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HIGH SPEED, 100V, SELF OSCILLATING 50% DUTY CYCLE,
HALF-BRIDGE DRIVER
Package
IR2085S & (PbF)
Data Sheet No. PD60206 Rev.C
Simplified Circuit Diagram
Product Summary
www.irf.com
1
V
b
GND
LO
HO
V
s
Cs
OSC
V
cc
R
D
C
S
R1
S
R2
V
o
R
C
L
I
R
208
5
Vbias (10-15V)
S
S
C
2
C
1
1
2
Vin ( 100V max)
T
C
T
C
BIAS
BOOT
BOOT
V
b
GND
LO
HO
V
s
Cs
OSC
V
cc
R
D
C
S
R1
S
R2
V
o
R
C
L
I
R
208
5
Vbias (10-15V)
S
S
C
2
C
1
1
2
Vin ( 100V max)
T
C
T
C
BIAS
BOOT
BOOT
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
V
CC (max)
25V
V
offset(max)
100Vdc
High/low side
output freq (f
osc
) 500kHz
Output Current (I
O
)
+/-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.
Each channel frequency is equal to f
osc
, where f
osc
can be set by selecting R
T
& C
T
,
where f
osc
1/(2*R
T
.C
T
). Dead-time can be controlled through proper selection of C
T
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 V
CC
is less than 7.5Vdc.
S O -8
S O -8
2
IR2085S & (PbF)
www.irf.com
Absolute Maximum Ratings
Absolute maximum ratings indicate sustained limits beyond which damage to the device may occur. All voltage param-
eters 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
High side floating supply voltage
-0.3
150
V
CC
Low side supply voltage
--
25
V
S
High side floating supply offset voltage
V
b
- 25
V
b
+ 0.3
V
HO
High side floating output voltage
V
b
- 0.3
V
b
+ 0.3
V
LO
Low side output voltage
-0.3
V
CC
+ 0.3
OSC
OSC pin voltage
-0.3
V
CC
+ 0.3
V
CS
Cs pin voltage
-0.3
V
CC
+ 0.3
dV
S
/dt
Allowable offset voltage slew rate
-50
+50
V/ns
I
CC
Supply current
--
20
mA
P
D
Package power dissipation
--
1.0
W
Rth
JA
Thermal resistance, junction to ambient
--
200
C/W
T
J
Junction temperature
-55
150
T
S
Storage temperature
-55
150
T
L
Lead temperature (soldering, 10 seconds)
--
300
C
Recommended Operating Conditions
For proper operation the device should be used within the recommended conditions.
Vb
High side floating supply voltage
V
dd
-0.7
15
V
S
Steady state high side floating supply offset voltage
-5
100
V
CC
Supply voltage
10
15
I
CC
Supply current (Note 2)
--
5
mA
R
T
Timing resistor
10
100
K
C
T
Timing capacitor
47
1000
pF
fosc(max)
Operating frequency (per channel)
-- 500
KHz
T
J
Junction temperature
-40
125
C
Vdc
Symbol
Definition
Min.
Max.
Units
Note1: Care should be taken to avoid output switching conditions where the Vs node flies inductively below ground by more
than 5V.
V
3
IR2085S & ( PbF)
www.irf.com
Static Electrical Characteristics
V
BIAS
(V
CC
, V
BS
) = 12V, C
LOAD
= 1000 pF and T
A
= 25
C unless otherwise specified.
Symbol
Definition
Min.
Typ. Max. Units Test Conditions
V
OH
High level output voltage, (V
BIAS
- V
O
)
--
--
1.5
V
OL
Low level output voltage
--
--
0.1
Ileak
Offset supply leakage current
--
--
50
I
QBS
Quiescent V
BS
supply current
--
--
150
I
QCC
Quiescent V
CC
supply current
--
--
1.5
mA
V
CS+
Overcurrent shutdown threshold
250
300
350
mV
V
CS-
Overcurrent shutdown threshold
150
200
250
mV
U
VCC+
Undervoltage positive going threshold
6.8
7.3
7.8
U
VCC-
Undervoltage negative going threshold
6.3
6.8
7.3
U
VBS+
High side undervoltage positive going threshold
6.8
7.3
7.8
U
VBS-
High side undervoltage negative going threshold
6.3
6.8
7.3
I
O+
Output high short circuit current
--
1.0
--
I
O-
Output low short circuit current
--
1.0
--
Dynamic Electrical Characteristics
V
BIAS
(V
CC
, V
BS
) = 12V, C
LOAD
= 1000 pF, and T
A
= 25
C unless otherwise specified.
V
A
Symbol
Definition
Min. Typ.
Max. Units Test Conditions
tr
Turn-on rise time
--
40
60
tf
Turn-off fall time
--
20
30
fosc
Per channel output frequency
500
--
--
KHz
tdt
High/low output dead time
50
--
--
tdcs
Overcurrent shut down delay
--
200
--
pulse on CS
PM
High/low pulse width mismatch
-25
--
25
V
S
= 0V ~ 100V
nsec
V
S
= 0V
nsec
C
T
=100pF,
R
T
=10Kohm
V
A
4
IR2085S & (PbF)
www.irf.com
Lead Assignments
Functional Block Diagrams
Lead Definitions
Symbol Description
VCC
Logic supply
GND
Logic supply return
Vb
High side floating supply
VS
Floating supply return
HO
High side output
LO
Low side output
CS
Current sense input
OSC
Oscillator pin
Vb
HO
VS
LO
IR2085S
VCC
OSC
CS
GND
1
2
3
8
7
6
5
4
UVLO
BIAS
OSC
BLOCK
PULSE
STEERING
+
OVC
-
UVLO
AND
RS
LATCH
SOFT
START
10PF
VCC
VREF
(250mV)
VCC
Vb
HO
VS
LO
CT
GND
IR2085S
BLOCK
DIAGRAM
CS
OSC
RT
Also available LEAD-FREE (PbF)
5
IR2085S & ( PbF)
www.irf.com
Fig. 1 Typical Output Frequency (-25
o
C to 125
o
C)
Fig. 2 Typical Dead Time (@25
o
C)
Fig. 3 Typical Dead Time vs Temperature
0
50
100
150
200
250
300
350
400
450
500
10
20
30
40
50
60
70
80
90
100
RT (kohms)
Fr
e
que
nc
y
(
k
H
z
)
C
T
= 47pF
C
T
= 100pF
C
T
= 220pF
C
T
= 470pF
50
75
100
125
150
175
200
225
250
10
20
30
40
50
60
70
80
90
100
RT (kohms)
Ti
m
e
(
n
s
)
C
T
= 470pF
C
T
= 220pF
C
T
= 100pF
C
T
= 47pF
60
80
100
120
140
160
180
-40
-20
0
20
40
60
80
100
120
Temperature
Dead Time (ns)
DT(CT=100pF, RT=100k)
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