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 SI4728CY
Vishay Siliconix
N-Channel Synchronous MOSFETs with Break-Before-Make
FEATURES
D D D D 4.5- to 30-V Operation Driver Impedance--3 W Undervoltage Lockout Fast Switching Times (30 ns typ.) D D D D 30-V MOSFETs High Side: 0.018 W @ VDD = 4.5 V Low Side: 0.0105 W @ VDD = 4.5 V Switching Frequency: 250 kHz to 1 MHz
DESCRIPTION
The SI4728CY n-channel synchronous MOSFET with break-before-make (BBM) is a high speed driver designed to operate in high frequency dc-dc switchmode power supplies. It's purpose is to simplify the use of n-channel MOSFETs in high frequency buck regulators. This device is design to be used with any single output PWM IC or ASIC to produce a highly efficient low cost synchronous rectifier converter. A synchronous enable pin (disable = low, enable = high) controls the synchronous function for light load conditions. The SI4728CY is packaged in Vishay Siliconix's high performance LITTLE FOOTR SO-16 package.
FUNCTIONAL BLOCK DIAGRAM
4.5 V to 30 V
5V
VDD
Si4728
CBOOT D1
Q1 MOSFET Drive Circuitry with Break-BeforeMake S1 D2
CBOOT VOUT +
SYNC EN DC-DC Controller
IN GND
Q2 S2 GND
GND
Document Number: 71286 S-03075--Rev. C, 03-Feb-03
www.vishay.com
1
SI4728CY
Vishay Siliconix
ABSOLUTE MAXIMUM RATINGS (TA = 25_C UNLESS OTHERWISE NOTED)
Parameter
Logic Supply Logic Inputs Drain-Source Voltage Bootstrap Voltage Synchronous Pin Voltage Maximum Power Dissipationa Driver Operating Junction and Storage Temperature Range MOSFETs Tj, Tstg
Symbol
VDD VIN VDS VBOOT VSYNC PD
Steady State
7 - 0.7 to VDD + 0.3 - 1.0 to 30 7 - 0.7 to VDD +0.3 4 - 65 to 125 - 65 to 150
Unit
V
W _C _
Notes a. Surface mounted on 1" x1" FR4 board, full copper two sides. b. Pulse test: pulse width v300 mS, duty cycle v2%. Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
RECOMMENDED OPERATING CONDITIONS
Parameter
Drain Voltage Logic Supply Input Logic High Voltage Input Logic Low Voltage Bootstrap Capacitor Ambient Temperature
Symbol
VD1 VDD VIH VIL CBOOT TA
Steady State
4.5 to 30 4.5 to 5.5 0.7 VDD to VDD VDD
Unit
V
- 0.3 to 0.3
100 n to 1 m - 40 to 85
F _C
THERMAL RESISTANCE RATINGS
Parameter
Highside Junction-to-Ambienta Lowside Junction-to-Ambienta Highside Junction-to-Foot (Drain)b Steady State
Symbol
RthJA1 RthJA2 RthJF1 RthJF2
Typical
85 68 24 16
Maximum
105 85 30 20
Unit
_C/W _
Lowside Junction-to-Foot (Drain)b
Notes a. Surface Mounted on 1" x 1" FR4 Board. b. Junction-to-foot thermal impedance represents the effective thermal impedance of all heat carrying leads in parallel and is intended for use in conjunction with the thermal impedance of the PC board pads to ambient (RthJA = RthJF + RthPCB-A). It can also be used to estimate chip temperature if power dissipation and the lead temperature of a heat carrying (drain) lead is known.
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Document Number: 71286 S-03075--Rev. C, 03-Feb-03
SI4728CY
Vishay Siliconix
SPECIFICATIONS
Test Conditions Unless Specified Parameter Power Supplies
Logic Voltage Logic Current VDD IDD(EN) IDD(DIS) VDD = 4.5 V, VIN = 4.5 V VDD = 4.5 V, VIN = 0 V 4.5 280 220 5.5 500 500 V mA m
Limits Min Typ Max Unit
Symbol
TJ = 25_C 4.5 V < VDD < 5.5 V, 4.5 V < VD1 < 30 V
Logic Input
High Logic Input Voltage (VIN) Low VIH VIL 3.15 VDD = 4.5 V - 0.3 2.3 2.25 0.8 V
Protection
Break-Before-Make Reference Undervoltage Lockout Undervoltage Lockout Hysteresis VBBM VUVLO VH VDD = 5.5 V SYNC = 4.5 V 3.75 2.4 4 0.4 4.25 V
MOSFET Drivers
Driver Impedance RDR1 RDR2 Driver 1 VDD = 4.5 V Driver 2 3.6 2 W
MOSFETs
Drain-Source Voltage Drain-Source On-State Resistancea Diode Forward Voltagea VDS rDS(on)1 rDS(on)2 VSD1 VSD2 ID = 250 mA VDD = 4.5 V, ID = 10 A TJ = 25_C IS = 2 A, VGS = 0 V Q1 Q2 Q1 Q2 30 13 8 0.7 0.7 18 10.5 1.1 1.1 V V mW W
Dynamicb (Unless Specified--Fs = 250 kHz, dc = 10%. VDD = 5 V, I = 10 A, Refer to Switching Test Setup)
Rise Time trdr1 trdr2 tfdr1 tfdr2 td(off)1 td(off)2 Dt1-2 Dt2-1 tr tf tfr2 10% - 90% 90% - 10% IF 2.7 A, di/dt = 100 A/ms See Timing Diagram Driver 1 10% - 90% Driver 2 Driver 1 90% - 10% Driver 2 VIN to G1 VIN to G2 G1 to G2 G2 to G1 S1/D2 S1/D2 31 23 9 15 50 27 19 38 29 10 50 60 40 20 40 100 60 40 80 60 20 80 ns
Fall Time
Turn-Off Delay Dt D Rise Time Fall Time Source-Drain Reverse Recovery Time--Q2
Notes a. Pulse test: pulse width v300 ms; duty cycle v 2%. b. Typical values are for DESIGN AID ONLY, not guaranteed nor subject to production testing.
Document Number: 71286 S-03075--Rev. C, 03-Feb-03
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3
SI4728CY
Vishay Siliconix
DETAILED BLOCK DIAGRAM
VDD CBOOT VDC VOUTH Level Shift VS Undervoltage Lockout VDD IN SYNC EN VOUTL S1 D2
Q1
Q2
+ GND
VBBM
FIGURE 1.
PIN CONFIGURATION
SO-16
D1 D1 GND IN SYNC EN S2 S2 S2 1 2 3 4 5 6 7 8 Top View Order Number: SI4728CY 16 15 14 13 12 11 10 9 S1 S1 CBOOT VDD D2 D2 D2 D2
TRUTH TABLE
Sync EN
H H L L
VIN
H L H L
Q1
ON OFF ON OFF
Q2
OFF ON OFF OFF
PIN DESCRIPTION
Pin Number
1, 2 3 4 5 6, 7, 8 9, 10, 11, 12 13 14 15, 16 www.vishay.com
Symbol
D1 GND IN SYNC EN S2 D2 VDD CBOOT S1 Ground
Description
Highside MOSFET Drain
Input Logic Signal Synchronous Enable Lowside MOSFET Source Lowside MOSFET Drain Logic Supply Bootstrap Capacitor For Upper MOSFET Highside MOSFET Source Document Number: 71286 S-03075--Rev. C, 03-Feb-03
4
SI4728CY
Vishay Siliconix
TIMING DIAGRAM
VIN VIN
G1
G2
G2
G1
td(off) output (S1/D2, not to scale)
dt1- 2
td(off)
dt2-1
output (S1/D2, not to scale)
FIGURE 2. Dt1-2
FIGURE 3. Dt2-1
SWITCHING TEST SETUP
20 V C VDD 5V D1 C G1 CBOOT MOSFET Drive Circuitry with Break-BeforeMake S1 G2 D2 S1/D2 CL S2 GND + RL L CBOOT
SYNC EN
IN Signal Input GND
GND
FIGURE 4.
Document Number: 71286 S-03075--Rev. C, 03-Feb-03
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5
SI4728CY
Vishay Siliconix
TYPICAL CHARACTERISTICS (25_C UNLESS NOTED)
On-Resistance vs. Gate-to-Source Voltage (Q1)
100 80
On-Resistance vs. Gate-to-Source Voltage (Q2)
r DS(on) - On-Resistance (M W )
80
r DS(on) - On-Resistance (M W )
60 ID = 10 A 40
60
ID = 10 A
40
20
20
0 0 2 4 6 8 10 VGS - Gate-to-Source Voltage (V)
0 0 2 4 6 8 10 VGS - Gate-to-Source Voltage (V)
Output Capacitance vs. Drain Voltage (Q1)
2000 3000 1600 2400 C oss (pF) 1200 C oss (pF)
Output Capacitance vs. Drain Voltage (Q2)
1800
800 1200 400
600
0 0 6 12 18 24 30
0 0 6 12 18 24 30
VDS - Drain-to-Source Voltage (V)
VDS - Drain-to-Source Voltage (V)
On-Resistance vs. Junction Temperature
1.6 VGS = 4.5 V ID = 10 A Q2 2.30 Q1 2.25 Input V IH (V) 1.2 2.20 2.15 2.10 0.6 2.05 2.00 - 50 2.35
Input VIH vs. Junction Temperature
VDD = 4.5 V
r DS(on) - On-Resistance (W) (Normalized)
1.4
1.0
0.8
0.4 - 50
- 25
0
25
50
75
100
125
150
- 25
0
25
50
75
100
125
150
TJ - Junction Temperature (_C)
TJ - Junction Temperature (_C)
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6
Document Number: 71286 S-03075--Rev. C, 03-Feb-03
SI4728CY
Vishay Siliconix
TYPICAL CHARACTERISTICS (25_C UNLESS NOTED)
Input Current vs. Junction Temperature
350 10
Source-Drain Diode Forward Voltage
300 ( mA) IDDQ @ IN = H 250 I S - Source Current (A)
I DDQ
200 IDDQ @ IN = L 150
TJ = 150_C
TJ = 25_C
100 - 50
- 25
0
25
50
75
100
125
150
1 0.2
0.3
0.4
0.5
0.6
0.7
0.8
TJ - Junction Temperature (_C)
VSD - Source-to-Drain Voltage (V)
Single Pulse Power, Junction-to-Foot (Q1)
50 50
Single Pulse Power, Junction-to-Ambient (Q1)
40
40
Power (W)
20
Power (W)
30
30
20
10
10
0 0.01
0.1
1
10
100
1000
0 0.01
0.1
1
10
100
1000
Time (sec)
Time (sec)
Single Pulse Power, Junction-to-Foot (Q2)
50 50
Single Pulse Power, Junction-to-Ambient (Q2)
40
40
Power (W)
20
Power (W)
30
30
20
10
10
0 0.01
0.1
1
10
100
1000
0 0.01
0.1
1
10
100
1000
Time (sec)
Time (sec)
Document Number: 71286 S-03075--Rev. C, 03-Feb-03
www.vishay.com
7
SI4728CY
Vishay Siliconix
TYPICAL CHARACTERISTICS (25_C UNLESS NOTED)
Normalized Thermal Transient Impedance, Junction-to-Ambient (Q1)
2 1 Normalized Effective Transient Thermal Impedance Duty Cycle = 0.5
0.2
Notes:
0.1 0.1 0.05
t1 PDM
0.02
t2 1. Duty Cycle, D =
2. Per Unit Base = RthJA = 85_C/W
t1 t2
Single Pulse 0.01 10 -4 10 -3 10 -2 10 -1 1 Square Wave Pulse Duration (sec)
3. TJM - TA = PDMZthJA(t) 4. Surface Mounted
10
100
600
2 1 Normalized Effective Transient Thermal Impedance Duty Cycle = 0.5
Normalized Thermal Transient Impedance, Junction-to-Foot (Q1)
0.2 0.1 0.1 0.05 0.02
Single Pulse 0.01 10 -4 10 -3 10 -2 10 -1 1 10 Square Wave Pulse Duration (sec)
2 1 Normalized Effective Transient Thermal Impedance Duty Cycle = 0.5
Normalized Thermal Transient Impedance, Junction-to-Ambient (Q2)
0.2
Notes:
0.1 0.1 0.05
t1 PDM
0.02
t2 1. Duty Cycle, D =
t1 t2 2. Per Unit Base = RthJA = 68_C/W 3. TJM - TA = PDMZthJA(t) 4. Surface Mounted
Single Pulse 0.01 10 -4 10 -3 10 -2 10 -1 1 Square Wave Pulse Duration (sec)
10
100
600
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8
Document Number: 71286 S-03075--Rev. C, 03-Feb-03
SI4728CY
Vishay Siliconix
TYPICAL CHARACTERISTICS (25_C UNLESS NOTED)
Normalized Thermal Transient Impedance, Junction-to-Foot (Q2)
2 1 Normalized Effective Transient Thermal Impedance Duty Cycle = 0.5
0.2 0.1 0.1 0.05 0.02
Single Pulse 0.01 10 -4 10 -3 10 -2 10 -1 1 10
Document Number: 71286 S-03075--Rev. C, 03-Feb-03
www.vishay.com
9


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