IRS25411SPBF International Rectifier, IRS25411SPBF Datasheet - Page 12

• Manufacturer Part Number: IRS25411SPBF
• Description: IC LED CONS CURR CTRL 8SOIC
• Manufacturer: International Rectifier

Specifications of IRS25411SPBF

• Internal Driver: No
• Type - Primary: General Purpose
• Mounting Type: Surface Mount
• Topology: PWM, Step-Down (Buck)
• Number Of Outputs: 1
• Frequency: 500kHz
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• No. Of Outputs: 1
• Output Current: 700mA
• Output Voltage: 16.6V
• Input Voltage: 8V To 16.6V
• Dimming Control Type: PWM
• Operating Temperature Range: -55°C To +150°C
• Driver Case Style: SOIC
• Rohs Compliant: Yes
• Package: 8-lead SOIC
• Circuit: Half-Bridge Driver
• Offset Voltage (v): 600
• Output Source Current Min (ma): 500
• Output Sink Current Min (ma): 700
• Output Voltage Min (v): 8
• Output Voltage Max (v): 16.6
• Pbf: Yes
• V Bsuv+ (v): 7.5
• V Bsuv- (v): 7.0
• V Ccuv+ (v): 9.0
• V Ccuv- (v): 7.5
• T On (ns): 320
• T Off (ns): 180
• T R (ns): 50
• T F (ns): 30
• Dt (ns): 140
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Supply: -
• Voltage - Output: -
• Operating Temperature: -
• Lead Free Status / Rohs Status: Supplier Unconfirmed

www.irf.com
As long as V
the watchdog timer described below, which maintains
charge for the floating high side on the bootstrap
capacitor. The load is receiving current from V
which simultaneously stores energy in the inductor, as
V
V
after the delay t
turn on after the deadtime (DT), the inductor then
releases its stored energy into the load and V
decreasing. When V
control loop switches HO on after the delay t
LO off after the delay t
continues to regulate the current at an average value
Application Information and Additional
Details
Operating Mode
The IRS254(01,11) operates as a time-delayed
hysteritic buck controller. During normal operating
conditions the output current is regulated via the IFB
pin voltage (nominal value of 500 mV). This feedback
is compared to an internal high precision bandgap
voltage reference. An on-board dV/dt filter has also
been used to ignore erroneous transitioning.
Once the supply to the IC reaches V
output is held high and the HO output low for a
predetermined period of time. This initiates charging of
the bootstrap capacitor, establishing the V
supply for the high-side output. The IC then begins
toggling HO and LO outputs as needed to regulate the
current.
IFB
IFB
crosses V
increases, unless the load is open circuit. Once
Fig.1 IRS254(01,11) Control Signals, Iavg=1.2 A
IFB
IFBTH
is below V
HO,OFF
, the control loop switches HO off
IFB
. When HO switches off, LO will
drops below V
IFBTH
HO,ON
, HO is on, modulated by
+ DT. The switching
IFBTH
CCUV+
again, the
BS
HO,ON
,
Iout
HO
LO
IFB
the LO
floating
starts
and
BUS
12
,
The control method is hysteretic with a free running
frequency, which enables average current regulation
in constrast to a fixed frequency scheme providing
peak current regulation only. This reduces the part
count since there is no need for frequency setting
components and also provides an inherently stable
system, which acts as a dynamic current source.
A deadtime of approximately 140 ns between the two
gate drive signals is incoporated to prevent shoot-
through. The deadtime has been adjusted to maintain
precise current regulation, while still preventing
shoot-through.
determined as follows. When the inductance value
is large enough to maintain a low ripple on I
can be calculated:
IFB
HO
LO
IFBTH
50%
Fig.3 IRS254(0,1) Time Delayed Hysterisis
(B) Releasing Inductor Stored Energy
Fig.2 (A) Storing Energy in Inductor
(A)
Iout
(
t_HO_off
avg
t_LO_on
IRS254(0,1)(S)PbF
)
50%
DT1
=
VIFBTH
50%
© 2010 International Rectifier
t_LO_off
t_HO_on
50%
50%
DT2
RCS
(B)
FB
, I
out,avg