H6842S Datasheet PDF - Hi-Sincerity
| Part Number | H6842S | |
| Description | Novel Low Cost Green-Power PWM Controller | |
| Manufacturers | Hi-Sincerity | |
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HI-SINCERITY
MICROELECTRONICS CORP.
Spec. No. : IC200803
Issued Date : 2008.09.10
Revised Date :
Page No. : 1/6
H6842P / H6842S
Novel Low Cost Green-Power PWM Controller
Description
The H684 2 is a lo w startup cu rrent, lo w co st, curre n. mode PWM co ntroller with
8-Lead Plastic DIP-8
Package Code: P
Green-Power & burst- mode power-saving operation. The integrated functions such
as the leading-edge blanking of the current sensing, internal slope compensation
provide the users a high efficiency, low external component counts, and low cost
•
solution for A C/DC po wer app lications. The special Green-Power function provides
off-time modulation to linearly decrease the switching frequency under ight-load
conditions. And under zero-load conditions, the power supply enters burst-mode to
8-Lead Plastic SO-8
further reduce power consumption b y shutting off P WM output. When the output of
Package Code: S
power supply is short or over loaded, the FB voltage will increase, and if the FB
voltage is higher than 5.2V f or longer th an 56msec the PWM out put will be turned off.
A external NTC ressi tor connected from pin RT to ground can be applied to over- temperature protection. Pulse by
pulse current limit ensures a constant output current even under short circuit. PWM output will be disabled as long as
VDD exceeds a threshold. When internal latch circuit is us ed to latch-off the controller the latch wil be reset when
the power supply VDD is disabled
Features
• Low Cost, Green-Power Burst-Mode PWM
• Very Low Start-up Current ( about 7.5uA)
• Low Operating Current ( about 3.0mA)
• Current Mode Operation
• Under Voltage Lockout (UVLO)
• VDD Over Voltage Protection(OVP)
• programmable over-temperature protection
• Internal Latch Circuit(OTP,OVP)
• Built-in soft start with 1ms
• Soft Clamped gate output voltage 16.5V
• VDD over voltage protect 25.5V
• Cycle-by-cycle current limiting
• Output SCP (Short circuit Protection)
• Built-in Synchronized Slope ompensation
• Leading-edge blanking on Sense input
• Programmable PWM Frequency
• High-Voltage CMOS Process with ESD
• DIP-8 & SOP-8 Pb-Free Package
• Compatible with SG6842J&LD7552&
OB2269 & SG6841 & OB2268
Applications
• Power Adaptor
• Battery Charger Adapter
Ordering Information
Part Number
Description
H6842P
DIP-8, Pb-free in Tube
H6842S
SOP-8, Pb-free in Tube
H6842SA
SOP-8,Pb-free in T/R
• Open Frame Switching Power Supply
• LCD Monitor
H6842P, H6842S
HSMC Product Specification
http://www.Datasheet4U.com
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HI-SINCERITY
MICROELECTRONICS CORP.
Spec. No. : IC200803
Issued Date : 2008.09.10
Revised Date :
Page No. : 5/6
The turn-on/turn-off thresholds are fixed internally at 12.4V/16.5V. To enable a H6842 controller during start-up,
the hold-up capacitor must first be charged to 16.5V through the start-up resistor.
The hold-up capacitor will continue to supply VDD before energy can be delivered from the auxiliary winding of
the main transformer. VDD must not drop below 12.4V during this start-up process. This UVLO hysteresis window
ensures that the hold-up capacitor can adequately supply VDD during start-up.
Gate Output / Soft Driving
The H6842 output stage is a fast totem pole gate driver. Cross-conduction has been avoided to minimize heat
dissipation, increase efficiency, and enhance reliability. The output driver is clamped by an internal 18V Zener
diode in order to protect the power MOSFET transistors from any harmful over-voltage gate signals. A soft driving
waveform is implemented to minimize EMI.
Slope Compensation
The sensed voltage across the current sense resistor is used for peak-current-mode control and cycle-by-cycle
current limiting. The built-in slope compensation function improves power supply stability and prevents peak-current-
mode control from causing sub-harmonic oscillations. Within every switching cycle, the H6842 controller produces
a positively sloped, synchronized ramp signal
Constant Output Power Limit
When the SENSE voltage across the sense resistor RS reaches the threshold voltage, the output GATE drive
will be turned off following a small propagation delay TPD. This propagation delay will result in anadditional
current proportional to TPD*VIN/LP. The propagation delay is nearly constant regardless of th e input line voltage
VIN. Higher input line voltages will result in larger additional currents. Thus, under high input-line voltages the
output power limit will be higher than under low input-line voltages.
The output power limit variation can be significant over a wide range of AC input voltages. To compensate
for this, the threshold voltage is adjusted by the current IIN. Since the pin VIN is connected to the rectified input line
voltage through the start- up resistor, a higher line voltage will result in a higher current IIN through the pin VIN.
The thre shold voltage de creases if th e cu rrent I IN increases. A small threshold voltage will force the output
GATE drive to terminate earlier, thus reducing total PWM turn-on time, and m aking the output power equal to
to that of the low line input. This proprietary internal compensation feature ensures a constant output power limit
over a wide range of AC input voltages (90VAC to 264VAC)
VDD Over-voltage Protection
VDD over-voltage protection has been built in to prevent damage due to over voltage conditions. When the voltage
VDD exceeds the internal threshold due to abnormal conditions, PWM output will be turned off. Over-voltage
conditions are usually caused by open feedback loops.
Limited Power Control
The FB voltage will i ncrease every time the output of the power supply is shorted or over-loaded. If the FB
voltage rem ains hig her tha n a built-in threshold for longer than TLPS, PWM output will then be turned off. As
PWM output is turned off, the supply voltage VDD will also begin decreasing. When VDD goes bel ow the turn-off
threshold (eg, 12.4V) the controller will be totally shut down. VDD will be charged up to t he turn-on threshold
voltage of 16.5V through the start-up resistor untilPWM output is restarted. This protection feature will continue
To be activated as long as the over-loading condition persists. This will prevent the power supply from overheating
due to over loading conditions
Thermal Protection
An external NTC thermistor can be connected from the RT pin to ground. A fixed current IRT is sourced from the
RT pin. Because the impedance of the NTC will decrease at high temperatures, when the voltage of the RT pin
drops below 1.065V, PWM output will be disabled. The RT pin output current is related to the PWM frequency
programming resistor RI.
Noise Immunity
Noise from the current sense or the control signal may cause significant pulse width jitter, particularly in
continuous-conduction mode. Slope compensation helps alleviate this problem. Good placement and layout
practices should be followed. The designer should avoiding long PCB traces and component leads. Compensation
and filter components should be located near the H6842. Finally, increasing the power-MOS gate resistance is
advised.
H6842P, H6842S
HSMC Product Specification
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| Information | Total 6 Pages | |
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| Download | [ H6842S.PDF Datasheet ] | |
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