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PDF ( 数据手册 , 数据表 ) GR8837A

零件编号 GR8837A
描述 Green-Mode PWM Controller
制造商 Grenergy
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GR8837A 数据手册, 描述, 功能
Preliminary GR8837A
Green-Mode PWM Controller with Latch Protection
Features
Current mode control
Standby power below 100mW
Under-voltage lockout (UVLO)
Non-audible-noise green-mode control
65KHz switching frequency
Internal leading-edge blanking
Internal slope compensation
Internal soft start
Gate output voltage clamp
Jitter and soft driving for reducing EMI
External OVP Latch off mode
External OTP Latch off mode
Over-load protection (OLP)-Hiccup
300mA driving capability
Application
Switching AC/DC Adapter
Battery Charger
Open frame SMPS
Description
The GR8837A is a highly-integrated, low startup
current, current mode PWM controller with
green-mode function. This function enables the
power supply to easily meet even the strictest
power conservation requirements. The integrated
functions also include the leading-edge blanking
of the current sensing, internal slope com-
pensation, and soft start. OLP, OCP. The RTL pin
latch function by injecting a high over3.5V to
provide OVP latch off and low below 1V to provide
OTP latch off protection. To protect the external
power MOSFET from being damaged by supply
over voltage, the GR8837A OUT pin voltage is
clamped to about 13V.
The GR8837A improves the performance and
reduces the cost of power supplies. It is with 8-pin
DIP and 6-pin SOT-26 package.
Ordering and Marking Information
GR8837A
Package Code
J: DIP-8
C: SOT-26
RoHS Code
G: Green (Halogen Free) Device
L: PB Free Device
DIP-8
SOT-26
GR8837A
X X XXX
Code 1
Code 2
Serial No.
Code 1
37A X X
XXX
Code 2
Serial No.
Code 1 8 9 A B
GH
IJ
Year 2008 2009 2010 2011
2016
●●●
Code 2 1 2 3 4
9
2017
A
2018 2019
BC
Month Jan. Feb. Mar. Apr.
Sep. Oct. Nov. Dec.
Grenergy OPTO Inc. reserves the right to make changes to improve reliability or manufacture ability without notice, and
advise customers to obtain the latest version of relevant information to verify before placing orders.
2011.03 Ver. D.Copyright Grenergy OPTO, Inc. www.grenergy-ic.com
1







GR8837A pdf, 数据表
Preliminary GR8837A
OVP (Over Voltage Protection) on VCC
To prevent power MOSFET from being damaged,
the GR8837A is implemented an OVP function on
VCC. When the VCC voltage is higher than the OVP
threshold voltage, the output gate driver circuit will
be shut down immediately to stop the switching of
power MOSFET. The VCC pin OVP function is a
latch off type protection. If the OVP condition
happens, the pulses will be stopped and never
recovery unless the VCC pin voltage is down to
reset level. The GR8837A is working in a latch off
mode as shown in Fig. 11.
VCC
OVP
UVLO on
Holding
Reset
OUT
OVP Tripped
De-latch
t
voltage will down to UVLO off and the IC will re-start
again. In the GR8837A, before the VCC is down to
UVLO off, it will force the OUT pin outputs the
specified duty to pull the VCC higher than UVLO off.
The operation is shown in Fig.12.
VCC
VCC mode(off)
VCC mode(on)
UVLO(off)
LOAD
Full load
VCC mode
Burst mode
OUT
Switching
t
t
t
Switching
Non- Switching
Switching
t
Fig. 11
Gate Clamp/Soft Driving
Driver is clamped to 13V by an internal clamping
circuit. Those damages usually come from
undesired over-voltage gate signals. Under the
conditions listed below, the gate output will turn off
immediately to protect the power circuit. The
GR8837A also has soft driving function to minimize
EMI.
Fig. 12
The VCC mode function is used to prevent the
output re-start again when load changes. So never
let the system operate on the VCC mode at no load.
The system should operate on burst mode,
otherwise the input power maybe become larger.
RTL Pin Latch Off Mode
VDD
VH_TH
Latch off mode
3.5V
VCC Mode Operation
In order to avoid the output voltage shut down by
load changing from full to no load, the GR8837A is
built-in the VCC mode function. When the load from
RTL
pin
VL_TH
Normal Operation
Latch off mode
1V
full changes to no load, the output voltage will
overshoot and pull low the COMP pin by feedback
loop. Thus the duty will disappear and no power
delivers to the secondary. If there is without any
mechanism to prevent this situation, the VCC pin
Fig. 13
The typical application for RTL pin is shown in Fig.
13. The Zener diode is setting as external OVP
2011.03 Ver. D.Copyright Grenergy OPTO, Inc. www.grenergy-ic.com
8














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