A Product Line of
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 turn-
off time 20ns
Suitable for Discontinuous Mode (DCM),
Critical Conduction Mode (CrCM) and
Continuous conduction mode (CCM)
operation
Compliant with Energy Star V2.0 and
European Code of Conduct V3
Low component count
Halogen free
5-15V V
CC
range
Applications
Flyback converters in:
•
•
•
•
Adaptors
LCD monitors
Server PSU’s
Set top boxes
•
•
•
•
Refer to documents; AN54, DN90, DN91 and
DN94 available from the website
Pin out detail
Typical configuration
Transformer
N/C
REF
GATEL
GATEH
1
2
3
4
8
7
6
5
DRAIN
BIAS
R
RE F
R
B IA S
R EF
BIAS
Vcc
GND
V
CC
D R AIN
ZX G D
3101
C1
GAT EL GAT EH GN D
SM8
S yn ch ro n o u s R e ctifie r
M O S FE T
Ordering information
Device
ZXGD3101T8TA
Status
Active
Package
SM8
Part Mark
ZXGD3101
Reel size
(inches)
7
Tape width
(mm)
12
Quantity
per reel
1000
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ZXGD3101T8
Absolute maximum ratings
Parameter
Supply voltage
1
Continuous Drain pin voltage
1
GATEH and GATEL output Voltage
1
Driver peak source current
Driver peak sink current
Reference current
Bias voltage
Bias current
Power dissipation at T
A
=25°C
Operating junction temperature
Storage temperature
Symbol
V
CC
V
D
V
G
I
SOURCE
I
SINK
I
REF
V
BIAS
I
BIAS
P
D
T
j
T
stg
Limit
15
-3 to180
-3 to V
CC
+ 3
4
7
25
V
CC
100
500
-40 to +150
-50 to +150
Unit
V
V
V
A
A
mA
V
mA
mW
°C
°C
NOTES:
1. All voltages are relative to GND pin
Thermal resistance
Parameter
Junction to ambient
(*)
Junction to lead
(†)
Symbol
R
θJA
R
θIA
Value
250
54
Unit
°C/W
°C/W
NOTES:
(*) 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
ESD Rating
Model
Human body
Machine
Rating
4,000
400
Unit
V
V
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ZXGD3101T8
Electrical characteristics at T
A
= 25°C;
V
CC
= 10V; R
BIAS
= 1.8kΩ; R
REF
=3kΩ
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Unit
Input and supply characteristics
Operating current
Gate Driver
Turn-off Threshold
Voltage
(**)
I
OP
V
DRAIN
≤
-200m V
V
DRAIN
≥
0V
-
-
3
8
-
-
mA
V
T
V
G(off)
V
G
= 1V,
(*)
V
DRAIN
≥
0V,
(*)
V
DRAIN
= -60mV,
(†)
-45
-
5.0
7.0
8.4
9.2
9.3
-16
0.6
7.5
8.5
9
9.4
9.5
2.5
2.5
525
0
1
-
-
mV
GATE output voltage
(**)
V
G
V
DRAIN
= -80mV,
(†)
V
DRAIN
= -100mV,
(†)
V
DRAIN
≤
-140mV,
(†)
V
DRAIN
≤
-200mV,
(†)
V
-
-
-
-
-
A
A
ns
ns
ns
ns
GATEH peak source current
GATEL peak sink current
Turn on Propagation delay
Turn off Propagation delay
Gate rise time
Gate fall time
NOTES:
I
SOURCE
I
SINK
t
d1
t
d2
t
r
t
f
V
GH
= 1V
V
GL
= 5V
C
L
= 2.2nF,
(†)
(a)
15
305
20
(**) GATEH connected to GATEL
(*) R
H
= 100KΩ, R
L
= 0/C
(†)
R
L
= 100KΩ, R
H
= 0/C
(a) (Refer to Fig 4; Test circuit and Fig 5; Timing diagram on page 11
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ZXGD3101T8
Schematic symbol and pin description
Vcc
+
H igh V o lt
G ate D rive C ontrol
-
+
-
com parator
GATEH
D river
H igh V o lt
com parator
D R A IN
T urn-on/off C ontrol
GATEL
T hreshold V oltage
C ontrol
REF
B IA S
GND
Pin No.
1
2
Symbol
NC
REF
Description and function
No connection
This pin can be connected to GND
Reference
This pin is connected to V
CC
via resistor, R
REF
. R
REF
should be selected to source
~3mA into this pin. See note 1
Gate turn off
This pin sinks current, I
SINK
, from the synchronous MOSFET Gate.
Gate turn on
This pin sources current, I
SOURCE
, to the synchronous MOSFET Gate.
Power Supply
This is the supply pin. It is recommended to decouple this point to ground
closely with a ceramic capacitor.
Ground
This is the ground reference point. Connect to the synchronous MOSFET Source
terminal.
Bias
This pin is connected to V
CC
via resistor, R
BIAS
. R
BIAS
should be selected to
source 1.6 times I
REF
into this pin. See note 1
Drain connection
This pin connects directly to the synchronous MOSFET Drain terminal.
3
4
5
GATEL
GATEH
V
CC
6
GND
7
BIAS
8
DRAIN
NOTES:
1. BIAS and REF pins should be assumed to be at GND+0.7V
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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.
Body D iode
2
C onduction
M OSF ET
D rain Voltage
1
D rain
current
zero
6
M OSF ET
Gate Voltage
M OSF ET
Gate C urrent
3
4
5
7
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