Diodes ZXGD3103N8 User Manual

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ZXGD3103N8

SYNCHRONOUS MOSFET CONTROLLER

Description

The ZXGD3103 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.

Features

• Proportional Gate Drive

• Turn-off propagation delay 15ns and turn-off

time 20ns.

• Detector threshold voltage ~10mV

• Standby current 5mA

• Suitable for Discontinuous Mode (DCM),

Critical Conduction Mode (CrCM) and
Continuous Mode (CCM) operation

• 5-15V V

range

CC

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.

Applications

• Flyback Converters in:

• Adaptors

• LCD Monitors

• Server PSU’s

• Set Top Boxes

• LCD TV

• Resonant Converters

• LED TV

• High power Adaptors

• Street Lighting

• ATX psu

Pin out details

Typical Configuration

SO-8

Ordering information

Device Status Package Part Mark

Reel size

(inches)

Tape width

(mm)

Quantity per reel

ZXGD3103N8TC Production SO8 ZXGD3103 13 12 2500

Marking information

ZXGD

3103
Y W

ZXGD = Product Type Marking Code, Line 1
3103 = Product Type Marking Code, Line 2
YY = Year (ex: 11 = 2011)
WW = Week (01 - 53)

ZXGD3103N8

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Absolute maximum ratings

Parameter Symbol Limit Unit

Supply voltage1 V
Continuous Drain pin voltage1 V
GATEH and GATEL output Voltage1 V
Driver peak source current I
Driver peak sink current I
Reference current I
Bias voltage V
Bias current I
Power dissipation at TA =25°C

15 V

CC

-3 to180 V

D

-3 to V

G

2.5 A

SOURCE

6 A

SINK

25 mA

REF

V

BIAS

100 mA

BIAS

P

490 mW

D

+ 3 V

CC

V

CC

Operating junction temperature Tj -40 to +150
Storage temperature T

Notes: 1. All voltages are relative to GND pin.

-50 to +150

stg

Thermal resistance

°C
°C

Parameter Symbol Value Unit

Junction to ambient (a) R

Junction to lead (b) R

Notes: a. Mounted on minimum 1oz weight copper on FR4 PCB in still air conditions.

b. Output Drivers - Junction to solder point at end of the lead 5 and 6

255 °C/W

θJA

120 °C/W

θlA

ESD Rating

Model Rating Unit

Human Body 2000 V
Machine 300 V

ZXGD3103N8

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Electrical characteristics at TA = 25°C; VCC = 10V; R

Parameter Symbol Conditions Min. Typ. Max. Unit
Input and supply characteristics

≤ -200m V - 2.16 -

V

Operating current IOP

Gate Driver

Turn-off Threshold
Voltage(**)

V

T

V

G(off)

GATE output voltage (**)

VG

D

VD ≥ 0V - 5.16 -

V

= 1V, (*)

G

V

≥ 0V, (*)

D

= -50mV, (g)

V

D

VD = -100mV, (g)
VD ≤ -150mV, (g)

= 3.3kΩ; R

BIAS

= 4.3kΩ

REF

mA

-16 -10 0 mV

- 0.73 1

6.0 7.2 -

8.8 9.2 -

V

9.2 9.4 -

VD ≤ -200mV, (g)

9.3 9.5 -

Switching performance (“) for QG(tot) = 82nC

Turn on Propagation delay t
Turn off Propagation delay td2 15

d1

Refer to switching waveforms
in Fig. 3

150

Gate rise time tr 450
Gate fall time tf

Notes:

(**) GATEH connected to GATEL
(*) R

= 100kΩ, RL = O/C

H

= 100kΩ, RH = O/C

(g) R

L

Continuous Conduction Mode
Discontinuous Conduction

Mode

21

17

(“) refer to test circuit below

ns

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Schematic Symbol and Pin Out Details

Pin No. Name Description and function

1
2

3 GATEL

4

NC No Internal connection
REF

Reference

This pin is connected to V

Gate turn off

GATEH

This pin sinks current, I

Gate turn on

This pin sources current, I

SINK

Power Supply

5 VCC

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

Ground

6 GND

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

7 BIAS

8

DRAIN

Bias

This pin is connected to V

Drain connection

This pin connects directly to the synchronous MOSFET Drain terminal.

via resistor, R

CC

REF

, from the synchronous MOSFET Gate.

, to the synchronous MOSFET Gate.

SOURCE

via resistor, R

CC

BIAS

.

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Typical Characteristics

14
12
10

8
6
4

Gate Voltage (V)

G

V

2

See Resistor Table for Values

0

-100 -80 -60 -40 -20 0

VD Drain Voltage (mV)

Transfer Characteristic

5

0

-5

-10

-15

VCC = 10V
R
R
VG = 1V
100k pull up

VCC = 15V
VCC = 12V
VCC = 10V
VCC = 5V

=3K3

BIAS

=4K3

REF

10

8

6

4

VCC = 10V
R

=3K3

Gate Voltage (V)

G

V

BIAS

2

R

=4K3

REF

100k pull down

0

-100 -80 -60 -40 -20 0

VD Drain Voltage (mV)

Transfer Characteristic

100

10

VCC = 10V
R

=3k3

BIAS

R

=4K3

REF

D = 0.5

C

=22nF

LOAD

C

=10nF

LOAD

C

=4.7nF

LOAD

C

=2.2nF

LOAD

C

=1nF

LOAD

T = -40°C
T = 25°C
T = 85°C
T = 125°C

Drain Voltage (mV )

-20

D

V

-25

-50 -25 0 25 50 75 100 125 150

Temperature (°C)

Drain Sense Voltage vs Temperature

100

R

=3k3

BIAS

R

80

60

40

20

=4K3

REF

D = 0.5
f=250kHz

Supply Current (mA )

0

0 2 4 6 8 10 12 14 16 18 20 22

VCC = 15V

VCC = 12V

VCC = 10V

VCC = 5V

Capacitance (nF)

Supply Current vs Capacitive Load

Supply Current (mA )

1k 10k 100k

Frequency (Hz)

Supply Current vs Frequency

1
0

-1

-2

-3

-4

Peak Current (A)

-5

Current flow Gate to Ground

0 5 10 15 20 25

Current flow Supply to Gate

Capacitance (nF)

Gate Current v s C ap a citive L o ad

VCC = 10V
R

=3K3

BIAS

R

=4K3

REF

T = 2 5°C

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Typical Characteristics

10

8
6
4

V

D

2

Voltage (V)

VCC=10V
R

V

G

BIAS

R

REF

C

LOAD

0

-2

-0.5 0.0 0.5 1.0 1.5

Time (μs)

Switch On Speed

0.3

0.2

0.1

Gate Current (A)

0.0

-0.5 0.0 0.5 1.0 1.5

Time (μs)

VCC=10V
R

=3k3

BIAS

R

=4K3

REF

C

=10nF

LOAD

Ga te Driv e On Current

=3k3

=4K3

=10nF

10

8
6
4

V

D

2

Voltage (V)

V

G

0

-2

-40 -20 0 20 40 60 80 100 120 140

Time (ns)

Switch Off Speed

2
1
0

-1

-2

Gate Current (A)

-3

-4

-40 -20 0 20 40 60 80 100 120 140

Time (ns)

Gate Drive O ff C u rrent

VCC=10V
R

BIAS

R

=4K7

REF

C

LOAD

VCC=10V
R

=3k3

BIAS

R

=4K3

REF

C

=10nF

LOAD

=10k

=10nF

6

4

VCC=10V
R

BIAS

R

REF

C

LOAD

2

0

-2

Percent Change Time (%)

-50 -25 0 25 50 75 100 125 150

Switching vs Temp erature

ZXGD3103N8

Document number: DS32255 Rev. 2 - 2

=3k3

=4K3

=10nF

tON= tD + t

t

Temperature (°C)

R

= tD + t

OFF

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Application information

The purpose of the ZXGD3103 is to drive a MOSFET as a low-VF Schottky diode replacement in offline
power converters. When combined with a low R
improvement, whilst maintaining design simplicity and incurring minimal component count. Figure 1 and 2
show typical configuration of ZXGD3103 for synchronous rectification in a Flyback and a multiple output
resonant converter.

MOSFET, it can yield significant power efficiency

DS(ON)

Figure 1. Example connections in Flyback supply

Figure 2. Example connections in LLC supply

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Descriptions of the normal operation

The operation of the device is described step-by-step with reference to the timing diagram in Figure 3.

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 -

0.8V 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 GATE pin.

4. The controller goes into proportional gate drive control — the GATE output voltage is proportional to the
on-resistance-induced Drain-Source voltage drop across the MOSFET. Proportional gate drive ensures that
MOSFET conducts for majority of the conduction cycle and minimizes body dio de conduction time.

5. As the Drain current decays linearly toward zero, proportional gate drive control reduces the Gate voltage
so the MOSFET can be turned off rapidly at zero current crossing. The GATE voltage is removed when the
Drain-Source voltage crosses the detection threshold voltage to minimize reverse current flow.

6. At zero Drain current, the controller GATE output voltage is pulled low to V

to ensure that the

G(off)

MOSFET is off.
Figure 4 shows typical operating waveforms for ZXGD3103 driving a MOSFET with Q

Flyback converter operating in critical conduction mode.

= 82nC in a

g(TOT)

Figure 3. Timing diagram for a critical conduction mode Flyback converter

ZXGD3103N8

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Typical waveforms

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Fig 4a: Critical conduction mode

Switch O n S peed

10

9
8
7
6
5
4
3
2

Voltage (V)

1
0

-1

-2

V

D

-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

V

G

VCC = 10V
R

= 3K3

BIAS

= 4K3

R

REF

= 82nC

Q

g(TOT)

Time (μs)

Fig 4b: Typical switch ON speed when driving a Q

Switch O FF S peed

10

9
8
7
6
5
4
3
2

Voltage (V)

1
0

-1

-2

-0.05 -0.04 -0.03 -0.02 -0.01 0.0 0 0.01 0.02 0.03 0.04 0 .05

V

D

Time (μs)

V

G

VCC = 10V
R

= 3K3

BIAS

R

= 4K3

REF

Q

g(TOT)

g(TOT)

= 82nC

= 82nC MOSFET

Fig 4c: Typical switch OFF speed when driving a Q

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= 82nC MOSFET

g(TOT)

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Design considerations

It is advisable to decouple the ZXGD3103 closely to VCC and ground due to the possibility of high peak gate
currents with a 1μF X7R type ceramic capacitor as shown in Figure 2. The Gate pins should be as close to
the MOSFET’s gate as possible. Also the ground return loop should be as short as possible.

To minimize parasitic inductance-induced premature turn-off issue of the synchronous controller always
keep the PCB track length between ZXGD3101’s Drain input and MOSFET’s Drain to less than 10mm. Low
internal inductance MOSFET packages such as SO-8 and PolarPak are also recommended for high
switching frequency power conversion to minimize body diode conduction.

R1, Q1 D1 and C1 in Figure 1 are only required as a series drop-down regulator to maintain a stable Vcc
around 10V from a power supply output voltage greater than 15V.

External gate resistors are optio nal. They can be inserted to control the rise and fall time which may help
with EMI issues.

The proper selection of external resistors R
Select a value for resistor R
typical ZXGD3103’s detection threshold voltage of 10mV.

REF

and R

BIAS

and R

REF

from Table 1 based on the desired Vcc value. This provides the

BIAS

Table 1. Recommended resistor values for various supply voltages

VCC R

5V 1K6 2K0
10V 3K3 4K3
12V 3K9 5K1
15V 5K1 6K8

BIAS

is important to the optimum device operation.

R

REF

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Package Outline and Dimensions

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IMPORTANT NOTICE

LIFE SUPPORT

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