacturer	Part #	Datasheet	Description
Fairchild Semiconductor	FSQ0565R	2Mb / 22P	Green-Mode Fairchild Power Switch (FPS?? for Quasi-Resonant Operation - Low EMI and High Efficiency
	FSQ0465RU	3Mb / 22P	Green-Mode Fairchild Power Switch (FPS) for Quasi-Resonant Operation - Low EMI and High Efficiency
	FSQ0365RN	1Mb / 19P	Green Mode Fairchild Power Switch (FPS) for Quasi-Resonant Operation - Low EMI and High Efficiency
	FSQ0465RB	3Mb / 23P	Green-Mode Fairchild Power Switch (FPS) for Quasi-Resonant Operation - Low EMI and High Efficiency
	FSQ0765RS	3Mb / 19P	Green-Mode Fairchild Power Switch (FPS) for Quasi-Resonant Operation - Low EMI and High Efficiency
	FSQ0565RQ	2Mb / 23P	Green-Mode Fairchild Power Switch (FPS) for Quasi-Resonant Operation - Low EMI and High Efficiency
	FSQ0465RS	3Mb / 23P	Green-Mode Fairchild Power Switch (FPS) for Quasi-Resonant Operation - Low EMI and High Efficiency
	FSQ510	707Kb / 15P	Green Mode Fairchild Power Switch (FPS) for Quasi-Resonant Converter - Low EMI and High Efficiency
ON Semiconductor	FSQ0565RS	2Mb / 24P	Green-Mode Power Switch for Quasi-Resonant Operation - Low EMI and High Efficiency October-2017, Rev. 3
Fairchild Semiconductor	FSCQ0765RT	726Kb / 24P	Green Mode Fairchild Power Switch (FPS) for Quasi-Resonant Switching Converter

More results

FSQ0765R Datasheet(PDF) 15 Page - Fairchild Semiconductor

FSQ0765R Datasheet(HTML) 15 Page - Fairchild Semiconductor

Similar Part No. - FSQ0765R

Similar Description - FSQ0765R

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Datasheet Download

Link URL