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Data Sheet No. PD60206 Rev.C
IR2085S & (PbF)
HIGH SPEED, 100V, SELF OSCILLATING 50% DUTY CYCLE, HALF-BRIDGE DRIVER
Features
* * * * * * * * * *
Simple primary side control solution to enable half-bridge DC-Bus Converters for 48V distributed systems with reduced component count and board space. Integrated 50% duty cycle oscillator & half-bridge driver IC in a single SO-8 package Programmable switching frequency with up to 500kHz max per channel +/- 1A drive current capability optimized for low charge MOSFETs Adjustable dead-time 50nsec - 200nsec Floating channel designed for bootstrap operation up to +100Vdc High and low side pulse width matching to +/- 25nsec Adjustable overcurrent protection Undervoltage lockout and internal soft start Also available LEAD-FREE
Product Summary
VCC (max) 25V 100Vdc Voffset(max) High/low side output freq (fosc) 500kHz Output Current (IO) +/-1.0A(typ.) High/low side pulse width matching +/- 25ns
Description
The IR2085S is a self oscillating half-bridge driver IC with 50% duty cycle ideally suited for 36V-75V half-bridge DC-bus converters. This product is also suitable for push-pull converters without restriction on input voltage.
Package
Each channel frequency is equal to fosc, where fosc can be set by selecting RT & CT, S O -8 where fosc 1/(2*RT.CT). Dead-time can be controlled through proper selection of CT and can range from 50 to 200nsec. Internal soft-start increases the pulse width during power up and maintains pulse width matching for the high and low outputs throughout the start up cycle. The IR2085S initiates a soft start at power up and after every overcurrent condition. Undervoltage lockout prevents operation if VCC is less than 7.5Vdc.
Simplified Circuit Diagram
Vbias (10-15V) D BOOT C BOOT Vin ( 100V max)
Vcc
Vb
HO
S1
C2
IR2085
RT CT C BIAS
OSC
S R1 L S R2
C
R Vo
Vs
Cs
GND
LO
S2
C1
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IR2085S & (PbF)
Absolute Maximum Ratings
Absolute maximum ratings indicate sustained limits beyond which damage to the device may occur. All voltage parameters are absolute voltages referenced to COM. All currents are defined positive into any lead. The thermal resistance and power dissipation ratings are measured under board mounted and still air conditions.
Symbol
Vb VCC VS VHO VLO OSC VCS dVS/dt ICC PD RthJA TJ TS TL
Definition
High side floating supply voltage Low side supply voltage High side floating supply offset voltage High side floating output voltage Low side output voltage OSC pin voltage Cs pin voltage Allowable offset voltage slew rate Supply current Package power dissipation Thermal resistance, junction to ambient Junction temperature Storage temperature Lead temperature (soldering, 10 seconds)
Min.
-0.3 -- Vb - 25 Vb - 0.3 -0.3 -0.3 -0.3 -50 -- -- -- -55 -55 --
Max.
150 25 Vb + 0.3 Vb + 0.3 VCC + 0.3 VCC + 0.3 VCC + 0.3 +50 20 1.0 200 150 150 300
Units
V
V/ns mA W C/W C
Recommended Operating Conditions
For proper operation the device should be used within the recommended conditions.
Symbol
Vb VS VCC ICC RT CT fosc(max) TJ
Definition
High side floating supply voltage Steady state high side floating supply offset voltage Supply voltage Supply current (Note 2) Timing resistor Timing capacitor Operating frequency (per channel) Junction temperature
Min.
Vdd -0.7 -5 10 -- 10 47 -- -40
Max.
15 100 15 5 100 1000 500 125
Units
Vdc mA K pF
KHz
C
Note1: Care should be taken to avoid output switching conditions where the Vs node flies inductively below ground by more than 5V.
2
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IR2085S & ( PbF)
Dynamic Electrical Characteristics
VBIAS (VCC, VBS) = 12V, CLOAD = 1000 pF, and TA = 25C unless otherwise specified.
Symbol
tr tf fosc tdt tdcs PM
Definition
Turn-on rise time Turn-off fall time Per channel output frequency High/low output dead time Overcurrent shut down delay High/low pulse width mismatch
Min.
-- -- 500 50 -- -25
Typ.
40 20 -- -- 200 --
Max. Units Test Conditions
60 30 -- -- -- 25 nsec nsec KHz VS = 0V CT =100pF, RT =10Kohm pulse on CS VS = 0V ~ 100V
Static Electrical Characteristics
VBIAS (VCC, VBS) = 12V, CLOAD = 1000 pF and TA = 25C unless otherwise specified.
Symbol
VOH VOL Ileak IQBS IQCC VCS+ VCSUVCC+ UVCCUVBS+ UVBSIO+ IO-
Definition
High level output voltage, (VBIAS - VO) Low level output voltage Offset supply leakage current Quiescent VBS supply current Quiescent VCC supply current Overcurrent shutdown threshold Overcurrent shutdown threshold Undervoltage positive going threshold Undervoltage negative going threshold High side undervoltage positive going threshold High side undervoltage negative going threshold Output high short circuit current Output low short circuit current
Min. Typ. Max. Units Test Conditions
-- -- -- -- -- 250 150 6.8 6.3 6.8 6.3 -- -- -- -- -- -- -- 300 200 7.3 6.8 7.3 6.8 1.0 1.0 1.5 0.1 50 150 1.5 350 250 7.8 7.3 7.8 7.3 -- -- A V V A mA mV mV
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IR2085S & (PbF)
Functional Block Diagrams
VCC
IR2085S BLOCK DIAGRAM UVLO BIAS
Vb
RT
OSC CT
OSC BLOCK PULSE STEERING SOFT START
UVLO AND RS LATCH
HO
VS VCC
CS
+ OVC VREF (250mV)
LO 10PF
GND
Lead Definitions
Symbol Description
VCC GND Vb VS HO LO CS OSC Logic supply Logic supply return High side floating supply Floating supply return High side output Low side output Current sense input Oscillator pin
Lead Assignments
1 CS Vb 8
2
OSC
HO
7
IR2085S
3
GND
VS
6
4
LO
VCC
5
Also available LEAD-FREE (PbF)
4
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IR2085S & ( PbF)
500 450 400
250 225 200
350 Frequency (kHz) 300 250 200 CT = 47pF 150 100 50 0 10 20 30 40 50 60 RT (kohms) 70 80 90 100 CT = 470pF CT = 220pF CT = 100pF
175 Time (ns) 150
CT = 470pF
CT = 220pF 125 100 75 50 CT = 100pF CT = 47pF
10
20
30
40
50
60
70
80
90
100
RT (kohms)
Fig. 1 Typical Output Frequency (-25oC to 125oC)
Fig. 2 Typical Dead Time (@25oC)
180
160
140 Dead Time (ns)
120
100
DT(CT=100pF, RT=100k)
80
60 -40 -20 0 20 40 60 80 100 120 Temperature
Fig. 3 Typical Dead Time vs Temperature
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IR2085S & (PbF)
Pin descriptions
CS: The input pin to the overcurrent comparator. Exceeding the overcurrent threshold value specified in static electrical parameters section will terminate the output pulses and start a new soft-start cycle as soon as the voltage on the pin reduces below the threshold value. OSC: The oscillator-programming pin. Only two components are required to program the oscillator frequency, a resistor (tied to the VCC and CS pins), and a capacitor (tied to the CS and GND pins). The approximate oscillator frequency is determined by the following simple formula: fOSC = 1/ (2*RT.CT) Where fOSC frequency is in hertz (Hz), RT resistance in ohms () and CT capacitance in farads (F). The recommended range for the timing resistor is between 10kW and 100kW and the recommended range for the timing capacitor is between 47pF and 470pF. It is not recommended to use timing resistors less than 10k. For best performance, keep the timing component placement as close as possible to the IR2085S. It is recommended to separate the ground and VCC traces to the timing components. GND: Signal ground and power ground for all functions. Due to high current and high frequency operation, a low impedance circuit board ground plane is highly recommended. HO, LO: High side and low side gate drive pins. The high and low side drivers can be used to drive the gate of a power MOSFET directly, without external buffers. The drivers are capable of 1.2A peak source and sink currents. It is recommended that the high and low side drive pins should be located very close to the gates of the high side and low side MOSFETs to prevent any delay and distortion of the drive signals. The power MOSFETs should be low charge to prevent any shoot through current.
Vb: The high side power input connection. The high side supply is derived from a bootstrap circuit using a low-leakage schottky diode and a ceramic capacitor. To prevent noise, the schottky diode and bypass capacitor should be located very close to the IR2085S and separated VCC traces are recommended. VS: The high side power return connection. VS should be connected directly to the source terminal of the high side MOSFET with the trace as short as possible. VCC: The IC bias input connection for the device. Although the quiescent VCC current is very low, total supply current will be higher, depending on the MOSFET gate charge connected to the HO and LO pins, and the programmed oscillator frequency. Total VCC current is the sum of quiescent VCC current and the average current at HO and LO. Knowing the operating frequency and the MOSFET gate charge (QG), the average current can be calculated from: Iave = QG X fosc To prevent noise problems, a bypass ceramic capacitor connected to VCC and GND should be placed as close as possible to the IR2085S. The IR2085S has an under voltage lockout feature for the IC bias supply, VCC. The minimum voltage required on VCC to make sure that the IC will work within specifications is 9.5V. Asymmetrical gate signals on HO and LO pins are expected when VCC is between 7.5V and 8.5V.
Application Information
A 220 kHz half-bridge application circuit with full wave synchronous rectification is shown in figure 4. On the primary side, the IR2085S drives two IRF7493 - next generation low charge power MOSFETs. The primary side bias is obtained through a linear regulator from the input voltage for start-up, and then from the transformer in steady state. The IRF7380, a dual 80V power MOSFET in an SO8 package is used for the primary side bias function. Two IRF6603 - novel DirectFET
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IR2085S & ( PbF)
power MOSFETs are used on the secondary side in a self-driven synchronous rectification topology. DirectFETs practically eliminate MOSFET packaging resistance, which maximizes circuit efficiency. The DirectFET construction includes a copper "clip" across the backside of the silicon, which enables top-sided cooling and improved thermal performance. The DirectFET gate drive voltage is clamped to an optimum value of 7.5V with the IRF9956 dual SO-8 MOSFET. The secondary side bias scheme is designed to allow outputs of two bus converters to be connected in parallel, while operating from different input voltages, and also to allow continuing output current if one of the two input sources is shorted or disconnected.
200 200 36~60Vinput 39k 7 3V 15V rm Vdd 36~60Vinput IRF7493 Vdd 7 IRF7380
Two ferrite cores are used for the transformer and inductor. The transformer core is a PQ20/16 (3F3) with 3:1 turns ratio and 1mil gap. The inductor core is an E14/3.5/5 (3F3) with one turn and a 5mil gap. The PCB has eight layers, with two layers for primary windings that are connected in parallel and each has three turns. Four layers are used for the secondary windings. Each layer has one turn and two layers are connected in parallel to get two sets of secondary windings. 4 oz Cu PCB is recommended for the primary and secondary windings. Each primary side winding is placed between the two sets of the secondary windings to balance the secondary side current.
.1u
39k
9 9
9V
.1u
100k
22u 22u 3 IRF6603 1u 3.3u 1 IR2085S cs ct G LO Vb HO Vs Vcc 1u 1u 1 Vdd 3.3u IRF7493 3 IRF6603 10k 3 IRF9956 10k
6~10Vout
56k
56k
47 47p
Figure 4 - IR2085S DC Bus converter reference design.
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IR2085S & (PbF)
Case outline
D A 5 B
FOOTPRINT 8X 0.72 [.028]
DIM A b c D
INCHES MIN .0532 .013 .0075 .189 .1497 MAX .0688 .0098 .020 .0098 .1968 .1574
MILLIMETERS MIN 1.35 0.10 0.33 0.19 4.80 3.80 MAX 1.75 0.25 0.51 0.25 5.00 4.00
A1 .0040
6 E
8
7
6
5 H 0.25 [.010] A
E
6.46 [.255]
1
2
3
4
e e1 H K L
8X 1.78 [.070]
.050 BASIC .025 BASIC .2284 .0099 .016 0 .2440 .0196 .050 8
1.27 BASIC 0.635 BASIC 5.80 0.25 0.40 0 6.20 0.50 1.27 8
6X
e e1
3X 1.27 [.050]
y
A C 0.10 [.004] y
K x 45
8X b 0.25 [.010]
A1 CAB
8X L 7
8X c
NOTES: 1. DIMENSIONING & TOLERANCING PER ASME Y14.5M-1994. 2. CONTROLLING DIMENSION: MILLIMETER 3. DIMENSIONS ARE SHOWN IN MILLIMETERS [INCHES]. 4. OUTLINE C ONFORMS TO JEDEC OUTLINE MS-012AA.
5 DIMENSION DOES NOT INCLUDE MOLD PROTRUSIONS. MOLD PROTRUSIONS NOT TO EXCEED 0.15 [.006]. 6 DIMENSION DOES NOT INCLUDE MOLD PROTRUSIONS. MOLD PROTRUSIONS NOT TO EXCEED 0.25 [.010]. 7 DIMENSION IS THE LENGTH OF LEAD FOR SOLDERING TO A SUBSTRATE.
8-Lead SOIC
01-6027 01-0021 11 (MS-012AA)
8
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IR2085S & ( PbF)
LEADFREE PART MARKING INFORMATION
Part number
IRxxxxxx YWW? ?XXXX
Lot Code (Prod mode - 4 digit SPN code) IR logo
Date code
Pin 1 Identifier ? P MARKING CODE Lead Free Released Non-Lead Free Released
Assembly site code Per SCOP 200-002
ORDER INFORMATION
Basic Part (Non-Lead Free) 8-Lead SOIC IR2085S order IR2085S Leadfree Part 8-Lead SOIC IR2085S order IR2085SPBF
This product has been designed and qualified for the industrial market. Qualification Standards can be found on IR's Web Site http://www.irf.com/. Data and specifications subject to change without notice
WORLD HEADQUARTERS: 233 Kansas Street, El Segundo, California 90245 Tel: (310) 252-7105 11/9/2004
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