Fairchild SG6905SZ, SG6905SZ Schematic

Product Specification

Green mode PFC/Flyback-PWM Controller SG6905

FEATURES

 Interleaved PFC/PWM switching  Green mode PWM operation  Low start-up and operating current  Innovative switching charge multiplier-divider  Multi-vector control for improved PFC output

transient response

 Average-current-mode control for PFC  PFC over-voltage and under-voltage protections  PFC remote on/off Control  PFC and PWM feedback open-loop protection  Cycle-by-cycle current limiting for PFC/PWM  Slope compensation for PWM  Constant power limit for PWM  Power-on sequence control  Brownout protection  Over temperature protection

achieve versatile protections. It is available in a 20-pin SOP package.

The patented interleave-switching feature synchronizes the PFC and PWM stages and reduces switching noise.

For PFC stage, the proprietary multi-vector control scheme provides a fast transient response in a low-bandwidth PFC loop, in which the overshoot and undershoot of the PFC voltage are clamped. If the feedback loop is broken, the SG6905 will shut off PFC to prevent extra-high voltage on output.

For the flyback PWM, the synchronized slope compensation ensures the stability of the current loop under continuous-conduction-mode operation. Built-in line-voltage compensation maintains constant output-power limit. Hiccup operation during output overloading is also guaranteed.

APPLICATI O NS

 Switching Power Suppliers with Active PFC  High-Power Adaptors

DESCRIPTI O N

The highly integrated SG6905 is specially designed for power supplies with boost PFC and flyback PWM. It requires very few external components to

TYPICAL APPLICATION

During start-up, the RDY pin will be pulled low until the PFC output voltage reaches to the setting level. This signal can be used to control the second power stage for proper power on sequence.

SG6905 provides complete protection functions such as brownout protection and RI pin open/short.

Product Specification

Green mode PFC/Flyback-PWM Controller SG6905

MARKING DIAG RAMS PIN CONFIGURATION

T: S = SOP P : Z =Lead Free

SG6905TP

XXXXXXXXYWWV

Null=regular package

XXXXXXXX: Wafer Lot Y: Year; WW: Week

V: Assembly Location

ORDERING INFORMATION

Part Number Pb-Free Package

SG6905SZ

20-pin SOP

Product Specification

Green mode PFC/Flyback-PWM Controller SG6905

PIN DESCRIPTIONS

Name Pin No. Type Function

VRMS 1

RI 2 Oscillator Setting

OTP 3

IEA 4

IPFC 5

IMP 6

ISENSE 7

FBPWM 8

IPWM 9 PWM Current Sense

AGND 10 Ground Signal Ground

SS 11 PWM Soft Start

OPWM 12 PWM Gate Drive

GND 13 Ground Power Ground

OPFC 14 PFC Gate Drive

VDD 15 Supply The power supply pin.

RDY 16 Ready signal output

PFC_ON 17 Remote On/Off The PFC stage will disabled whenever the voltage at this pin is exceed 2.45V.

FBPFC 18

VEA 19

IAC 20 Input AC Current

Line-Voltage

Detection

Over Temperature Protection

Output for PFC

Current Amplifier

Inverting Input for

PFC Current

Amplifier

Non-inverting Input

for PFC Current

Amplifier

Peak Current Limit

Setting for PFC

PWM Feedback

Input

Voltage Feedback

Input for PFC

Error-Amp Output for

PFC voltage

feedback loop

Line voltage detection. The pin is used for PFC multiplier, brownout protection .For

brownout protection; the controller will be disabled after a delay time when the VRMS

voltage drops below a threshold voltage.

Reference setting. One resistor connected between RI and ground determines the

switching frequency. The switching frequency is equal to [1560 / RI] kHz, where RI is in

kΩ. For example, if RI is equal to 24kΩ, then the switching frequency will be 65 kHz.

This pin supplies an over temperature protection signal. A constant current is output from this pin. An external NTC thermistor must be connected from this pin to ground. The impedance of the NTC thermistor decreases whenever the temperature increases. Once the voltage of the OTP pin drops below the OTP threshold, the SG6905 will be disabled.

This is the output of the PFC current amplifier. The signal from this pin will be compared

with an internal saw-tooth and hence determine the pulse width for PFC gate drive.

The inverting input of the PFC current amplifier. Proper external compensation circuits will

result in excellent input power factor via average-current-mode control.

The non-inverting input of the PFC current amplifier and also the output of multiplier.

Proper external compensation circuits will result in excellent input power factor via

average- current- mode control.

The peak-current setting for PFC.

The control input for voltage-loop feedback of PWM stage. It is internally pulled high

through a 6.5kΩ resistance. Usually an external opto-coupler from secondary feedback

circuit is connected to this pin.

The current-sense input for the Flyback PWM. Via a current sense resistor, this pin

provides the control input for peak-current-mode control and cycle-by-cycle current

limiting.

During startup, the SS pin will charge an external capacitor with a 50µA (RI=24kΩ) constant current source. The voltage on FBPWM will be clamped by SS during startup. In the event of a protection condition occurring and/or PWM being disabled, the SS pin will be quickly discharged.

The totem-pole output drive for the Flyback PWM MOSFET. This pin is internally

clamped under 17V to protect the MOSFET

The totem-pole output drive for the PFC MOSFET. This pin is internally clamped under

17V to protect the MOSFET

This pin outputs a ready signal to control the power on sequence. Once the SG6905 is

turned on and the FBPFC(PFC Feedback input)voltage is higher than 2.7V, will lock this

pin to high impedance. Disable the SG6905 Will reset this pin to the low.

The feedback input for PFC voltage loop. The inverting input of PFC error amp. This pin is

connected to the PFC output through a divider network.

The error-amp output for PFC voltage feedback loop. A compensation network (usually a

capacitor) is connected between this pin and ground. A large capacitor value will result in

a narrow bandwidth and hence improve the power factor.

Before start-up, this input is used to provide startup current for VDD. For normal

operation, this input is used to provide current reference for the multiplier.

.

Product Specification

Green mode PFC/Flyback-PWM Controller SG6905

BLOCK DIAG RAM

Product Specification

Green mode PFC/Flyback-PWM Controller SG6905

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

V

DC Supply Voltage* 25 V

VDD

IAC Input AC Current 2 mA

V

OPWM, OPFC, IAC -0.3 to +25 V

High

V

Others -0.3 to +7 V

Low

PD Power Dissipation At TA < 50°C 0.8 W

TJ Operating Junction Temperature -40 to +125 °C

T

Storage Temperature Range -55 to +150 °C

STG

R

Thermal resistance (Junction to Case) 23.64 °C/W

θ

j-C

TL Lead Temperature (Wave soldering or IR, 10 seconds) 260 °C

V

ESD capability, HBM model 4.5 KV

ESD,HBM

V

ESD capability, Machine model 250 V

ESD,MM

*All voltage values, except differential voltages, are given with respect to GND pin. *Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device.

RECOMMENDED OPERATING CONDITIONS

Symbol Parameter Value Unit

TA Operating Ambient Temperature* -20 to +85 °C

*For proper operation

ELECTRICAL CHARACTERISTICS (VDD=15V, TA=25°C UNLESS NOTED) VDD section

Symbol Parameter Test Conditions Min. Typ. Max. Unit

V

Continuously Operating Voltage 20 V

DD-OP

I

Start-up Current V

DD-ST

I

Operating Current VDD= 15V; RI= 24KΩ

DD-OP

V

Start Threshold Voltage 15 16 17 V

DD-ON

V

Min. Operating Voltage 9 10 11 V

DD-OFF

V

VDD OVP Threshold 23.5 24.5 25.5 V

DD-OVP

t

D-VDDOVP

V

DD-TH-G

Debounce Time of VDD OVP RI= 24KΩ 8 25 µs

VDD Low-Threshold Voltage to Exit

Green-OFF Mode

-0.16V 10 25 µA

DD-ON

6 10 mA

OPFC, OPWM open

V

DD-OFF

+0.9

V

DD-OFF

+1.5

V

DD-OFF

+2.1

V

Product Specification

Green mode PFC/Flyback-PWM Controller SG6905

VRMS for UVP

Symbol Parameter Test Conditions Min. Typ. Max. Unit

V

RMS-UVP-1

V

RMS-UVP-2

t

D-PWM

t

UVP

RMS AC Voltage Under Voltage Protection

Threshold (with T

UVP

delay)

Recovery level on VRMS

When UVP occurs, the interval from OPFC off

to OPWM off

Under Voltage Protection Delay Time

(No delay for startup)

0.75 0.8 0.85 V

RI= 24KΩ

V

RMS-UVP-

+0.17

1

t

UVP-Min

+9

V

RMS-UVP-

+0.19

1

V

RMS-UVP-

+0.21

1

t

UVP-Min

+14

V

ms

RI= 24KΩ 150 195 240 ms

PFC stage Voltage Error Amplifier

Symbol Parameter Test Conditions Min. Typ. Max. Unit

V

Reference Voltage 2.95 3 3.05 V

REF

Av Open-loop Gain 60 dB

Zo Output Impedance 110 KΩ

OVP



t

V

G

V

G

I

UVP

t

PFC Over-Voltage-Protection on FBPFC 3.2 3.25 3.3 V

FBPFC

OVP

PFC Feedback Voltage Protection Hysteresis 60 90 120 mV

PFC

Debounce Time of PFC OVP RI= 24KΩ 40 70 120 µs

OVP-PFC

Clamp-High Feedback Voltage 3.1 3.15 3.2 V

FBPFC-H

Clamp-High Gain 0.5 µA/mV

FBPFC-H

Clamp-Low Feedback Voltage 2.75 2.85 2.9 V

FBPFC-L

Clamp-Low Gain 6.5 mA/mV

FBPFC-L

Maximum Source Current 1.5 2 mA

FBPFC-L

Maximum Sink Current 70 110 µA

FBPFC-H

PFC Feedback Under Voltage Protection 0.35 0.4 0.45 V

FBPFC

Debounce Time of PFC UVP RI= 24KΩ 40 70 120 µs

UVP-PFC

Current Error Amplifier

Symbol Parameter Test Conditions Min. Typ. Max. Unit

V

Input Offset Voltage ((-) > (+)) 8 mV

OFFSET

AI Open-loop Gain 60 dB

BW Unit Gain Bandwidth 1.5 MHz

CMRR Common-mode Rejection Ratio VCM= 0~1.5V 70 dB

V

Output High Voltage 3.2 V

OUT-HIGH

V

Output Low Voltage 0.2 V

OUT-LOW

I

, I

Reference Current Source RI= 24 KΩ (IMR=20+IRI*0.8) 50 70 µA

MR1

MR2

IL Maximum Source Current 3 mA

IH Maximum Sink Current 0.25 mA

Product Specification

Green mode PFC/Flyback-PWM Controller SG6905

Peak Current Limit

Symbol Parameter Test Conditions Min. Typ. Max. Unit

IP Constant Current Output RI= 24KΩ 90 100 110 µA

VPK

t

PD-PFC

t

LEB-PFC

Peak Current Limit Threshold Voltage

Cycle-by-Cycle Limit (V

SENSE

< VPK)

Propagation Delay 200 ns

Leading Edge Blanking Time 70 120 170 ns

VRMS= 1.05V 0.15 0.2 0.25 V

VRMS= 3V 0.35 0.4 0.45 V

Multiplier

Symbol Parameter Test Conditions Min. Typ. Max. Unit

I

Input AC Current Multiplier Linear Range 0 360 µA

AC

I

Maximum Multiplier Current Output; RI= 24KΩ 250 µA

MO–max

I

MO-1

I

MO–2

V

Voltage of IMP Open 3.4 3.9 4.4 V

IMP

Multiplier Current Output

(low-line, high-power)

Multiplier Current Output

(high-line, high-power)

= 1.05V; IAC= 90µA;

V

RMS

VEA= 7.5V;RI= 24 KΩ

V

= 3V; IAC= 264µA;

RMS

V

= 7.5V;RI= 24 KΩ

EA

200 250 280 µA

65 85 µA

PFC Oscillator

Symbol Parameter Test Conditions Min. Typ. Max. Unit

F

PFC Frequency RI= 24KΩ 62 65 68 KHz

OSC

FDV Frequency Variation versus VDD Deviation VDD= 11 to 20V 2 %

FDT Frequency Variation versus Temp. Deviation TA= -20 to 85°C 2 %

PFC Output Driver

Symbol Parameter Test Conditions Min. Typ. Max. Unit

VZ Output Voltage Maximum (Clamp) VDD= 20V 16 18 V

V

Output Voltage Low VDD= 15V; IO= 100mA 1.5 V

OL-PFC

t

The interval of OPFC lags behind OPWM at

PFC

startup

V

Output Voltage High VDD= 13V; IO= 100mA 8 V

OH-PFC

t

Rising Time VDD= 15V; CL= 5nF;

R-PFC

t

Falling Time VDD= 15V;CL= 5nF;

F-PFC

DCY

Maximum Duty Cycle 93 98 %

MAX

8 11 13.5 ms

40 70 120 ns

O/P= 2V to 9V

40 60 110 ns

O/P= 9V to 2V

PFC On/Off

Symbol Parameter Test Conditions Min. Typ. Max. Unit

I

Constant Current Output for PFC_ON pin RI= 24KΩ 44 50 56 µA

ON/OFF

V

Turn-off Threshold Voltage 2 2.45 2.9 V

OFF

t

Debounce Time of PFC_On/Off RI= 24KΩ 40 70 120 µs

PFC_ON

Fairchild SG6905SZ, SG6905SZ Schematic [ru]