IR2166
oscillate at the preheat frequency with 50% duty
cycle and with a dead-time which is set by the
value of the external timing capacitor, CT, and
internal deadtime resistor, RDT. Pin CPH is
disconnected from COM and an internal 3µA
current source (Figure 3)
VCC is the dead-time (both off) of the output
gate drivers, HO and LO. The selected value of
CT together with RDT therefore program the
desired dead-time (see Design Equations, page
26, Equations 1 and 2). Once CT discharges
below 1/3 VCC, MOSFET S3 is turned off,
disconnecting RDT from COM, and MOSFET
S1 is turned on, connecting RT and RPH again
to VCC. The frequency remains at the preheat
frequency until the voltage on pin CPH exceeds
10V and the IC enters Ignition Mode. During the
preheat mode, the over-current protection
together with the fault counter are enabled. The
peak ignition current must not exceed the
maximum allowable current ratings of the output
stage MOSFETs. Should this voltage exceed the
internal threshold of 1.3V, the internal FAULT
Counter begins counting the sequential over-
current faults (See Timing Diagram). If the
number of over-current faults exceed 25, the IC
will enter FAULT mode and gate driver outputs
HO, LO and PFC will be latched low.
VBUS (+)
HO
RT
M1
16
3
OSC.
RT
Half-
Bridge
Output
S4
Half-
Bridge
Driver
RPH
CT
4
5
VS
LO
R PH
15
11
ILOAD
CT
M2
3uA
CPH
RCS
2
CCPH
COM
12
IR2166
Load
Return
VBUS (-)
Figure 3, Preheat circuitry.
charges the external preheat timing capacitor
on CPH linearly. The over-current protection on
pin CS is disabled during preheat. The preheat
frequency is determined by the parallel
combination of resistors RT and RPH, together
with timing capacitor CT. CT charges and
discharges between 1/3 and 3/5 of VCC (see
Timing Diagram, page 9). CT is charged
exponentially through the parallel combination
of RT and RPH connected internally to VCC
through MOSFET S1. The charge time of CT
from 1/3 to 3/5 VCC is the on-time of the
respective output gate driver, HO or LO. Once
CT exceeds 3/5 VCC, MOSFET S1 is turned
off, disconnecting RT and RPH from VCC. CT is
then discharged exponentially through an
internal resistor, RDT, through MOSFET S3 to
COM. The discharge time of CT from 3/5 to 1/3
V
BUS (+)
VCC
13
3
S1
HO
VS
RT
16
15
M1
OSC
RT
Half-
Bridge
Output
S4
RPH
Half-
Bridge
Driver
4
5
RPH
ILOAD
CT
Fault
Logic
CT
LO
CS
11
10
M2
S3
1.3V
3uA
R1
CCS
Comp 4
CPH
2
RCS
CCPH
12
COM
IR2166
Load
Return
VBUS (-)
Figure 4, Ignition circuitry.
20
www.irf.com
INFINEON [ Infineon ]
