Fairchild SG5842A, SG5842JA service manual

December 2009

SG5842A/SG5842JA — Highly Integrated Green-Mode PWM Controller

Features

 Green-Mode PWM Controller  Low Startup Current: 14µA  Low Operating Current: 4mA  Programmable PWM Frequency with Hopping

(SG5842JA)

 Peak-Current-Mode Control  Cycle-by-Cycle Current Limiting  Synchronized Slope Compensation  Leading-Edge Blanking (LEB)  Constant Output Power Limit  Totem-Pole Output with Soft Driving  V

Over-Voltage Protection (OVP)

DD

 Programmable Over-Temperature Protection (OTP)  Internal Latch Circuit (OTP, OVP)  Internal Open-Loop Protection  V

Under-Voltage Lockout (UVLO)

DD

 GATE Output Maximum Voltage Clamp: 18V

Applications

General-purpose switch-mode power supplies and

flyback power converters, including:

 Notebook Power Adapters  Open-Frame SMPS

Description

The highly integrated SG5842A/JA series of PWM controllers provides several features to enhance the performance of flyback converters. To minimize standby power consumption, a proprietary green-mode function provides off-time modulation to continuously decrease the switching frequency at light-load conditions. To avoid acoustic-noise problems, the minimum PWM frequency set above 22KHz. This green-mode function enables the power supply to meet international power conservation requirements. To further reduce power consumption, SG5842A/JA is manufactured using the BiCMOS process. This allows a low startup current, around 14µA, and an operating current of only 4mA. As a result, a large startup resistance can be used.

The SG5842A/JA built-in synchronized slope compensation achieves stable peak-current-mode control. SG5842JA integrates a frequency-hopping function that helps reduce EMI emission of a power supply with minimum line filters.

SG5842A/JA provides many protection functions. In addition to cycle-by-cycle current limiting, the internal open-loop protection circuit ensures safety should an open-loop or output short-circuit failure occur. PWM output is disabled until V limit, then the controller starts again. As long as V exceeds about 24V, the internal OVP circuit is triggered. An external NTC thermistor can be applied for overtemperature protection.

SG5842A/JA is available in an 8-pin DIP or SOP package.

drops below the UVLO lower

DD

Ordering Information

SG5842A/SG5842JA — Highly Integrated Green-Mode PWM Controller

Operating

Part Number

Temperature

Range

SG5842JASZ -40°C to +105°C RoHS

SG5842JADZ -40°C to +105°C RoHS

SG5842JASY -40°C to +105°C Green

SG5842ASZ (Preliminary)

SG5842ASY (Preliminary)

For Fairchild’s definition of Eco Status, please vis i t: http://www.fairchildsemi.com/company/green/rohs_green.html.

-40°C to +105°C RoHS

-40°C to +105°C Green

Eco

Status

Package

8-Pin Small Outline Package (SOP)

8-Pin Dual Inline Package (DIP)

8-Pin Small Outline Package (SOP)

OTP

Latch

Yes Yes Yes

Yes Yes No

OVP

Latch

Application Diagram

Frequency

Hopping

Figure 1. Application Diagram

Block Diagram

SG5842A/SG5842JA — Highly Integrated Green-Mode PWM Controller

Marking Information

Marking for SG5842JASZ (pb-free) Marking for SG5842JADZ (pb-free) Marking for SG5842ASZ (pb-free) Marking for SG5842ADZ (pb-free)

Marking for SG5842JASY (green-compound) Marking for SG5842ASY (green-compound)

SG5842HATP

XXXXXXXXYWW V

Figure 2. Function Block Diagram

ZXYTT SG5842HA TPM

H: J = with Frequency Hopping

Null = without Frequency

Hopping

T: D = DIP, S = SOP P: Z = Lead Free

Null = Regular Package

XXXXXXXX: Wafer Lot Y: Year; WW: Week V: Assembly Location

F- Fairchild Logo

Z- Plant Code X- 1 Digit Year Code Y- 1 Digit week Code TT: 2 Digits Die Run Code T: Package Type (S=SOP, D=DIP) P: Y: Green Package M: Manufacture Flow Code

Figure 3. Top Mark

Pin Configuration

Figure 4. Pin Configuration

Pin Definitions

Pin # Name Description

1 GND Ground

The signal from the external compensation circuit is fed into this pin. The PWM duty cycle is

2 FB

3 VIN

4 RI

5 RT

6 SENSE

7 VDD Power supply. The internal protection circuit disables PWM output if VDD is over-voltage.

8 GATE The totem-pole output driver for the power MOSFET, which is internally clamped below 18V.

determined in response to the signal from this pin and the current-sense signal from Pin 6. If FB voltage exceeds the threshold, the internal protection circuit disables PWM output after a predetermined delay time.

For startup, this pin is pulled HIGH to the rectified line input via a resistor. Since the startup current requirement is very small, a large startup resistance can be used to minimize power loss.

A resistor connected from the RI pin to GND provides a constant current source. This determines the center PWM frequency. Increasing the resistance reduces PWM frequency. Using a 26KΩ resistor results in a 65KHz center PWM frequency.

For over-temperature protection. An external NTC thermistor is connected from this pin to the GND pin. The impedance of the NTC decreases at high temperatures. Once the voltage of the RT pin drops below a fixed limit, PWM output is latched off.

Current sense. The sensed voltage is used for peak-current-mode control and cycle-by-cycle current limiting.

SG5842A/SG5842JA — Highly Integrated Green-Mode PWM Controller

Absolute Maximum Ratings

Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only.

Symbol Parameter Min. Max. Unit

V

Supply Voltage

VDD

V

Input Terminal 30

VIN

VFB Input Voltage to FB Pin -0.3 7.0

V

Input Voltage to SENSE Pin -0.3 7.0

SENSE

VRT Input Voltage to RT Pin -0.3 7.0

VRI Input Voltage to RI Pin -0.3 7.0

PD Power Dissipation (TA < 50°C )

ΘJA

Thermal Resistance (Junction-to-Air)

TJ Operating Junction Temperature -40 +125

T

Storage Temperature Range -55 +150

STG

T

L

Lead Temperature (Wave Soldering or Infrared, 10 Seconds) +260

ESD Electrostatic Discharge Capability

Notes:

1. All voltage values, except differential voltage, are given with respect to GND pin.

2. Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device.

(1)

30

V

DIP 800

SOP 400

DIP 82.5

SOP 141

mW

°C/W

°C

Human Body Model, JESD22-A114

Charged Device Model, JESD22-C101

3

KV

1

Recommended Operating Conditions

The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended operating conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not recommend exceeding them or designing to Absolute Maximum Ratings.

Symbol Parameter Min. Max. Unit

TA Operating Ambient Temperature -20 +85 °C

Fairchild SG5842A, SG5842JA service manual

Specifications and Main Features

Frequently Asked Questions

User Manual