Diodes ZXGD3101T8 User Manual

A Product Line of

N/C

1

2

3

4

8

7

6

5

REF

GATEH

GATEL

DRAIN

BIAS

V

CC

GND

SM8

Diodes Incorporated

ZXGD3101T8

Synchronous rectifier controller for flyback converters.

Description

The ZXGD3101 is intended to drive MOSFETS configured as ideal diode replacements. The device is comprised of a differential amplifier detector stage and high current driver. The detector monitors the reverse voltage of the MOSFET such that if body diode conduction occurs a positive voltage is applied to the MOSFET's Gate pin.

Once the positive voltage is applied to the Gate the MOSFET switches on allowing reverse current flow. The detectors' output voltage is then proportional to the MOSFET Drain-Source reverse voltage drop and this is applied to the Gate via the driver. This action provides a rapid turn off as current decays.

Features

• Turn-off propagation delay 15ns and turnoff time 20ns

• Suitable for Discontinuous Mode (DCM), Critical Conduction Mode (CrCM) and Continuous conduction mode (CCM) operation

• Compliant with Energy Star V2.0 and

Applications

Flyback converters in:

• Adaptors

•LCD monitors

•Server PSU’s

• Set top boxes

European Code of Conduct V3

• Low component count

• Halogen free

•5-15V V

range

CC

Refer to documents; AN54, DN90, DN91 and DN94 available from the website

Pin out detail Typical configuration

Transformer

R

REF

DRAIN

GATEL

R

BIAS

Vcc

BIAS

ZXGD 3101

GATEH GND

C1

Synchronous Rectifier

MOSFET

Ordering information

Device Status Package Part Mark Reel size

(inches)

ZXGD3101T8TA Active SM8 ZXGD3101 7 12 1000

Issue 4 - January 2009 1 www.zetex.com

Tape width

(mm)

Quantity

per reel

ZXGD3101T8

NOTES:

Absolute maximum ratings

Parameter Symbol Limit Unit

Supply voltage

Continuous Drain pin voltage

GATEH and GATEL output Voltage

1

Driver peak source current I

Driver peak sink current I

Reference current I

Bias voltage V

Bias current I

Power dissipation at T

=25°CPD500 mW

A

Operating junction temperature T

Storage temperature T

NOTES:

1. All voltages are relative to GND pin

V

CC

V

D

V

G

SOURCE

SINK

REF

BIAS

j

stg

15 V

-3 to180 V

-3 to V

+ 3 V

CC

4A

7A

25 mA

V

CC

100 mA

-40 to +150 °C

-50 to +150 °C

Thermal resistance

Parameter Symbol Value Unit

V

Junction to ambient

Junction to lead

(*) Mounted on minimum 1oz copper on FR4 PCB in still air conditions (†) Output Drivers - Junction to solder point at end of the lead 5 and 6

(*)

(†)

R

θJA

θIA

250 °C/W

54 °C/W

ESD Rating

Model Rating Unit

Human body 4,000 V

Machine 400 V

Issue 4 - January 2009 2 www.zetex.com

ZXGD3101T8

Electrical characteristics at TA = 25°C;

VCC = 10V; R

Parameter Symbol Conditions Min. Typ. Max. Unit

Input and supply characteristics

Operating current

Gate Driver

Turn-off Threshold

Voltage

(**)

GATE output voltage

= 1.8kΩ; R

BIAS

(**)

REF

=3kΩ

V

T

V

I

OP

G(off)

V

G

V

DRAIN

≤ -200m V

≥ 0V

VG = 1V,

V

DRAIN

≥ 0V,

= -60mV,

= -80mV,

= -100mV,

≤ -140mV,

≤ -200mV,

(*)

(†)

-3 -

-8 -

-45 -16 0 mV

-0.6 1

5.0 7.5 -

7.0 8.5 -

8.4 9 -

9.2 9.4 -

9.3 9.5 -

mA

V

GATEH peak source current

GATEL peak sink current

Turn on Propagation delay

Turn off Propagation delay

Gate rise time

Gate fall time

NOTES:

(**) GATEH connected to GATEL

= 100KΩ, RL = 0/C

(*) R

H

(†) R

= 100KΩ, R

L

(a) (Refer to Fig 4; Test circuit and Fig 5; Timing diagram on page 11

= 0/C

H

I

SOURCE

I

SINK

t

d1

t

d2

t

r

t

f

= 1V

GH

V

= 5V

GL

CL = 2.2nF,

(†)

(a)

2.5 - A

525 ns

15 ns

305 ns

20 ns

Issue 4 - January 2009 3 www.zetex.com

Schematic symbol and pin description

High Volt

comparator

High Volt

comparator

Threshold Voltage

Control

Driver

+

-

DRAIN

GND

GATEH

GATEL

BIAS

REF

Gate Drive Control

Turn-on/off Control

Vcc

ZXGD3101T8

Pin No. Symbol Description and function

1 NC No connection

This pin can be connected to GND

2 REF Reference

This pin is connected to V ~3mA into this pin. See note 1

3 GATEL Gate turn off

This pin sinks current, I

4 GATEH Gate turn on

This pin sources current, I

5V

CC

Power Supply

This is the supply pin. It is recommended to decouple this point to ground closely with a ceramic capacitor.

6 GND Ground

This is the ground reference point. Connect to the synchronous MOSFET Source terminal.

7 BIAS Bias

This pin is connected to V source 1.6 times I

8 DRAIN Drain connection

This pin connects directly to the synchronous MOSFET Drain terminal.

SINK

into this pin. See note 1

REF

via resistor, R

CC

REF

. R

should be selected to source

REF

, from the synchronous MOSFET Gate.

SOURCE

CC

, to the synchronous MOSFET Gate.

via resistor, R

BIAS

. R

should be selected to

BIAS

NOTES:

1. BIAS and REF pins should be assumed to be at GND+0.7V

Issue 4 - January 2009 4 www.zetex.com

ZXGD3101T8

Operation

Normal Operation

The operation of the device is described step-by-step with reference to the timing diagram below.

1. The detector monitors the MOSFET Drain-Source voltage.

2. When, due to transformer action, the MOSFET body diode is forced to conduct there is

approximately -0.6V on the Drain pin.

3. The detector outputs a positive voltage with respect to ground, this voltage is then fed to the

MOSFET driver stage and current is sourced out of the GATEH pin.

4. The current out of the GATEH pin is sourced into the synchronous MOSFET Gate to turn the

device on.

5. The GATEH output voltage is now proportional to the Drain-Source voltage drop across the

MOSFET due to the current flowing through the MOSFET.

6. MOSFET conduction continues until the drain current reaches zero.

7. At zero current the detector output voltage is zero and the synchronous MOSFET Gate voltage

is pulled low by the GATEL, turning the device off.

MOSFET

Drain Voltage

MOSFET

Gate Voltage

MOSFET

Gate Current

Body Diode

Conduction

2

1

3

4

Drain

current

zero

6

5

7

Issue 4 - January 2009 5 www.zetex.com