IRS2980STRPBF International Rectifier, IRS2980STRPBF Datasheet - Page 12

• Manufacturer Part Number: IRS2980STRPBF
• Description: An LED Driver Control IC
• Manufacturer: International Rectifier

Specifications of IRS2980STRPBF

• Package: 8-lead SOIC
• Circuit: LED Driver
• Offset Voltage (v): 600
• Output Source Current Min (ma): 180
• Output Sink Current Min (ma): 260
• Pbf: Yes
• T R (ns): 120
• T F (ns): 50

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Operating frequency and duty cycle will vary when
there is ripple in the DC bus voltage. For example
where a passive valley fill circuit is used for power
factor correction (PFC) the LED current will be
regulated dynamically by constantly changing
frequency and duty cycle to maintain a constant
average.
Current Sense Filter Selection
The recommended values for R
100Ohms and 1nF. This is sufficient to prevent
instability due to switching noise appearing at the
current sense input. These values have negligible
effect on the frequency and ripple. In a test
application using a 3.3mH inductor to drive a
17.5V LED panel, the output current varied from
338mA to 347mA (2.7%) over a DC voltage input
range of 40V to 200V.
A resistor (RG) between the gate driver output
and the gate of the power MOSFETs is also
recommended to reduce switching transients by
reducing dv/dt. A value of 10Ohms is
recommended, however this can be increased to
reduce noise if required.
Filter values may be increased in order to lower
the running frequency without increasing inductor
size. This results in higher current ripple and
higher current change over input voltage
variations. This may be an acceptable
compromise depending on the application
specification.
Frequency Limiter
The switching frequency of the IRS2980S is
internally limited to approximately 150 kHz (f
The IRS2980S is designed for use below this
frequency in order to limit current consumption in
the VCC and floating high side bias supplies. This
is necessary because the IRS2980S uses internal
regulators to supply these voltages, which can
supply only a limited current. This restriction is
acceptable in most LED driver applications.
Where higher frequency operation is needed the
IRS25401/11 is recommended.
High Voltage Regulator
The IRS2980S includes a high voltage regulator
to supply VCC from the DC input bus voltage.
This eliminates the need for external VCC supply
circuitry. A VCC capacitor of 1uF is recommended
for reliable startup and smooth operation. The
IRS2980S may shut down if CVCC is not present
or too small.
If necessary the internal regulator may also be
bypassed by supplying an external DC supply
from 14V to 15V to the VCC pin. Although the HV
F
and C
F
are
MAX
).
12
pin of the IRS2980S is rated up to 450V, the
actual maximum voltage that can be applied is
limited by the by the power dissipation of the IC.
The internal VCC regulator is recommended for
use up to 200VDC or with a passive valley fill PFC
circuit operating from up to 250VAC input. It can
be operated at higher voltages only with sufficient
heat sinking.
Figure 2: Passive valley fill PFC circuit
Figure 3: Passive valley fill PFC bus voltage (blue)
and line input current (red) waveforms.
The VCC current (ICC) drawn by the IRS2980S
can be estimated from the following formula:
Therefore power dissipation due to the high
voltage regulator can be calculated as:
Floating Differential Current Sense
The floating high side current sense incorporated
in the IRS2980S is able to operate up to 450V and
withstand voltage surges up to 600V. An internal
bias supply is derived between the HV and VS
I
P
CC
REG
≈ 1
=
mA
V
BUS
+
_
Q
DC
G
_
⋅
AV
f
SW
⋅
I
CC
© 2011 International Rectifier
IRS2980S