IRS21571DSPBF International Rectifier, IRS21571DSPBF Datasheet - Page 22

• Manufacturer Part Number: IRS21571DSPBF
• Description: IC BALLAST CTRL 600V 16-SOIC
• Manufacturer: International Rectifier
• Type: Ballast Controllerr

Specifications of IRS21571DSPBF

• Frequency: 43.7 ~ 48.3 kHz
• Current - Supply: 10mA
• Current - Output: 180mA
• Voltage - Supply: 11.5 V ~ 15.6 V
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 16-SOIC (0.154", 3.90mm Width)
• Package: 16-lead SOIC Narrow
• Circuit: Fluorescent Ballast IC
• Offset Voltage (v): 600
• Output Source Current Min (ma): 180
• Output Sink Current Min (ma): 260
• Pbf: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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Half-Bridge Current Sensing and Protection
The third pin used for protection is the CS pin, which is normally connected to a resistor in the source of the lower
power MOSFET, as shown in Figure 14.
The CS pin is used to sense fault conditions such as failure of a lamp to strike, over-current during normal
operation, hard switching, no load, and operation below resonance. If any one of these conditions is sensed, the
fault latch is set, the oscillator is disabled, the gate driver outputs go low, and the chip is put into the micropower
mode. The CS pin performs its sensing functions on a cycle-by-cycle basis in order to maximize ballast reliability.
For the over-current, failure-to-strike, and hard switching fault conditions, an externally programmable, positive-
going CS+ threshold is enabled at the end of the preheat time. The level of this positive-going threshold is
determined by the value of the resistor R
For the under-current and under-resonance conditions, there is a negative-going CS- threshold of 0.2V which is
enabled at the onset of the run mode. The sensing of this CS- threshold is synchronized with the falling edge of
the LO output.
Figures 15, 16 and 17 are oscillographs of fault conditions. Figure 15 shows a failure of the lamp to strike, Figure
16 shows a hard switching condition and Figure 17 shows an under-current condition.
Figure 14: Half-bridge current sensing circuit connection (shaded area)
R
VDC
CPH
RPH
RUN
OC
OC
RT
CT
DT
1
2
3
4
5
6
7
8
OC
. The value of the resistor R
R
V
OC
CS +
16
15
14
13
12
11
10
9
VCC
COM
HO
CS
SD
VS
VB
LO
=
= 50E - 6 R
C
D
R
BOOT
BOOT
GHS
50E - 6
AC line
rectifie
R
V
GLS
d
22
R
C
SUPPLY
CS+
R3
VCC
D1
V
BUS
+V
BUS
return
,
Q1
Q2
R
CS
⋅
OC
or
C
D2
SNUBBER
1
OC
/
2
output
Bridge
is determined by the following formula:
© 2008 International Rectifier
IRS21571D