pwm controller for programmable power converter …...2017/03/29 · external over-temperature...

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


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



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



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



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




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




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



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



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



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



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



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



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



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



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

pwm controller for programmable power converter …...2017/03/29 · external over-temperature...

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