pwm controller for programmable power converter …...2017/03/29 · external over-temperature...
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Preliminary RT7786
Copyright © 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
DS7786-P01 February 2015 www.richtek.com 1
PWM Controller for Programmable Power Converter (USBPD)
General Description RT7786 series are specifically designed to work with
controller, such as RT7207, to provide a total solution for
USB PD or a programmable power adaptor. The system
could achieve high efficiency, safety and less than
30mW in 5V standby condition.
To cope with issues associated with a wide output
voltage, RT7786 has many new innovations. Through
the detection of DMAG pin, RT7786 could detect the
output voltage to adjust its loop gain to ensure system
stability, to adjust its OVP level to protect external
devices, and to adjust its current limit to meet Limited
Power Source (LPS) regulation.
RT7786 is also equipped with the complete protection
features, including Brown in/out, VDD OVP, VOUT UVP,
Secondary Rectifier Short circuit Protection (SRSP),
External Over-Temperature Protection (OTP) and Internal
OTP. To keep constant output power across universal
input range, user could use a resistor connected to CS
pin to get the best line compensation result. In case that
the secondary IC, RT7207, or shunt regulator fails,
RT7786 could detect the failure and do protections.
Together with RT7207, they could realize a highly safe
and robust design against versatile and unknown
connection to all different devices, cables, plugs and
receptacles.
Features
Optimized for Adaptive Output Power
Adaptive VOUT OVP
Adaptive OCP
Adaptive Loop Stability Control
High Efficiency
Green Mode operation in light load and no load
Sounded Protections
Brown in/out, VDD OVP, VOUT UVP, External OTP,
Internal OTP, Adaptive OVP, Adaptive OCP, SRSP,
Adjustable Line Compensation, Feedback Open
Loop Protection
Others
Power Saving < 30mW in 5V standby mode
Driver Capability : 200mA/300mA
SmartJitterTM Technology
Applications USB PD and Programmable Power Adaptor
Simplified Application Circuit
VOUT
GND
OPTOCOMP
GND
VDD
GATE
CS/OTP
DMAG
HV
CC1
CC2
CS- CS+VDD V2
BLDOPTO IFB VFB CC1 CC2
AGND
PGND
RT7786
RT7207D
USBP
AC Mains
++ +
V5 VCP V9
Preliminary RT7786
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www.richtek.com DS7786-P01 February 2015 2
Ordering Information
RT7786
Package Type
S : SOP-8
Lead Plating System
G : Green (Halogen Free and Pb Free)
RT7786 Version (Refer to Version Table)
B
Note :
Richtek products are :
RoHS compliant and compatible with the current
requirements of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
Marking Information For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
Pin Configurations (TOP VIEW)
DMAG
COMP
CS
GND
HV
NC
GATE
VDD
2
3
4 5
6
7
8
SOP-8
RT7786 Version Table
Version RT7786GD RT7786LD RT7786LE
VDD OVP Auto Recovery Latch Latch
Adaptive OVP Auto Recovery Latch X
Threshold Voltage of Output OVP 3.60V 3.60V 1.75V
Output OVP Auto Recovery Latch Latch
Output UVP Auto Recovery Auto Recovery Auto Recovery
OCP Auto Recovery Auto Recovery Auto Recovery
De-Bounce Time of OCP 48ms 48ms 48ms
SRSP Auto Recovery Auto Recovery Auto Recovery
External OTP Auto Recovery Latch Latch
RT7786 Preliminary
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DS7786-P01 February 2015 www.richtek.com 3
Functional Pin Description
Pin No. Pin Name Pin Function
1 DMAG Transformer Detection Input. The Input and Output Voltage Detection from the
Transformer Winding.
2 COMP Feedback Voltage Input. Connect an opto-coupler to close the control loop and
achieve output voltage regulation.
3 CS Current Sense Input. The current sense resistor between this pin and GND is used
for current limit setting.
4 GND Ground of the Controller.
5 VDD Supply Voltage of the Controller. The controller will be enabled when VDD exceeds
VTH_ON and disabled when VDD decreases lower than VTH_OFF.
6 GATE Gate Driver Output
7 NC No Internal Connection
8 HV High Voltage Terminal for Start-up.
Function Block Diagram
VDD
VOVP
HV
VTH_ON / VTH_OFF
Internal Bias &
Shutdown Logic
Burst Switching Green
Mode
Slope
Comp.
LEB
GATE
COMP
CS
DMAGVIN/VOUT
Detection
Internal OTP
VDD OVP
+-
x3R
S
Q
+
-
GND
COMP Open
Sensing
-
PWM
Comparator
UVLO
AC Voltage
DetectionBrown-in/out
Current Limit
Soft Driver
COMP
VDD
VBURL
VBURH
+
-
IDMAG_UCP
+
-
+
-
VTH_OVP
VTH_UVP
+
-VTH_OTP
+
-VTH_SRSP
Oscillator
TON_MAX
VCOMP_OP
+
-
Preliminary RT7786
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Operation
RT7786 series are specifically designed to work with
the USB PD controller or programmable power adapter
controller, to provide a total solution. For the wide
output voltage application, RT7786 features many new
innovations, including adaptive VOUT OVP, adaptive
OCP and adaptive loop stability control.
HV Pin
RT7786 provide a 700V high voltage pin to implement
the brown-in/out and fast start-up functions. Therefore,
the components and power loss of external
brown-in/out and start-up circuits can be reduced.
Multi-Mode PWM
The RT7786 is a multi-mode PWM controller which
could operate in Constant Current Mode (CCM).
Together with its green mode operation during light
load, RT7786 helps to improve the overall efficiency.
Gate Driver
A totem pole gate driver is designed to meet both EMI
and efficiency requirements in low power applications.
An internal pull-low circuit is activated for a low VDD to
prevent external MOSFET from accidentally turning on
during UVLO.
Adaptive Loop Stability Control
The system loop gain is different for wide range VOUT
range application. RT7786 features the proprietary
adaptively loop stability control and it would adjust loop
gain automatically to ensure the system stability for
different VOUT operation.
Adaptive VOUT Over-Voltage Protection (Except
RT7786XE)
For wide VOUT range application, RT7786 provides the
proprietary adaptive VOUT over voltage protection. The
threshold of adaptive VOUT OVP could be automatically
adjusted according to output voltage level. It could
provide the complete VOUT OVP when the fault occurs.
Adaptive Over Current Protection
For Example, a power designed for 20V/3A could
possibly output 12A when the VO is decreased to 5V,
given the output power is constant. This will violate the
rule of LPS and cause damage to the connected
devices if the secondary USB PD Controller RT7207
fails. Therefore, RT7786 could automatically adjust
down the current limit and its maximum current output if
it detects a lower VO output. It also provides the
cycle-by-cycle current limit and the controlled enters
protection mode after deglitch delay.
Secondary Rectifier Short Protection (SRSP)
In case that a secondary rectifier is short-circuit, it will
result in high current spike because of saturation of
main transformer. Before the OLP triggers, the
transformer current could possibly goes too high to
damage the power supply. RT7786 could detect this
abnormal condition and shut down the PWM within few
cycles.
RT7786 Preliminary
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Absolute Maximum Ratings (Note 1) HV to GND ----------------------------------------------------------------------------------------------------------0.3V to 700V(DC)
Supply Input Voltage, VDD to GND ---------------------------------------------------------------------------0.3V to 30V
GATE to GND ------------------------------------------------------------------------------------------------------0.3V to 16.5V
DMAG, COMP, CS to GND -------------------------------------------------------------------------------------0.3V to 6.5V
Power Dissipation, PD@ TA= 25C
SOP-8 ----------------------------------------------------------------------------------------------------------------0.36W
Package Thermal Resistance(Note 2)
SOP-8, θJA ----------------------------------------------------------------------------------------------------------276.5C/W
Junction Temperature --------------------------------------------------------------------------------------------150C
Lead Temperature (Soldering, 10 sec.) ----------------------------------------------------------------------260C
Storage Temperature Range -----------------------------------------------------------------------------------65C to 150C
ESD Susceptibility(Note 3)
HBM(Human Body Model)
Except HV Pin ------------------------------------------------------------------------------------------------------2kV
HV to GND ----------------------------------------------------------------------------------------------------------1kV
MM(Machine Model) ----------------------------------------------------------------------------------------------250V
Recommended Operating Conditions (Note 4) Supply Input Voltage, HV --------------------------------------------------------------------------------------- 0V to 500V (DC)
Supply Input Voltage, VDD ------------------------------------------------------------------------------------- 10V to 36V
Junction Temperature Range ---------------------------------------------------------------------------------- 40C to 125C
Ambient Temperature Range ---------------------------------------------------------------------------------- 40C to 85C
Electrical Characteristics (VDD=15V, TA=25°C, unless otherwise specified)
Parameter Symbol Test Conditions Min Typ Max Unit
HVSection
HV Start-Up Current IJEFT_ST VDD < VTH_ON, VHV = 500V -- 2 -- mA
Off State Leakage Current IHV_LK VDD > VTH_ON, VHV = 500V -- -- 30 A
Brown-In Threshold VTH_BNI DC Input Voltage -- 107 -- V
Brown-Out Threshold VTH_BNO DC Input Voltage -- 92 -- V
De-Bounce Time of
Brown-Out TD_BNO fOSC = 85kHz -- 60 -- ms
VDD Section
VDD Over-Voltage Protection
Threshold VOVP -- 27 -- V
On Threshold Voltage VTH_ON 16.5 17.5 18.5 V
Off Threshold Voltage VTH_OFF 6.5 7.0 7.5 V
VDD Holdup Mode Entry Point VDD_ET VCOMP < 0.95V 7.5 8.0 8.5 V
Preliminary RT7786
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Parameter Symbol Test Conditions Min Typ Max Unit
VDD Holdup Mode Ending
Point VDD_ED VCOMP<0.95V --
VDD_ET
+0.5 -- V
VDD Latched Voltage for
Protection VDD_LH Enter Protection Mode -- 8.0 -- V
VDD Latched Current for
Protection IDD_LH Enter Protection Mode -- 60 -- A
Operating Current IDD_OP Gate pin open, Comp pin open -- 550 -- A
Oscillator Section
Normal PWM Frequency fOSC VCOMP> VGM_ET -- 85 -- kHz
Maximum ON Time TON_MAX VCOMP = VCOMP_OP, fOSC = 65kHz -- 8.8 -- s
Minimum Green Mode
Frequency fGM_MIN VCOMP< VGM_ED -- 25 -- kHz
PWM Frequency Jittering
Range f -- ±6 -- %
PWM Frequency Jittering
Period TJIT fOSC = 85kHz -- 12 -- ms
Frequency Variation Versus
VDD Deviation fDV VDD = 8V to 35V -- -- 2 %
Frequency Variation Versus
Temperature Deviation fDT TA = 30C to 105C -- -- 5 %
COMP Input Section
Open Loop Voltage VCOMP_OP Comp pin open -- 2.90 -- V
COMP Short Circuit Current IZERO VCOMP = 0V -- 145 -- A
De-Bounce Time of COMP
Open-loop Protection TCOMP_OP -- 48 -- ms
Green Mode Entry Voltage VGM_ET VDMAG > 2.7V -- 1.75 -- V
Green Mode Ending Voltage VGM_ED VDMAG > 2.7V -- 1.55 -- V
Current Sense Section
Maximum Current Limit VCS_MAX VDMAG > 3V 0.375 0.400 0.425 V
De-Bounce Time of
Over-Current Protection TOCP -- 48 -- ms
Leading Edge Blanking Time TLEB 350 450 550 ns
Threshold Voltage of
Secondary Rectifier Short
Protection
VTH_SRSP (Note 5) -- 1.2 -- V
Threshold Voltage of External
Over-Temperature Protection VTH_OTP VDMAG > 3V -- 0.8 -- V
De-bounce Time of External
Over-Temperature Protection TD_OTP fOSC = 85kHz -- 48 -- ms
Cooling Time for Auto
Recovery Protection TCOOL 2.4 s
RT7786 Preliminary
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DS7786-P01 February 2015 www.richtek.com 7
Parameter Symbol Test Conditions Min Typ Max Unit
GATE Section
Rising Time TR CL = 1nF -- 250 -- ns
Falling Time TF CL = 1nF -- 30 -- ns
Gate Output Clamping
Voltage VCLAMP VDD = 23V -- 12 -- V
DMAG Section
Threshold Voltage of Output
Over-Voltage Protection VTH_OVP
RT7786XD 3.55 3.60 3.65 V
RT7786XE 1.70 1.75 1.80
Threshold Voltage of Output
Under-Voltage Protection VTH_UVP -- 0.45 -- V
De-bounce time of Output
Under-Voltage Protection TD_UVP fOSC = 85kHz -- 12 -- ms
Blanking Time of DMAG Pin TBK VCS_PK = 0.4V -- 2.3 -- s
Maximum Sourcing Current of
DMAG IDMAG_MAX 1000 -- -- A
Threshold Current of DMAG
Under-Current Protection IDMAG_UCP -- 50 -- A
Internal Over-Temperature Protection (OTP) Section
OTP Before Turn On TOTP_INTH Built-in OTP (Note 5) -- 130 -- C
OTP After Turn On TOTP_STTH Built-in OTP (Note 5) -- 140 -- C Note1. Stresses beyond those listed ”Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and functional operation of the device at these or any other condition beyond those indicated in the
operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may affect
device reliability.
Note 2. JA is measured in natural convection (still air) at TA = 25°C with the component mounted on a low effective thermal
conductivity test board of JEDEC 51-3 thermal measurement standard.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Note 5. Guaranteed by design.
Preliminary RT7786
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Typical Application Circuit VOUT
GND
OPTOCOMP
GND
VDD
GATE
CS
DMAG
HV
CC1
CC2
CS- CS+VDD V2
BLDOPTO IFB VFB CC1 CC2
AGND
PGND
RT7786
RT7207D
USBP
AC Mains
+
+ +
V5 VCP V9
Option
(Option)1 6
5
3
4
2
8
Option
RT7786 Preliminary
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DS7786-P01 February 2015 www.richtek.com 9
Application Information
RT7786 is a multi-mode PWM flyback controller. As
load decreases, the controller enters green mode, burst
mode, and VDD holdup mode. The automatic
multi-mode operation optimizes the product
performance under different load conditions.
Start-up
The RT7786 features a HV pin to provide fast start-up.
700V start-up device is integrated in the controller to
further minimize power consumption and enhance
performance. The start-up device will be turned on
during start-up and be turned off during normal
operation so as to shorten start-up time and to
eliminate power loss in this path after start-up.
As shown in Figure 1, the resistor RHV connected in
series with HV pin is recommended in the range from
2k to 6.6k (tolerance<±5%). A voltage-divider
(resistors) is built-in for the input voltage detection. The
RHV with value higher than 6.6k could possibly cause
inaccuracy of the brown-in and brown-out threshold.
COMP
GND
VDD
GATE
CS
AC Mains
(90V to 265V)
HV
OPTO
+RHV
+
Figure 1. Start-up Circuit
Brown-In and Brown-Out
The RT7786 features internal precise brown-in and
brown-out detections. An AC voltage detection circuit is
built in the controller so that the brown-in and
brown-out can be implemented without extra
components. The brown-out offers precise brown-out
detection without AC ripple effect at heavy or light load.
VDD Holdup Mode
The VDD holdup mode is designed to prevent VDD
from decreasing to the turn-off threshold voltage,
VTH_OFF, under light load or load transient. Comparing
with burst mode, the VDD holdup mode brings higher
switching. Hence, it is recommended that the system
should be designed to not to operate at this mode
during light load or no load conditions.
DMAG pin Resistor
When the MOSFET turns on, a clamping circuit of
DMAG pin clamps the DMAG voltage at 0.1V. When
the MOSFET turns off, the DMAG pin detects the
output voltage according to the ratio of auxiliary and
secondary turns, and the voltage divider (RDMAG1 &
RDAMG2), as shown in Figure 2.The voltage divider can
be calculated by the following formula :
3 ADMAG2
P
N750 10 R ( )
N
DMAG2DMAG1
OUT F A
TH_OVP S
RR ( )
(V 120% V ) N1
V N
VOUT
DMAG VDMAG
VIN
RDMAG2
RDMAG1
NP NS
NA
+ VF -
VAUXVDO
GATE
CS
RCS
Q1
Figure 2. DMAG Pin Resistor
Adaptive Blanking Time
The output voltage signal can be detected indirectly via
the transformer and the voltage divider (RDMAG1 &
RDAMG2). When the MOSFET turns off, the leakage
inductance of the transformer and parasitic
capacitance (COSS) of MOSFET induce resonance
waveform on the DMAG pin, as shown in Figure 3. The
resonance waveform makes improper detection of
VDMAG, and it may cause the controller operate in
Preliminary RT7786
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www.richtek.com DS7786-P01 February 2015 10
unstable condition. As load increases, the resonance
time also increases. The RT7786 provides adaptive
blanking time to prevent VDMAG from improper
detection. The blanking time (TBK) varies with the CS
peak voltage (VCS_PK), and the blanking time can be
calculated by the following formula:
BK CS_PK T 1.75μs 1.375(μs/V) V (Typ.)
It is also recommended to add 10pF ~ 47pF bypass
capacitor to avoid noise false triggering on DMAG pin.
The bypass capacitor should be placed as close to
DMAG pin as possible.
TBK
VDMAG
VDMAG
0V
-VCS
VCS_PK
Figure 3. Resonance Waveform on DMAG Pin
External Over-Temperature Protection (Ext-OTP)
RT7786 has an adjustable external over-temperature
protection by using CS pin and the constant voltage
source of (VAUX_Clamp). A fast diode and the voltage
divider on CS pin for OTP are shown in Figure 4. The
voltage source is sensed by auxiliary voltage during
PWM off, and the voltage divider consists of NTC
Resistor (RNTC), setting resistors (RSET& RPDC), and
current sense resistor (RCS). When the temperature
rises, the resistance of NTC resistor becomes smaller.
When the Gate is off and the sampling voltage of the
voltage divider on CS pin exceeds the VTH_OTP level,
the controller will be shut down and cease switching
after de-bounce time TD_OTP. The controller will
resume operation if the OTP condition is released. The
design equation is :
ATH_OTP D F_OTP
S
PDC CS
NTC_OTP SET PDC CS
NV 20V V -V
N
R R
R R R R
where RNTC_OTP is the NTC resistance at
over-temperature.
Blanking Time
VAUX_Clamp
TS
TON
TBK
Sample
VOTP_TH
AO F F_OTP
S
N(V + V ) V
N
COMP
GND
VDD
GATE
CS
DMAG
HV
RT7786
AC Mains
+
+
VOUT
GND
NS
+ VF -+
VO
-
+
NP
+
VBulk
-
RSET
RPDC
RCS
NA
+VAUX
-
+VF_OTP
-
VAUX_Clamp
RNTC
Figure 4. Application Circuit of External Over-Temperature Protection
RT7786 Preliminary
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DS7786-P01 February 2015 www.richtek.com 11
Internal Over-Temperature Protection
RT7786 provides internal OTP function to prevent
permanent damage of IC. It is not recommended to
apply this function to accurate temperature control.
When the IC turns on, the controller detects surround
temperature before it starts switching. If the
temperature is higher than TOTP_INTH (Typ. 130C), it
will trigger internal OTP and stop output signal. If the
temperature is lower than TOTP_INTH, the controller
starts operation and the OTP threshold is automatically
set to TOTP_STTH (Typ. 140C), which means when the
controller starts switching, the OTP threshold is
TOTP_STTH.
When the controller triggers internal OTP, the controller
will be shut down and cease switching. At the same
time, VDD drops below VDD off threshold VTH_OFF, the
controller enters hiccup mode.
Resistors on GATE pin
As shown in Figure 5, RG is applied to alleviate the
ringing voltage of the gate drive loop in typical
application circuits. The resistance of the RG must be
considered carefully for system EMI and efficiency.
RT7786 has an internal parallel resistor RID inside Gate
pin to discharge the accumulated electron in the gate to
drain parasitic capacitance CGD so that a falsely trigger
of MOSFET could be prevented. An external parallel
resistor RED is still recommended to be added so that
this falsely MOSFET turn on could also be prevented
even if RT7786 is not placed or Gate pin is open.
AC Mains
(90V to 265V)
GND
GATE
CS
RG
RED
CGD
RID
Soft
Driver
RT7786 builds in a internal discharge-
resistor to avoid MOSFET falsely triggering
at any uncertain conditions.
Recommend to add the external discharge-
resistor to avoid MOSFET falsely triggering.
RID : Internal Discharge-Resistor
RED : External Discharge-Resistor
+
Figure 5. Resistors on Gate Pin
Feedback Resistor
In order to enhance light load efficiency, the loss of the
feedback resistor in parallel with the photo-coupler is
reduced, as shown in Figure 6. Due to small feedback
resistor current, the selection of shunt regulator
(Ex.TL-431) and its minimum regulation current must
be considered carefully to make sure it's able to
regulate under low cathode current. + + Vo+
Vo-
Feedback
Resistor
Figure 6. Feedback Resistor
Negative Voltage Spike to all Pins
Any negative voltage less than 0.3V should be
prevented in all condition for all of pins. An R-C filter
should be added outside of CS pin to prevent from
negative voltage damage caused by improper PCB
layout or inductive current sense resistor, as shown in
Figure7. Proper PCB layout and component selection
should be considered during circuit design.
COMP
GND
VDD
GATE
CS
AC Mains
(90V to 265V)
HV
OPTO
+
R-C Filter
+
Figure 7. R-C Filter on CS Pin
Preliminary RT7786
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Thermal Considerations
For continuous operation, do not exceed absolute
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and
difference between junction and ambient temperature.
The maximum power dissipation can be calculated by
the following formula :
PD(MAX) = (TJ(MAX) TA) / JA
where TJ(MAX) is the maximum junction temperature,
TA is the ambient temperature, and JAis the junction to
ambient thermal resistance.
For recommended operating condition specifications,
the maximum junction temperature is 125C. The
junction to ambient thermal resistance, JA, is layout
dependent. For SOP-8 package, the thermal resistance,
JA, is 276.5C/W on a standard JEDEC 51-3
single-layer thermal test board. The maximum power
dissipation at TA = 25C can be calculated by the
following formula :
PD(MAX) = (125C 25C) / (276.5C/W) = 0.36W for
SOP-8 package
The maximum power dissipation depends on the
operating ambient temperature for fixed TJ(MAX) and
thermal resistance, JA. The derating curve in Figure 8
allows the designer to see the effect of rising ambient
temperature on the maximum power dissipation.
Figure 8. Derating Curve of Maximum Power
Dissipation
Layout Consideration
A proper PCB layout could abate unknown noise
interference and EMI issue in a switching power supply
design. Therefore, following below layout guideline is
recommended.
The current path(1), starting from bulk capacitor,
transformer, MOSFET, RCS and back to bulk
capacitor, is a high frequency and high current loop.
Another high frequency and high current loop is
path(2) which is from GATE pin, MOSFET, RCS and
back to IC ground. These two paths should be kept
as short as possible to decrease noise coupling and
kept a space from other low voltage traces, such as
IC control circuit paths, especially.
The path(3), starting from auxiliary winding, resistor,
diode, and VDD capacitor to VDD pin, is also
recommended to be as short as possible.
Beside, place VDD capacitor as close as to the VDD
pin.
The path(4) from RCD snubber circuit to MOSFET
should also be kept short as it is also a loop with high
switching frequency.
The ground traces of bulk capacitor(a),MOSFET(b),
VDD capacitor(c), auxiliary winding(d) and IC control
circuit(e) should be separated to reduce noise,
output ripple and emission. Connect the ground
traces of auxiliary winding(d) and IC control circuit(e)
together at VDD capacitor ground(c). Then the
ground trace starts from VDD capacitor ground(c),
MOSFET ground(b) to bulk capacitor ground (a) in
turn. The area of bulk capacitor ground should be
large enough.
Place the bypass capacitor as close to the controller
as possible.
In order to reduce reflected trace inductance and
EMI, minimize the area of the loop connecting the
secondary winding, output diode and output filter
capacitor. In additional, apply sufficient copper area
at the anode and cathode terminal of the diode for
the heat-sink.
0.0
0.1
0.2
0.3
0.4
0.5
0 25 50 75 100 125
Ambient Temperature (°C)
Ma
xim
um
Po
we
r D
issip
atio
n (
W) 1 Signal-Layer PCB
RT7786 Preliminary
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DS7786-P01 February 2015 www.richtek.com 13
DMAG
COMP
GND
VDD
GATE
CS
RT7786
AC Mains
(90V to 265V)
HV
2
3
4
5
6
8
1
(1)
(2)
(4)
OPTO
+ +
+
IC
Ground (e)
Auxiliary
Ground (d)
Trace
Trace
Trace
MOSFET
Ground (b)
CBULK Ground (a)
(3)
(a)
(b)
(d)
(c)
(e)
VDD
Ground (c)
Trace
Figure 9. PCB Layout Guide
Preliminary RT7786
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www.richtek.com DS7786-P01 February 2015 14
Outline Dimension
Symbol Dimensions In Millimeters Dimensions In Inches
Min Max Min Max
A 4.801 5.004 0.189 0.197
B 3.810 3.988 0.150 0.157
C 1.346 1.753 0.053 0.069
D 0.330 0.508 0.013 0.020
F 1.194 1.346 0.047 0.053
H 0.170 0.254 0.007 0.010
I 0.050 0.254 0.002 0.010
J 5.791 6.200 0.228 0.244
M 0.400 1.270 0.016 0.050
8-Lead SOP Plastic Package
Richtek Technology Corporation 14F, No. 8, Tai Yuen 1st Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789 Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries.
RT7786 Preliminary
Copyright © 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
DS7786-P01 February 2015 www.richtek.com 15
Datasheet Revision History
Version Date Item Description
P00 2015/1/8 First Edition
P01 2015/2/3
General Description
Applications
Simplified Application Circuit
RT7786 Version Table
Function Block Diagram
Operation
Electrical Characteristics
Typical Application Circuit
Application Information
Modify