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PDF FAN7621 Data sheet ( Hoja de datos )

Número de pieza FAN7621
Descripción PFM Controller
Fabricantes Fairchild Semiconductor 
Logotipo Fairchild Semiconductor Logotipo



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No Preview Available ! FAN7621 Hoja de datos, Descripción, Manual

www.DataSheet4U.com
February 2009
FAN7621
PFM Controller for Half-Bridge Resonant Converters
Features
ƒ Variable Frequency Control with 50% Duty Cycle
for Half-bridge Resonant Converter Topology
ƒ High Efficiency through Zero Voltage Switching (ZVS)
ƒ Fixed Dead Time (350ns)
ƒ Up to 300kHz Operating Frequency
ƒ Pulse Skipping for Frequency Limit (Programmable)
at Light-Load Condition
ƒ Remote On/Off Control using CON Pin
ƒ Protection Functions: Over-Voltage Protection
(OVP), Overload Protection (OLP), Over-Current
Protection (OCP), Abnormal Over-Current Protection
(AOCP), Internal Thermal Shutdown (TSD)
Applications
ƒ PDP and LCD TVs
ƒ Desktop PCs and Servers
ƒ Adapters
ƒ Telecom Power Supplies
ƒ Video Game Consoles
Description
The FAN7621 is a pulse frequency modulation controller
for high-efficiency half-bridge resonant converters.
Offering everything necessary to build a reliable and
robust resonant converter, the FAN7621 simplifies
designs and improves productivity, while improving
performance. The FAN7621 includes a high-side gate-
drive circuit, an accurate current controlled oscillator,
frequency limit circuit, soft-start, and built-in protection
functions. The high-side gate-drive circuit has a
common-mode noise cancellation capability, which
guarantees stable operation with excellent noise
immunity. Using the zero-voltage-switching (ZVS)
technique dramatically reduces the switching losses and
efficiency is significantly improved. The ZVS also
reduces the switching noise noticeably, which allows a
small-sized Electromagnetic Interference (EMI) filter.
The FAN7621 can be applied to various resonant
converter topologies; such as series resonant, parallel
resonant, and LLC resonant converters.
Related Resources
AN4151 — Half-bridge LLC Resonant Converter Design
using FSFR-series Fairchild Power Switch (FPSTM)
Ordering Information
Part Number
FAN7621N
FAN7621SJ
FAN7621SJX
Operating
Junction
Temperature
-40°C ~ 130°C
Eco
Status
RoHS
Package
16-DIP
16-SOP
16-SOP
Packaging Method
Tube
Tube
Tape & Reel
For Fairchild’s definition of “green” Eco Status, please visit: http://www.fairchildsemi.com/company/green/rohs_green.html.
© 2009 Fairchild Semiconductor Corporation
FAN7621 • Rev. 1.0.0
www.fairchildsemi.com

1 page




FAN7621 pdf
www.DataSheet4U.com
Electrical Characteristics
TA=25°C and LVCC=17V unless otherwise specified.
Symbol
Parameter
Test Conditions
Supply Section
ILK Offset Supply Leakage Current
IQHVCC Quiescent HVCC Supply Current
IQLVCC Quiescent LVCC Supply Current
IOHVCC
Operating HVCC Supply Current
(RMS Value)
IOLVCC
Operating LVCC Supply Current
(RMS Value)
HVCC=VCTR
(HVCCUV+) - 0.1V
(LVCCUV+) - 0.1V
fOSC=100kHz, VCON > 0.6V,
CLoad=1nF
No Switching, VCON < 0.4V
fOSC=100kHz, VCON > 0.6V,
CLoad=1nF
No Switching, VCON < 0.4V
UVLO Section
LVCCUV+
LVCCUV-
LVCCUVH
HVCCUV+
HVCCUV-
HVCCUVH
LVCC Supply Under-Voltage Positive Going Threshold (LVCC Start)
LVCC Supply Under-Voltage Negative Going Threshold (LVCC Stop)
LVCC Supply Under-Voltage Hysteresis
HVCC Supply Under-Voltage Positive Going Threshold (HVCC Start)
HVCC Supply Under-Voltage Negative Going Threshold (HVCC Stop)
HVCC Supply Under-Voltage Hysteresis
Oscillator & Feedback Section
VCONDIS
VCONEN
VRT
fOSC
DC
Control Pin Disable Threshold Voltage
Control Pin Enable Threshold Voltage
V-I Converter Threshold Voltage
Output Oscillation Frequency
RT=5.2kΩ
Output Duty Cycle
fSS
Internal Soft-Start Initial Frequency
fSS=fOSC+40kHz, RT=5.2kΩ
tSS Internal Soft-Start Time
Output Section
Isource
Isink
tr
tf
VHOH
VHOL
VLOH
VLOL
Peak Sourcing Current
Peak Sinking Current
Rising Time
Falling Time
High Level of High-Side Gate Driving
Signal (VHVCC-VHO)
Low Level of High-Side Gate Driving
Signal
High Level of High-Side Gate Driving
Signal (VLVCC-VLO)
Low Level of High-Side Gate Driving
Signal
HVCC=17V
HVCC=17V
CLoad=1nF, HVCC=17V
IO=20mA
Min.
13.0
10.2
8.2
7.8
0.36
0.54
1.5
94
48
2
250
460
Typ.
50
100
5
100
6
2
14.5
11.3
3.2
9.2
8.7
0.5
0.40
0.60
2.0
100
50
140
3
360
600
65
35
Max. Unit
50 μA
120 μA
200 μA
8 mA
200 μA
9 mA
4 mA
16.0
12.4
10.2
9.6
V
V
V
V
V
V
0.44 V
0.66 V
2.5 V
106 kHz
52 %
kHz
4 ms
mA
mA
ns
ns
1.0 V
0.6 V
1.0 V
0.6 V
© 2009 Fairchild Semiconductor Corporation
FAN7621 • Rev. 1.0.0
5
www.fairchildsemi.com

5 Page





FAN7621 arduino
www.DataSLhaetect4hU-M.coomde Protection: Once this protection is
triggered, switching is terminated and the gate output
signals remain off. The latch is reset only when LVCC is
discharged below 5V.
LV CC
7
11 / 14 V
+ LV CC good V REF
-
Internal
Bias
OCP
OLP
OVP
LV CC good
CON
20k
Auto-restart
protection
SQ
R -Q
F/F
Latch
protection
QS
-Q R
F/F
Shutdown
AOCP
TSD
LV CC < 5V
Figure 24. Protection Blocks
Current Sensing Using Resistor: FAN7621 senses
drain current as a negative voltage, as shown in Figure
25 and Figure 26. Half-wave sensing allows low power
dissipation in the sensing resistor, while full-wave
sensing has less switching noise in the sensing signal.
C DL
LVCC
HV CC
RT
HO
CON
CTR
V CS
CS
LO
SG PG
Rsense
I ds
I ds
V CS
Figure 25. Half-Wave Sensing
I ds
C DL
L VCC
HV CC
RT
HO
CON
CTR
V CS
CS
LO
SG PG
V CS
I ds Rsense
Figure 26. Full-Wave Sensing
Current Sensing Using Resonant Capacitor Voltage:
For high-power applications, current sensing using a
resistor may not be available due to the severe power
dissipation in the resistor. In that case, indirect current
sensing using the resonant capacitor voltage can be a
good alternative because the amplitude of the resonant
capacitor
current in
tvhoeltapgriema(Vrycrps-ipd)eis(Ipppr-po)paosrt:ional
to
the
resonant
V pp
Cr
=
I pp
p
2π fsCr
(6)
To minimize power dissipation, a capacitive voltage
divider is generally used for capacitor voltage sensing,
as shown in Figure 27.
CDL
LVCC
HV CC
RT
HO
CON
CTR
Ip
CS
SG
LO
PG
Csense
Vsense
CB
100
Cr
Ip
VCr
VCrp-p
Vsense
V pk
sense
V pp
Cr
=
CB
Csense+ C B
V pk
sense
2
= VCON
VCON
Vsensepk
Vsensepk
tDelay =RdCd
Figure 27. Current Sensing Using Resonant
Capacitor Voltage
5.1 Over-Current Protection (OCP): When the sensing
pin voltage drops below -0.6V, OCP is triggered and the
MOSFETs remain off. This protection has a shutdown
time delay of 1.5µs to prevent premature shutdown
during startup.
5.2 Abnormal Over-Current Protection: (AOCP): If the
secondary rectifier diodes are shorted, large current with
extremely high di/dt can flow through the MOSFET
before OCP or OLP is triggered. AOCP is triggered
without shutdown delay when the sensing pin voltage
drops below -0.9V. This protection is latch mode and
reset when LVCC is pulled down below 5V.
© 2009 Fairchild Semiconductor Corporation
FAN7621 • Rev. 1.0.0
11
www.fairchildsemi.com

11 Page







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