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PDF FAN6862 Data sheet ( Hoja de datos )
| Número de pieza | FAN6862 | |
| Descripción | Highly Integrated Green-Mode PWM Controller | |
| Fabricantes | Fairchild Semiconductor | |
| Logotipo |  |
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September 2009
FAN6862
Highly Integrated Green-Mode PWM Controller
Features
Low Startup Current: 8µA
Low Operating Current in Green Mode: 3mA
Peak-Current Mode Operation with Cycle-by-Cycle
Current Limiting
PWM Frequency Continuously Decreasing with
Burst Mode at Light Loads
VDD Over-Voltage Protection (OVP)
Constant Output Power Limit (Full AC Input Range)
Internal Latch Circuit for OVP, OTP
Fixed PWM Frequency (65KHz) with Frequency
Hopping
Feedback Open-Loop Protection with 56ms Delay
Soft Start Time: 4ms
400mA Driving Capability
Applications
www.DataShGeeent4eUr.aclo-pmurpose switch-mode power supplies and
flyback power converters, including:
Power Adapters
Open-Frame SMPS
SMPS with Surge-Current Output, such as for
Printers, Scanners, and Motor Drivers
Description
A highly integrated PWM controller, FAN6862 provides
several features to enhance the performance of flyback
converters. To minimize standby power consumption, a
proprietary green-mode function provides off-time
modulation to continuously decrease the switching
frequency under light-load conditions. Under zero-load
conditions, the power supply enters burst-mode, which
completely shuts off PWM output. Output restarts just
before the supply voltage drops below the UVLO lower
limit. This green-mode function enables power supplies
to meet international power conservation requirements.
The FAN6862 is designed for SMPS and integrates a
frequency-hopping function that helps reduce EMI
emission of a power supply with minimum line filters.
The built-in synchronized slope compensation is
proprietary sawtooth compensation for constant output
power limit over universal AC input range. The gate
output is clamped at 18V to protect the external
MOSFET from over-voltage damage.
Other protection functions include VDD over-voltage
protection and over-temperature protection. For over-
temperature protection, an external NTC thermistor can
be applied to sense the ambient temperature. When
VDD OVP or OTP is activated, an internal latch circuit
latches off the controller.
Part Number
FAN6862TY
OVP
Latch
OTP
OLP
Latch Auto Restart
Ordering Information
Part Number
FAN6862TY
Operating Temperature Range
-40 to +105°C
Eco Status Package Packing Method
Green
6-Pin SSOT-26
Tape & Reel
For Fairchild’s definition of Eco Status, please visit: http://www.fairchildsemi.com/company/green/rohs_green.html.
© 2009 Fairchild Semiconductor Corporation
FAN6862 • Rev. 1.0.1
www.fairchildsemi.com
1 page  
Electrical Characteristics
VDD = 15V and TA = 25°C unless otherwise noted.
Symbol
Parameter
Test Condition
VDD Section
VDD-OP
VDD-ON
VDD-OFF
VDD-OVP
VDD-LH
IDD-ST
IDD-OP
IDD-BM
VDD-OVP
tD-VDDOVP
IDD-LH
Continuously Operating Voltage
Turn-on Threshold Voltage
Turn-off Voltage
VDD Over-Voltage Protection (Latch-Off)
Threshold voltage for Latch-Off release
Startup Current
Normal Operating Supply Current
Green-Mode Operating Supply Current
VDD Over-Voltage Protection
VDD OVP Debounce Time
Latch-Off Holding Current
VDD-ON–0.16V
CL=1nF
GATE open, VFB=VFB-G
VDD=5V
Feedback Input Section
AV
Input-Voltage to Current-Sense
Attenuation
ZFB
VFB-OPEN
VFB-OLP
Input Impedance
FB Pin Open Voltage
Threshold Voltage for Open-Loop
Protection
tD-OLP
Open-Loop Protection Delay Time
Current Sense Section
tPD Delay to Output
tLEB Leading-Edge Blanking Time
VSTHFL Flat Threshold Voltage for Current Limit
www.DataSheeVt4SUT.HcVoAm Valley Threshold Voltage for Current Limit
VSLOPE Slope Compensation
tSOFT-START Period During Startup time
Oscillator Section
Duty>51%
Duty=0%
Duty=DCYMAX
Center Frequency
fOSC Normal PWM Frequency
Hopping Range
Hopping Range
thop-1
thop-3
fOSC-G
VFB-N
Hopping Period 1
Hopping Period 3
Green Mode Minimum Frequency
FB Threshold Voltage For Frequency
Reduction
VFB≥VFB-N
VFB=VFB-G
VFB-G
VFB-ZDC
fDV
fDT
FB Voltage at fOSC-G
FB Threshold Voltage for Zero Duty
Frequency Variation vs. VDD Deviation
Frequency Variation vs. Temperature
Deviation
VDD=11.5V to 20V
TA= -40 to +105°C
© 2009 Fairchild Semiconductor Corporation
FAN6862 • Rev. 1.0.1
5
Min. Typ. Max. Unit
24 V
15
16 17
V
7.5 8.5 9.5 V
24
25 26
V
3 45V
8 30 μA
3 4 mA
2.5 mA
24
25 26
V
30 50 μs
40 65 μA
1/4 1/3.5 1/3 V/V
5.5 kΩ
5.0 5.2 5.4 V
4.3 4.6 4.9 V
53 56 60 ms
100 250 ns
270 360
ns
0.5 V
0.44 V
0.273
V
4 ms
VFB>VFB-N
VFB≥VFB-N
VFB=VFB-G
62
4.4
11.5
22.5
2.2
2.1
1.7
0 0.02
65
±4.2
±2.9
2.00
2
68
ms
ms
kHz
V
V
V
%
%
Continued on the following page…
www.fairchildsemi.com
5 Page 
Protections
Self-protective functions include VDD Over-Voltage
Protection (OVP), Open-Loop / Overload Protection
(OLP), Over-Current Protection (OCP), Short-Circuit
Protection, and Over-Temperature Protection (OTP).
OLP, OCP, and SCP are auto-restart mode protections;
while OVP and OTP are latch-mode protections.
Auto-Restart Mode Protection: Once a fault condition
is detected, switching is terminated and the MOSFET
remains off. This causes VDD to fall because no more
power is delivered from auxiliary winding. When VDD
falls to VDD-OFF (8.5V), the protection is reset and the
operating current reduces to startup current, which
causes VDD to rise. FAN6862 resumes normal operation
when VDD reaches VDD-ON (16V). In this manner, the
auto-restart can alternately enable and disable the
switching of the MOSFET until the fault condition is
eliminated (see Figure 25).
Latch-Mode Protection: Once this protection is
triggered, switching is terminated and the MOSFET
remains off. The latch is reset only when VDD is
discharged below 4V by unplugging AC power line.
VDS
Power
On
Protection Triggers
Fault Removed
Open-Loop / Over-Load Protection (OLP)
When the upper branch of the voltage divider for the
shunt regulator (KA431 shown) is broken, as shown in
Figure 26, no current flows through the opto-coupler
transistor, which pulls up the feedback voltage to 5.2V.
When the feedback voltage is above 4.6V longer than
56ms, OLP is triggered. This protection is also triggered
when the SMPS output drops below the nominal value
longer than 56ms due to the overload condition.
VFB 5.2V
VFB-OLP (4.6V)
VDD
16V
8.5V
www.DataSheet4U.com
Operating Current
3mA
8uA
Normal
Operation
Fault
Situation
Normal
Operation
Figure 25. Auto Restart Operation
Over-Current Protection (OCP)
FAN6862 has over-current protection thresholds. It is
for pulse-by-pulse current limit, which turns off MOSFET
for the remainder of the switching cycle when the
sensing voltage of MOSFET drain current reaches the
threshold. The other threshold is for the over-current
protection, which shuts down the MOSFET gate when
the sensing voltage of MOSFET drain current is above
the threshold longer than the shutdown delay (56ms).
OLP Shutdown Delay Time
OLP Triggers
Figure 26. OLP Operation
VDD Over-Voltage Protection (OVP)
VDD over-voltage protection prevents IC damage caused
by over voltage on the VDD pin. The OVP is triggered
when VDD reaches 25V. A debounce time (typically
30µs) prevents false triggering by switching noise.
Over-Temperature Protection (OTP)
The OTP circuit is composed of current source and
voltage comparators. Typically, an NTC thermistor is
connected between the RT and GND pins. Once the
voltage of this pin drops below a threshold of 1.0V,
PWM output is disabled after tDOTP debounce time. If
this pin drops below 0.7V, it triggers the latch-off
protection immediately after tDOTP2 debounce time.
© 2009 Fairchild Semiconductor Corporation
FAN6862 • Rev. 1.0.1
11
www.fairchildsemi.com
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet FAN6862.PDF ] | |
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