Fairchild SG6858DZ, SG6858TZ, SG6858TZ, SG6858DZ Schematic [ru]
September 2009
SG6858
Low-Cost, Green-Mode, PWM Controller for Flyback
Converters
SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters
Features
Green-Mode PWM
Supports the ”Blue Angel” Standard
Low Startup Current: 10µA (Maximum)
Low Operating Current: 2.5mA
Leading-Edge Blanking (LEB)
Constant Output Power Limit
Built-in Synchronized Slope Compensation
Current-Mode Operation
Cycle-by-Cycle Current Limiting
Under-Voltage Lockout (UVLO)
Programmable PWM Frequency
V
Over-Voltage Protection with Auto-Restart
DD
Gate Output Voltage Clamped at 17V
Few External Components Required
SSOT-26 and DIP-8 Packages Available
Applications
Battery chargers for cellular phones, cordless
phones, PDAs, digital cameras, and power tools
Power adapters for ink jet printers, video game
consoles, and portable audio players
Open-frame SMPS for TV/DVD standby and other
auxiliary supplies, home appliances, PC 5V
standby power, and consumer electronics
Replacements for linear transformers and RCC
SMPS
Offline High Brightness (HB) LED drivers
Description
This highly integrated PWM controller provides several
special enhancements designed to meet the low
standby-power needs of low-power SMPS. To minimize
standby power consumption, the proprietary greenmode function provides off-time modulation to linearly
decrease the switching frequency under light-load
conditions. This green-mode function enables the
power supply to meet even the strictest power
conservation requirements.
The BiCMOS fabrication process enables reducing the
startup current to 10µA and the operating current to
2.5mA. To further improve power conservation, a large
startup resistance can be used. Built-in synchronized
slope compensation ensures the stability of peakcurrent-mode control. Proprietary internal compensation
provides a constant output power limit over a universal
AC input range (90V
current limiting ensures safe operation even during
short circuits.
To protect the external power MOSFET from being
damaged by supply over voltage, the output driver is
clamped at 17V. SG6858 controllers can improve the
performance and reduce the production cost of power
supplies. The SG6858 replaces linear and RCC-mode
power adapters. It is available in 8-pin DIP and 6-pin
SSOT-26 packages.
to 264VAC). Pulse-by-pulse
AC
Ordering Information
Part Number Operating Temperature Range
SG6858TZ -40 to +125°C RoHS 6-Pin SSOT-26 Tape & Reel
SG6858DZ -40 to +125°C RoHS 8-Pin DIP-8 Tube
For Fairchild’s definition of Eco Status, please vis i t : http://www.fairchildsemi.com/company/green/rohs_green.html.
© 2008 Fairchild Semiconductor Corporation www.fairchildsemi.com
SG6858 • Rev. 1.2.4
Eco Status
Package Packing Method
Typical Application
SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters
L
AC Input
N
EMI
Filter
Bridge
Rectifier
Diode
+ +
C
R
Bulk
Start
C
VDD
5
R
D
VDD
+
C
SN
SN
N
P
D
SN
N
A
C
R
SN2
SN2
VO+
D
R
N
S
C
C
O2
O1
ZD
O
VO-
VDD
3
RI
R
RI
2
C
FB
FB
SG6858
SENSE
GND
1
GATE
6
4
R
G
R
C
LF
LF
R
SEN SE
R
d
R
1
PC817
C
R
F
F
TL431
R
2
Figure 1. Typical Application
Block Diagram
25V
VDD
5(2)
SOT(DIP)
OVP
Internal
UVL O
16.5V/11.5V
BIAS
GND
1(8)
OSC S
Green
Mode
Contro lle r
RI
3(5)
Q
R
Figure 2. Block Diagram
Soft
Dri ver
V
limitramp
+
Slope
Comp ensa tion
3R
2R
V
DD
Blanking
Cir cuit
5V
6(1)
4(4)
2(7)
GATE
SENSE
FB
© 2008 Fairchild Semiconductor Corporation www.fairchildsemi.com
SG6858 • Rev. 1.2.4 2
Marking Information
Figure 3. SSOT-26
Figure 4. DIP-8
SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters
XXX:AAI=SG6858
TT: Die run code
●: Year code
— : Week code
F: Fairchild Logo
Z: Assembly Plant Code
X: Year Code
Y: Week Code
TT: Die Run Code
T: N=DIP
P: Y=Green Package
M: Manufacture flow code
Pin Configuration
GND
FB
RI
1
2
3
SOT -26
GAT E
6
5
VDD
E
SENS
4
Figure 5. Pin Configurations
GATE
SENSE
Pin Definitions
Pin #
DIP-8 SSOT-26
1 6 GATE Totem-pole output driver for the power MOSFET.
2 5 VDD Power supply.
3 NC No connection.
4 4 SENSE
5 3 RI
6 NC No connection.
7 2 FB
8 1 GND Ground.
Name Description
Current sense. This pin senses the voltage across a resistor. When the voltage
reaches the internal threshold, PWM output is disabled. This activates over-current
protection. This pin provides current amplitude information for current-mode control.
A resistor connected from the RI pin to ground generates a constant current source.
This current is used to charge an internal capacitor to determine the switching
frequency. Increasing the resistance reduces the amplitude of the current source
and reduces the switching frequency. A 95kΩ resistor, R
current, I
Feedback. The FB pin provides the output voltage regulation signal, and feedback to
the internal PWM comparator, so the PWM comparator can control the duty cycle.
and a 70kHz switching frequency.
I,
VDD
NC
1
2
3
4
DIP-8
results in a 50µA constant
I,
8
GND
7
FB
6
NC
RI
5
© 2008 Fairchild Semiconductor Corporation www.fairchildsemi.com
SG6858 • Rev. 1.2.4 3
SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters
Absolute Maximum Ratings
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be
operable above the recommended operating conditions and stressing the parts to these levels is not recommended.
In addition, extended exposure to stresses above the recommended operating conditions may affect device
reliability. The absolute maximum ratings are stress ratings only. All voltage values, except differential voltages, are
given with respect to GND pin.
Symbol Parameter Min. Max. Unit
VDD Supply Voltage 30 V
VFB Input Voltage to FB Pin -0.3 7.0 V
V
Input Voltage to SENSE Pin -0.3 7.0 V
SENSE
R
Thermal Resistance (Junction-to-Case)
ΘJC
DIP 82.5
TJ Operating Junction Temperature -40 +125 °C
SSOT
T
Storage Temperature Range -55 +150 °C
STG
TL Lead Temperature, Wave Soldering, 10 Seconds 260 °C
ESD Electrostatic Discharge Capability
Human Body Model, JESD22-A114 3.0
Machine Model, JESD22-A115 0.2
208.4
°C/W
kV
Recommended Operating Conditions
The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended
operating conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not
recommend exceeding them or designing to Absolute Maximum Ratings.
Symbol Parameter Min. Max. Unit
V
TA Operating Ambient Temperature -40 +125 °C
DC Supply Voltage 22 V
DD
© 2008 Fairchild Semiconductor Corporation www.fairchildsemi.com
SG6858 • Rev. 1.2.4 4
SG6858 — Low-Cost, Green-Mode, PWM Controller for Flyback Converters
Electrical Characteristics
VDD=15V, TA=-40°C ~+125°C (TA= TJ), unless otherwise specified.
Symbol Parameter Test Condition Min. Typ. Max. Unit
VDD Section
V
Continuously Operating Voltage 22 V
DD-OP
V
Turn-On Threshold Voltage 15.5 16.5 17.5 V
DD-ON
V
Turn-Off Voltage 10.5 11.5 12.5 V
DD-OFF
I
Startup Current VDD=V
DD-ST
I
Operating Supply Current
DD-OP
V
VDD Over-Voltage Protection Level 23 25 26 V
DD-OVP
t
D-VDDOVP
V
VDD OVP Debounce Time 50 125 200 µsec
VDD Low Threshold Voltage to Exit Green
DD-G OFF
VDD=15V, GATE with
1nF to GND
V
Off Mode
Feedback Input Section
AV FB Input to Current Comparator Attenuation 2/5 V/V
ZFB Input Impedance 5 kΩ
V
FB Pin Open High Voltage 4.5 5.0 5.5 V
FB-OPEN
V
Green Mode Entry FB Voltage 2.85 V
FB-N
V
Green Mode Ending FB Voltage 2.20 V
FB-G
SG Green Mode Modulation Slope RI=95kΩ 75 Hz/mV
– 0.1V 10 15 µA
DD-ON
2.5 3.5 mA
V
DD-OFF
+ 0.95
+ 1.10
DD-OFF
V
DD-OFF
+ 1.25
V
Current Sense Section
Z
SENSE
tPD Delay to Output 60 110 ns
V
STHFL
V
STHVA
t
LEB
DCY
Input Impedance 10 kΩ
Flat Threshold Voltage for Current Limit 0.96 V
Valley Threshold Voltage for Current Limit 0.75 0.80 0.85 V
Leading-Edge Blanking Time 240 300 360 ns
Duty Cycle of SAW Limit
SAW
Maximum Duty
Cycle
45 %
Oscillator Section
f
OSC
f
OSC-G
fDV Frequency Variation vs. VDD Deviation VDD=13.5V to 22V 0 0.02 2.00 %
fDT
Frequency RI=95kΩ 65 70 75 kHz
Green Mode Frequency RI=95kΩ 22 kHz
Frequency Variation vs. Temperature
Deviation
TA=-40°C ~+125°C 2 %
Output Section
DCY
V
GATE-L
V
GATE-H
tR Rising Time VDD=13.5V, CL=1nF 100 170 240 ns
tF Falling Time VDD=13.5V, CL=1nF 35 55 75 ns
V
GATE-CLAMP
Maximum Duty Cycle 70 75 80 %
MAX
Output Voltage Low VDD=15V, IO=20mA 1.5 V
Output Voltage High
VDD=13.5V,
I
=20mA
O
8 V
Output Clamp Voltage VDD=13.5V, TA=25°C 16 17 18 V
© 2008 Fairchild Semiconductor Corporation www.fairchildsemi.com
SG6858 • Rev. 1.2.4 5
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