Silan SD4870A, SD4870C, SD4870TR Schematic [ru]

CURRENT MODE PWM CONTROLLER

DESCRIPTION

SD4870 is a current mode PWM controller IC for high performance,

low standby power offline flyback converter application.

In no load or light load condition, the IC operates in Light Load

Mode to reduce switching loss and improve efficiency.

Large value startup resistor could be used in the startup circuit to

minimize the standby current because of low startup current.

SD4870 offers complete protection functions including cycle-by-

cycle over current protection, over load protection, V

over voltage and under voltage protection, etc.

Excellent EMI performance is achieved with frequency shuffling

technique and soft switching control at the totem pole gate driver

output.

DD voltage

SD4870_Datasheet

SOT-23-6L

SOP-8-225-1.27DIP-8-300-2.54

FEATURES

* Frequency shuffling to improve EMI performance

* Light Load Mode for minimum standby power

* External programmable switching frequency

* 3uA low startup current

* Internal LEB circuit

DD over voltage and under voltage protection

* V

* Gate output maximum voltage clamp

* Current limiting

* Over load protection

* SOT-23-6L/SOP8/DIP8 package

APPLICATIONS

* Battery Chargers

* Adapters

* Set-Top Box Power Supplies

ORDERING INFORMATION

Part No. Package Marking Material Packing

SD4870TR SOT-23-6L 4870 Pb free Tape & Reel

SD4870A DIP-8-300-2.54 SD4870A Pb free Tube

SD4870C SOP-8-225-1.27 SD4870C Pb free Tube

SD4870CTR SOP-8-225-1.27 SD4870C Pb free Tape & Reel

HANGZHOU SILAN MICROELECTRONICS CO.,LTD

Http://www.silan.com.cn Page 1 of 9

REV:1.3 2010.12.29

BLOCK DIAGRAM

SD4870_Datasheet

ABSOLUTE MAXIMUM RATINGS

Characteristics Symbol Rating Unit

VDD Voltage VVDD 25 V

FB Voltage VFB -0.3~6 V

SENSE Voltage VSENSE -0.3~6 V

RI Voltage VRI -0.3~6 V

Junction Temperature Tj -20~150 °C

Lead Temperature TL 260 °C

Storage Temperature Tstg -55~160 °C

HANGZHOU SILAN MICROELECTRONICS CO.,LTD

Http://www.silan.com.cn Page 2 of 9

REV:1.3 2010.12.29

SD4870_Datasheet

ELECTRICAL CHARACTERISTICS (Unless otherwise specified, Tamb=25°C)

Characteristics Symbol Test Condition

VDD

Startup Current IVDD_ST VDD=12 V,RI=100kΩ -- 3 20 μA

DD=16V, VFB =3V,

Operation Current IVDD

UVLO Threshold Voltage VUVLO 13.3 14.3 15.3 V

UVLO Hysteresis Voltage VUVLOH -- 6.3 -- V

VDD Clamp Voltage VVDD_CLP IVDD =10mA -- 21.5 -- V

Feedback

PWM Gain AVCS ΔVFB /ΔVSENSE -- 2 -- V/V

FB Open Loop Voltage

FB Short Circuit Current IFB_SHORT

FB OL Threshold Voltage VFB_OL -- 3.8 -- V

OL Debounce Time TD_OL 35 -- ms

FB Input Impedance ZFB_IN 4 6 -- kΩ

Maximum Duty Cycle DMAX

Current Sense

LEB Time TLEB RI=100kΩ -- 300 -- ns

SENSE Input Impedance ZSENSE_IN -- 85 -- kΩ

OC Control Delay TOC -- 75 -- ns

OC Detection Threshold VSENSE_OC 0.7 0.75 0.8 V

Switching Frequency

Ocsillation Frequency fS RI=100kΩ 60 65 70 kHz

Frequency Stability With

DD

V

RI External Resistance

Range

Light Load Mode

Frequency

Frequency Shuffling Range ΔfS_SHUF RI=100kΩ -3 -- 3 %

Gate Driver

Output Low Level VOL VDD=16V, IO=-20mA -- -- 0.8 V

Output High Level VOH VDD=16V, IO=20mA 10 -- -- V

Output Clamp Voltage

Level

Output Rising Time TR VDD=16V,CL=1nF -- 220 -- ns

Output Falling Time TF VDD=16V,CL=1nF -- 70 -- ns

B_OPEN

VF

S_VDD VDD=12~25V,RI=100kΩ -- 5 -- %

Δf

R

RI_RANGE

f

S_LLM

V

OH_CLAMP

V

I=100kΩ

R

FB short connected to

nd

grou

DD=16V, RI=100kΩ

V

FB =3V,VSENSE =0V

V

Min. Typ. Max.

-- 2 -- mA

4.5 4.8 5 V

0.8 1 1.2 mA

-- 75 -- %

50 100 150 kΩ

-- 22 -- kHz

-- 13 -- V

Unit

HANGZHOU SILAN MICROELECTRONICS CO.,LTD

Http://www.silan.com.cn Page 3 of 9

REV:1.3 2010.12.29