Datasheet IR2085S Datasheet (International Rrectifier)

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HIGH SPEED, 100V, SELF OSCILLATING 50% DUTY CYCLE,

Data Sheet No. PD60206_B

IR2085S

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

•

Product Summary

V
V
High/low side

output freq (f
Output Current (I

High/low side pulse
width matching +/- 25ns

25V

CC (max)

offset(max)

100Vdc

) 500kHz

osc

+/-1.0A(typ.)

)

O

Package

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.

Each channel frequency is equal to f
f

≈ 1/(2*RT.CT). Dead-time can be controlled through proper selection of CT and can

osc

range from 50 to 200nsec. Internal soft-start increases the pulse width during power up and maintains pulse

, where f

osc

can be set by selecting RT & CT, where

osc

SO -8SO -8

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

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Vbias

C

BIAS

(10-15V)

R

T

C

T

C

D

BOOT

V

cc

OSC

BOOT

V

b

HO

s

V

IR2085S

GND

LO

Cs

Vin ( 100V max)

S

1

S

2

C

2

C

1

S

R1

L

S

R2

R

C

V

o

1

IR2085S

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 Definition Min. Max. Units

V

b

V

CC

V

S

V

HO

V

LO

OSC OSC pin voltage -0.3 VCC + 0.3

V

CS

dVS/dt Allowable offset voltage slew rate -50 +50 V/ns

I

CC

P

D

Rth

JA

T

J

T

S

T

L

High side floating supply voltage -0.3 150
Low side supply voltage — 25
High side floating supply offset voltage Vb - 25 Vb + 0.3
High side floating output voltage Vb - 0.3 V
Low side output voltage -0.3 VCC + 0.3

Cs pin voltage -0.3 VCC + 0.3

Supply current — 20 mA
Package power dissipation
Thermal resistance, junction to ambient — 200 °C/W
Junction temperature -55 150
Storage temperature -55 150
Lead temperature (soldering, 10 seconds) — 300

— 1.0 W

b

+ 0.3

°C

V

Recommended Operating Conditions

For proper operation the device should be used within the recommended conditions.

Symbol Definition Min. Max. Units

Vb High side floating supply voltage Vdd -0.7 15
V

S

V

CC

I

CC

R

T

C

T

fosc(max) Operating frequency (per channel) — 500

T

J

Note1: Care should be taken to avoid output switching conditions where the Vs node flies inductively below ground by more

than 5V.

2

Steady state high side floating supply offset voltage -5 100
Supply voltage 10 15
Supply current (Note 2) — 5 mA
Timing resistor 10 100 KΩ
Timing capacitor 47 1000 pF

Junction temperature -40 125 °C

Vdc

KHz

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IR2085S

Dynamic Electrical Characteristics

V

(VCC, VBS) = 12V, C

BIAS

Symbol Definition Min. Typ. Max. Units Test Conditions

t
t

fosc Per channel output frequency 500 — — K H z

tdt High/low output dead time 50 — —

t

dcs

PM High/low pulse width mismatch -25 — 25 VS = 0V ~ 100V

Turn-on rise time — 40 60

r

Turn-off fall time — 20 30

f

Overcurrent shut down delay — 200 — pulse on CS

Static Electrical Characteristics

V

(VCC, VBS) = 12V, C

BIAS

Symbol Definition Min. T yp. Max. Units T est Conditions

V

OH

V

OL

I

leak

I

QBS

I

QCC

V

CS+ Overcurrent shutdown threshold

V

CS- Overcurrent shutdown threshold

U

VCC+

U

VCC-

U

VBS+

U

VBS-

I

O+

I

O-

High level output voltage, (V
Low level output voltage — — 0.1
Offset supply leakage current — — 50
Quiescent VBS supply current — — 150
Quiescent VCC supply current — — 1.5 mA

Undervoltage positive going threshold 6.8 7.3 7.8
Undervoltage negative going threshold 6.3 6.8 7.3
High side undervoltage positive going threshold 6.8 7.3 7.8
High side undervoltage negative going threshold 6.3 6.8 7.3
Output high short circuit current — 1.0 —
Output low short circuit current — 1.0 —

= 1000 pF, and TA = 25°C unless otherwise specified.

LOAD

= 1000 pF and TA = 25°C unless otherwise specified.

LOAD

- VO) — — 1.5

BIAS

250 300 350 mV
150 200 250 mV

nsec

nsec

V

µA

V

A

VS = 0V

CT =100pF,

RT =10Kohm

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3

IR2085S

Functional Block Diagrams

RT

OSC

CT

VCC

CS

GND

UVLO BIAS

OSC

BLOCK

+

OVC

-

VREF

(250mV)

SOFT

START

10PF

IR2085S

BLOCK

DIAGRAM

PULSE

STEERING

UVLO

AND

RS

LATCH

Vb

HO

VS

VCC

LO

Lead Definitions

Symbol Description

V

CC

GND Logic supply return
Vb High side floating supply

V

S

HO High side output
LO Low side output
CS Current sense input
OSC Oscillator pin

4

Logic supply

Floating supply return

Lead Assignments

IR2085S

VCC

Vb

HO

VS

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CS

1

2

OSC

3

GND

LO

8

7

6

54

IR2085S

(

)

)

500

450

400

350

300

250

200

Frequency (kHz)

150

100

50

0

10 20 30 40 50 60 70 80 90 100

C

= 470pF

T

RT

C

= 220pF

T

kohms

C

= 100pF

T

CT = 47pF

Fig. 1 Typical Output Frequency (-25oC to 125oC)

180

160

250

225

200

175

150

Time (ns)

125

100

75

50

10 20 30 40 50 60 70 80 90 100

RT (kohms

CT = 470pF

C

= 220pF

T

C

= 100pF

T

C

= 47pF

T

Fig. 2 Typical Dead T ime (@25oC)

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140

120

Dead Time (ns)

100

DT(CT=100pF, RT=100k)

80

60

-40-200 20406080100120

Temperature

Fig. 3 Typical Dead Time vs Temperature

5

IR2085S

Pin descriptions

CS: The input pin to the overcurrent comparator. Ex-

ceeding 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:

f

= 1/ (2*RT.CT)

OSC

Where f
ohms (Ω) 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
10kΩ.

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.

frequency is in hertz (Hz), RT resistance in

OSC

V

: The high side power input connection. The high

b

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:

I

= QG X f

ave

osc

T o 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

6

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IR2085S

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

Vdd

36~60Vinput

1u

200

39k

3V

15V

rm

36~60Vinput

IRF7493

IRF7380

7

7

Vdd

3.3u

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.

9V

IRF6603

39k

.1u

100k

10k

22u

22u

6~10Vout

.1u

9
9

3

56k

6k

47

47p

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IR2085

cs
ct
G
LO Vcc

Vb

HO

Vs

S

1u

Vdd

IRF7493

1

1u

1

3.3u

3

IRF9956

3

IRF6603

10k

Figure 4 – IR2085S DC Bus converter reference design.

7

IR2085S

Case outline

A

E

D B

5

87

6

6X

0.25 [ . 010 ]

65

H

4312

0.25 [ . 010 ] A

e

8X b

e1

A1

A

CAB

NOTES:

1. DIMENSI ONING & TOLERANCING PER ASME Y14.5M-1994.

2. CONT ROLLING DIMENSION : MIL LIMET ER

3. D IMENSIONS ARE SHOWN IN MI LL IMETERS [INCHES].

4. OUTLI NE CONFORMS T O JEDE C OUT L INE MS-012AA .

C

0.10 [ . 004 ]

6.46 [. 2 55]

3X 1.27 [. 05 0]

y

8-Lead SOIC

DIM

FOOTPRINT

8X 0.72 [. 02 8]

8X 1.78 [. 07 0]

MIN MAX

A

.0532
A1
b
c .0075 .0098 0.19 0.25
D
E
e

e1

H
K
L
y

.0688

.0040

.0098

.013

.020

.189

.1968

.1497

.1574
.050 BASIC
.025 BASIC 0.635 BASIC
.2284

.2440
.0099

.0196
.016

.050

0°

K x 4 5°

8X L

8X c

7

5 DIMENSI ON D OES NOT INCLUDE MOLD PROT RUSIONS.
MOLD PROTRUSIONS NOT TO EXC EED 0.15 [.006].

6 DIMENSI ON D OES NOT INCLUDE MOLD PROT RUSIONS.
MOLD PROTRUSIONS NOT TO EXC EED 0.25 [.010].

7 DIMENSI ON IS T HE LENGTH OF LEAD FOR SOLDERING TO
A SUBSTRATE.

01-0021 11

8°

MILLIMETERSINCHES

MIN MAX

1.35

1.75

0.10

0.25

0.33

0.51

4.80

5.00

3.80

4.00

1.27 BASIC

5.80

6.20

0.25

0.50

0.40

1.27

0°

8°

01-6027

(MS-012AA)

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: [phone]

9/5/2003.

8

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