SC4820AISTR [SEMTECH]

Switching Controller, 1A, PDSO8, SO-8;


型号：	SC4820AISTR
厂家：	SEMTECH CORPORATION
描述：	Switching Controller, 1A, PDSO8, SO-8 开关光电二极管
文件：	总12页 (文件大小：636K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

SC4820

Push-Pull Controller

ꢀor Isolated Power Supplies

PRELIMINARY

POWER MANAGEMENT

ꢀeatures

Description

The SC4820 is a controller with maximum features for

its small SO-8 outline. It is optimized for cost critical

applications requiring minimum space.

u Current mode

u Cycle by Cycle current limit

u Direct drive for N-channel MOSꢀETs with non-

overlap protection

u Internal leading edge blanking

u Undervoltage lockout with user

programmable hysteresis

The controller is intended for converters used in push-

pull and bridge topologies, typically in point of use power

supplies with 18V to 75V supply rails, but can be readily

adapted for other input voltage ranges.

u Soft start

u Dead time control built in

u 1 Amp peak drive capability

u Precise thermal shutdown

u Trimmed switching frequency

The controller is a current mode device, with slope com-

pensation, and cycle by cycle current limit, which pro-

vides rapid transient response and prevents core satu-

ration. Use of low voltage, fully differential logic in the

control circuit, allows high frequency capability together

with optimum low noise performance.

Applications

The device is capable of driving power MOSꢀETs with up

to 1 Amp peak drive current, and is available in two

switching frequency options.

u Telecom and datacom power supplies

u Point of use power supplies

Typical Application Circuit

www.semtech.com

Revision 2, ꢀebruary 2001

SC4820

Push-Pull Controller

ꢀor Isolated Power Supplies

PRELIMINARY

POWER MANAGEMENT

Absolute Maximum Ratings

Parameter

Symbol

Maximum

Units

V_CC

Cload

Thermal Resistance Junction to Case

Thermal Resistance Junction to Ambient

Operating Temperature Range

Storage Temperature Range

Lead Temperature (Soldering) 10 seconds

°C/W

°C

θ_JC

θ_JA

165

T_A

-40 to 85

-60 to 150

300

T_STG

T_LEAD

°C

Electrical Characteristics

Unless specified: V_CC= 12V; T_A= 25^oC

Parameter

Conditions

MIN

TYP

MAX

UNITS

Supply Voltage Range

VCC Lockout Threshold

Supply Current

6.5

No gate pulses

Supply Current

F_OSC= 250 kHz, CL = 3nF

F_OSC= 500 kHz, CL = 3nF

Supply Current

Undervoltage Lockout

Lower Threshold

3.182

(-5%)

3.350

3.518

(+5%)

Hysteresis Current ⁽¹⁾

Soft Start

µA

Charge Voltage

3.1

3.25

kohm

Input Resistance

Discharge Voltage ⁽²⁾⁽³⁾

Peak Discharge Voltage ⁽²⁾⁽³⁾

SS / Drive Enable Threshold

Oscillator

I_SS(inj) = 100µA

I_SS(inj) = 3mA

100

0.5

200

0.6

2.25

2.55

2.75

Operating Frequency

(when trimmed to 250kHz)

(when trimmed to 500 kHz)

SC4820A, Tj = 25°C

SC4820B, Tj = 25°C

Internally Preset

237.5

(-5%)

475

250

500

262.5

(+5%)

525

kHz

(-5%)

(+5%)

Slope Compensation (Preset) ⁽⁵⁾

mVp-p

%/µA

Slope Compensation (External) ⁽⁴⁾

Current Sense

Modulation sensitivity

C_L= 3nF

±0.5

Propagation Delay to Gate

Current Limit

150

Threshold

0.8

1.6

1.05

1.9

1.4

2.2

Crowbar Threshold

www.semtech.com

2001 Semtech Corp.

SC4820

Push-Pull Controller

ꢀor Isolated Power Supplies

PRELIMINARY

POWER MANAGEMENT

Electrical Characteristics (Cont.)

Parameter

Feedback

Conditions

In linear range

MIN

TYP

5.0

MAX

UNITS

(5)

Input Quiescent Voltage

4.5

5.5

(5)

Input Resistance

100

Kohm

(5)

Gain (to comp. Input)

Drive

Gate "Low" Voltage

V_CC= open, 2µA into G1, G2

0.1

V_CC= 12V, no switching, 1mA into

G1, G2

Gate "High" Voltage

Peak Sink Current

Peak Source Current

Rise Time

V_CC- 1.2 V_CC- 1.0

0.7

C_L= 3nF

Fall Time

Leading Edge Blanking

(5)

Blank Time

Dead Time Control

Dead Time

F = 250kHz

F = 500kHz

350

250

Thermal Protection

High Threshold

Hysteresis

150

°C

Notes:

(1) When input voltage is ramped up, 43µA flows into UVLO pin until pin voltage reaches “HIGH” threshold.

(2) Clmax = 20nF @ 250kHz; Clmax = 15nF @ 500kHz.

(3) Specified current, lss (inj) flows into soft start pin, soft start voltage is “Low”.

(4) ±10µA injected or removed from soft start pin will change slope compensation to 30% and 20%, respec-

tively.

(5) Guaranteed by design.

www.semtech.com

2001 Semtech Corp.

SC4820

Push-Pull Controller

ꢀor Isolated Power Supplies

PRELIMINARY

POWER MANAGEMENT

Pin Configurations

Ordering Information

Device⁽¹⁾

Freq. kHz Device Temp. Range

(T_J)

(TOP VIEW)

SC4820AISTR

SC4820BISTR

SC4820EVB-A

SC4820EVB-B

250

-40 to 150°C

SO-8

500

SC4820A Evaluation Board

SC4820B Evaluation Board

Note: (1) Only available in tape and reel packaging. A

reel contains 2500 devices.

(8-Pin SOIC)

Pin Descriptions

Pin#

Pin Name

Description

VCC

Chip power supply voltage.

Gate drive of FET A.

UVL

Under voltage lockout. This pin acts as a 43µA current sink below UVLO upper threshold

when the UVLO sense voltage is swept upwards from zero volts. The hysteresis is

determined by this sink current and the source resistance of the UVLO sense voltage divider

resistors, as observed at the UVLO.

Feedback. This pin has a high source resistance in the linear region and below. Source

resistance reduces to 3 kohm above the linear region.

Current sense. The pin receives the current sense signal from the current transformer. The

current limit threshold is typically 1.05V. The Crowbar Threshold is at 1.9V typical. When the

Crowbar Threshold is reached the Gate Drives are turned off and latched "Low". The soft

start pin is also latched to approx. 1.0V. This condition stays unchanged until the soft start pin

is momentarily forced to GND, or the supply voltage is switched off.

Soft start/Enable. The input resistance to this pin is 60 kohm typical. The input resistance and

the external soft start capacitor determine the soft start delay. Soft start begins as the Drive

Enable threshold is passed. After the soft start cycle is completed, the soft start pin voltage is

3.1V. When up to ±10µA is injected into this pin, the internal ramp compensation changes

from its preset value which is 25% to approx. 30% or 20%, respectively. The soft start pin

can also be utilized as Enable/Disable pin. When the soft start pin voltage is held below the

Drive Enable threshold, the device will not generate switching waveforms. When the device is

latched in "Crowbar" condition, the soft start pin is set to 1V. The "Crowbar" condition can be

removed by momentarily shorting the soft start pin to GND.

Gate drive of FET B.

Ground.

GND

www.semtech.com

2001 Semtech Corp.

SC4820

Push-Pull Controller

ꢀor Isolated Power Supplies

PRELIMINARY

POWER MANAGEMENT

Block Diagram

www.semtech.com

2001 Semtech Corp.

SC4820

Push-Pull Controller

ꢀor Isolated Power Supplies

PRELIMINARY

POWER MANAGEMENT

Typical Applications

ISOLATED APPLICATION - 48V Input, 5V/10A Output. Using SC4820B

www.semtech.com

2001 Semtech Corp.

SC4820

Push-Pull Controller

ꢀor Isolated Power Supplies

PRELIMINARY

POWER MANAGEMENT

Typical Applications (Cont.)

Bill of Material for Isolated Application

Item

Qty Reference

Part Number/Value

Manufacturing

C1,C2

C3,C4

C6,C7

2.2n, 50V, 1206, Cer.

150p, 200V, ±5%, NPO, Cer.

1.0u, 100V, 1812, Cer.

150p, 1206, Cer.

Any

Any.

100p, 1206, Cer.

C11

1.0u, 1206, Cer.

C17 - C21

33u, 8V, SMD, Poly. Alum. Cap.

Panasonic

P/N: EEF-CDOK330R

C22,C23,C24

C33

0.33u, 1206, Cer.

33n, 1206, Cer.

Any

C35

4.7n, 1206, Cer.

Any

C36

82n, 1206, Cer.

Any

C37

0.47u, 1206, Cer.

Any

C47

0.1u, 1206, Cer.

Any

D1,D2

35V, 25A, TO-220AC, Schottky

250V, 100mA, SOT-23

30V, 200mA, Schottly

12V, 500mW, SOD-123

75V, 50mA, SOT-23

10V, 500mW, SOD-123

E-I Core - Inductor

Motorola P/N: MBR2535CTL

Motorola P/N: BAS21LT1

Any. MA729-(TX)

Any. MMSZ4699T1

Motorola P/N: BAS16LT1

Any. MMSZ4697T1

Magnetics. R-41805-E&I

Any

D4,D7, D9

D10

4-Layer FR-4 PCB, Inductor, 1.5µH

M1,M2

200V, 18A, 0.18 ohm, TO-220AB, MOSFET IR P/N: IRF640

100V, 1000mA, SOT-23, NPN Bipolar

2.2, 5%, 1206, 1/8W

Any. FMMT493TA

R1,R30

R2,R3

R5,R6

Any

5.1, 5%, 1206, 1/8W

56, 5%, 1206, 1/8W

www.semtech.com

2001 Semtech Corp.

SC4820

Push-Pull Controller

ꢀor Isolated Power Supplies

PRELIMINARY

POWER MANAGEMENT

Typical Applications (Cont.)

Bill of Material for Isolated Application (Cont.)

Item

Qty Reference

Part Number/Value

Manufacturing

40.2k, 1%, 1206, 1/8W

200, 5%, 1206, 1/8W

Any

R10,R28

R11

R12

R15

R21

R26

R27

R31

R33

1.00k, 1%, 1206, 1/8W

6.04k, 1%, 1206, 1/8W

51.1k, 1%, 1206, 1/8W

10.0, 5%, 1206, 1/8W

Any

4.99k, 1%, 1206, 1/8W

34.0k, 1%, 1206, 1/8W

11.0k, 1%, 1206, 1/8W

Any

10k, 5%, 1206, 1/8W

Any

33.2, 1%, 1206, 1/8W

Any

E-I Core - Main Transformer

6-Layer FR-4 PCB, Main Transformer

Current Sensor Transformer, 1:100

Magnetics. P/N: R-41805-E&I

Any

Panasonic: P/N: TJ0042T

Semtech P/N: SC4820B

Push-Pull Controller for Isolated Power

Supplies

Surface Mount Optocouplers

Shunt Regulator

Any. MOC206-M

Semtech P/N: SC4431CSK.5

Semtech P/N: SC431LCSK-.5

Low Voltage Adjustable Shunt Reg.

Notes:

1. * indicates optional parts.

2. Some parts are selected due to availability or lead time, and are not optimized.

www.semtech.com

2001 Semtech Corp.

SC4820

Push-Pull Controller

ꢀor Isolated Power Supplies

PRELIMINARY

POWER MANAGEMENT

Typical Applications (Cont.)

NON-ISOLATED APPLICATION - 48V Input, 3.3V/10A Output. Using SC4820A

www.semtech.com

2001 Semtech Corp.

SC4820

Push-Pull Controller

ꢀor Isolated Power Supplies

PRELIMINARY

POWER MANAGEMENT

Electrical Characteristic Curves

All of the characteristic curves are:

1. ꢀor isolated application with 36 ~ 75V input, 5V/10A output, and 500kHz switching frequency

2. Tested at 25°C ambient temperature.

Typical output ripple voltage at 48V input and full load

Output Volage (50 mV/div)

Time (1 us/div)

Typical start-up at 48V input and full load

Output Volage (1 V/div)

Time (5 ms/div)

www.semtech.com

2001 Semtech Corp.

SC4820

Push-Pull Controller

ꢀor Isolated Power Supplies

PRELIMINARY

POWER MANAGEMENT

Electrical Characteristic Curves (Cont.)

Typical transient response to step increase in load from 50% to 75% of full load at 0.1A/µs slew rate and 48V

input.

Output Voltage (100 mV/div)

Output Current (2 A/div)

Time (100 us/div)

Typical transient response to step decrease in load from 50% to 25% of full load at 0.1A/µs slew rate and 48V input.

Output Voltage (100 mV/div)

Output Current (2 A/div)

Time (100 us/div)

www.semtech.com

2001 Semtech Corp.

SC4820

Push-Pull Controller

ꢀor Isolated Power Supplies

PRELIMINARY

POWER MANAGEMENT

Outline Drawing - S0-8

Land Pattern - S0-8

Contact Information

Semtech Corporation

Power Management Products Division

652 Mitchell Rd., Newbury Park, CA 91320

Phone: (805)498-2111 ꢀAX (805)498-3804

www.semtech.com

2001 Semtech Corp.

SC4820AISTR [SEMTECH]

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