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A Product Line of Diodes Incorporated
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. 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
* * * * *
Applications
*
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 VCC range
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
N/C 1 REF 2
8 DRAIN 7 BIAS 6 GND 5 VCC
GATEL 3 GATEH 4
SO-8
Ordering information
Device Status Package SO8 Part Mark ZXGD3103 Reel size (inches) 13 Tape width (mm) 12 Quantity per reel 2500
ZXGD3103N8TC Production
ZXGD3103N8
Document number: DS32255 Rev. 2 - 2
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ZXGD3103N8
Absolute maximum ratings
Parameter Supply voltage1 Continuous Drain pin voltage1 GATEH and GATEL output Voltage1 Driver peak source current Driver peak sink current Reference current Bias voltage Bias current Power dissipation at TA =25C Operating junction temperature Storage temperature
Notes: 1. All voltages are relative to GND pin.
Symbol VCC VD VG ISOURCE ISINK IREF VBIAS IBIAS PD Tj Tstg
Limit 15 -3 to180 -3 to VCC + 3 2.5 6 25 VCC 100 490 -40 to +150 -50 to +150
Unit V V V A A mA V mA mW C C
Thermal resistance
Parameter Junction to ambient (a) Junction to lead (b)
Notes:
Symbol RJA RlA
Value 255 120
Unit C/W C/W
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
ESD Rating
Model Human Body Machine Rating 4000 400 Unit V V
ZXGD3103N8
Document number: DS32255 Rev. 1 - 2
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ZXGD3103N8
Electrical characteristics at TA = 25C; VCC = 10V; RBIAS = 3.3k; RREF= 4.3k
Parameter Symbol Conditions Min. Typ. Max. Unit
Input and supply characteristics Operating current Gate Driver Turn-off Threshold Voltage(**) VT VG(off) GATE output voltage (**) VG VG = 1V, (*) VD 0V, (*) VD = -50mV, ( ) VD = -100mV, ( ) VD -150mV, ( ) VD -200mV, ( ) -16 6.0 8.8 9.2 9.3 -10 0.73 7.2 9.2 9.4 9.5 0 1 V mV IOP VD -200m V VD 0V 2.16 5.16 mA -
Switching performance (") for QG(tot) = 82nC
Turn on Propagation delay Turn off Propagation delay Gate rise time Gate fall time td1 td2 tr tf Continuous Conduction Mode Discontinuous Conduction Mode
Notes: (**) GATEH connected to GATEL (*) RH = 100k, RL = O/C ( ) RL = 100k, RH = O/C
150 Refer to switching waveforms in Fig. 3 15 450 21 17 ns
(") refer to test circuit below
ZXGD3103N8
Document number: DS32255 Rev. 1 - 2
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ZXGD3103N8
Schematic Symbol and Pin Out Details
Pin No. 1 2 3 4 5
Name NC REF GATEL GATEH VCC
Description and function No Internal connection Reference This pin is connected to VCC via resistor, RREF Gate turn off This pin sinks current, ISINK, from the synchronous MOSFET Gate. Gate turn on This pin sources current, ISOURCE, 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 VCC via resistor, RBIAS. Drain connection This pin connects directly to the synchronous MOSFET Drain terminal.
6 7 8
GND BIAS DRAIN
ZXGD3103N8
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Typical Characteristics
14
10
VG Gate Voltage (V)
VG Gate Voltage (V)
12 10 8 6 4 2
See Resistor Table for Values
VCC = 15V VCC = 12V VCC = 10V VCC = 5V
8 6 4 2
VCC = 10V RBIAS=3K3 RREF=4K3 100k pull down
T T T T
= -40C = 25C = 85C = 125C
0 -100
-80
VD Drain Voltage (mV)
-60
-40
-20
0
0 -100
-80
-60
-40
-20
0
VD Drain Voltage (mV)
Transfer Characteristic
5 100
Transfer Characteristic
VD Drain Voltage (mV)
0 -5 -10 -15 -20 -25 -50
Supply Current (mA)
VCC = 10V RBIAS=3K3 RREF=4K3 VG = 1V 100k pull up
VCC = 10V RBIAS=3k3 RREF=4K3 D = 0.5
CLOAD=22nF CLOAD=10nF CLOAD=4.7nF CLOAD=2.2nF CLOAD=1nF
10
-25
0
25
50
75
100 125 150
1k
10k
100k
Temperature (C)
Frequency (Hz)
Drain Sense Voltage vs Temperature
100 1
RBIAS=3k3
Supply Current vs Frequency
Supply Current (mA)
Peak Current (A)
80 60 40
RREF=4K3 D = 0.5 f=250kHz
VCC = 15V VCC = 12V
0
Current flow Supply to Gate
-1 -2 -3 -4 -5 0
Current flow Gate to Ground VCC = 10V RBIAS=3K3 RREF=4K3 T = 25C
VCC = 10V
20
VCC = 5V
0 0 2 4 6 8 10 12 14 16 18 20 22 5 10 15 20 25
Capacitance (nF)
Capacitance (nF)
Supply Current vs Capacitive Load
Gate Current vs Capacitive Load
ZXGD3103N8
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Typical Characteristics
10 8
10 8
VCC=10V VG VD RBIAS=3k3 RREF=4K3 CLOAD=10nF
VCC=10V RBIAS=10k RREF=4K7 CLOAD=10nF
Voltage (V)
6 4 2 0 -2 -0.5 0.0 0.5
Voltage (V)
6 4 2 0
VD VG
1.0
1.5
-2
-40 -20
0
20 40 60 80 100 120 140
Time (s)
Time (ns)
Switch On Speed
0.3 2
Switch Off Speed
VCC=10V RBIAS=3k3 RREF=4K3 CLOAD=10nF
Gate Current (A)
Gate Current (A)
1 0 -1 -2 -3
VCC=10V RBIAS=3k3 RREF=4K3 CLOAD=10nF
0.2
0.1
0.0 -0.5 0.0 0.5 1.0 1.5
-4 -40 -20 0
20 40 60 80 100 120 140
Time (s)
Time (ns)
Gate Drive On Current
Percent Change Time (%)
VCC=10V RBIAS=3k3 RREF=4K3 CLOAD=10nF
Gate Drive Off Current
6 4 2
tON= tD + tR
tOFF= tD + tF
0 -2 -50
-25
0
25
50
75
100 125 150
Temperature (C)
Switching vs Temperature
ZXGD3103N8
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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 RDS(ON) MOSFET, it can yield significant power efficiency 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.
Figure 1. Example connections in Flyback supply
Figure 2. Example connections in LLC supply
ZXGD3103N8
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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 diode 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 VG(off) to ensure that the MOSFET is off. Figure 4 shows typical operating waveforms for ZXGD3103 driving a MOSFET with Qg(TOT) = 82nC in a Flyback converter operating in critical conduction mode.
Figure 3. Timing diagram for a critical conduction mode Flyback converter
ZXGD3103N8
Document number: DS32255 Rev. 1 - 2
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Typical waveforms
Fig 4a: Critical conduction mode
Sw itch On Speed
10 9 8 7 6 VD 5 VG 4 3 2 1 0 -1 -2 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8
Voltage (V)
VCC = 10V RBIAS = 3K3 RREF = 4K3 Qg(TOT) = 82nC
1.0 1.2 1.4 1.6
Tim (s) e
Fig 4b: Typical switch ON speed when driving a Qg(TOT) = 82nC MOSFET
Switch OFF Speed
10 9 8 7 6 5 4 3 2 1 0 -1 -2 -0.05 -0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04 0.05 VG VD VCC = 10V RBIAS = 3K3 RREF = 4K3 Qg(TOT) = 82nC
Voltage (V)
Time (s)
Fig 4c: Typical switch OFF speed when driving a Qg(TOT) = 82nC MOSFET
ZXGD3103N8
Document number: DS32255 Rev. 1 - 2
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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 1F 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 optional. They can be inserted to control the rise and fall time which may help with EMI issues. The proper selection of external resistors RREF and RBIAS is important to the optimum device operation. Select a value for resistor RREF and RBIAS from Table 1 based on the desired Vcc value. This provides the typical ZXGD3103's detection threshold voltage of 10mV.
Table 1. Recommended resistor values for various supply voltages
VCC 5V 10V 12V 15V RBIAS 1K6 3K3 3K9 5K1 RREF 2K0 4K3 5K1 6K8
ZXGD3103N8
Document number: DS32255 Rev. 1 - 2
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Package Outline and Dimensions
ZXGD3103N8
Document number: DS32255 Rev. 1 - 2
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