LT3485-0/LT3485-1/
LT3485-2/LT3485-3
13
34850123fb
APPLICATIO S I FOR ATIO
WUU
U
Table 4. Recommended IGBTs
DRIVE BREAKDOWN COLLECTOR
VOLTAGE VOLTAGE CURRENT
PART (V) (V) (PULSED) (A) VENDOR
CY25BAH-8F 2.5 400 150 Renesas
CY25BAJ-8F 4 400 150 (408) 382-7500
www.renesas.com
GT8G133 4 400 150 Toshiba Semiconductor
(949) 623-2900
www.semicon.toshiba.co.jp/eng/
the capacitance closest to the terminal goes low but the
capacitance further from the terminal remains high. This
causes a small portion of the device to handle the full 100A
of current, which quickly destroys the device. The pull
down circuitry needs to pull down slower than the internal
RC time constant in the gate of the IGBT. This is easily
accomplished with a resistor in series with the IGBT drive,
which is integrated into the LT3485.
The LT3485’s integrated drive circuit is independent of the
charging function. The IGBT section draws its power from
the IGBTPWR pin. The rise and fall times are measured
using a 4000pF output capacitor. The typical 10% to 90%
rise time is 270ns. The drive pulls high to IGBTPWR. The
typical 90% to 10% fall time is 180ns. The drive pulls
down to 300mV. The IGBT driver pulls a peak of 150mA
when driving an IGBT and 2mA of quiescent current. In the
low state, the IGBT’s quiescent current is less than 0.1µA.
Table 4 is a list of recommended IGBT devices for strobe
applications. These three devices are all packaged in
8-lead TSSOP packages.
V
OUT
Monitor
The voltage output monitor is a new feature to monitor the
progress of capacitor charging with a microcontroller.
The monitor uses the flyback waveform to output a
voltage proportional to the output of the flyback converter.
The output monitor voltage range for the pin is 0V to 1V.
The 1V output corresponds with the charge cycle termi-
nating and the DONE pin going low. The voltage output
monitor is only functional when the circuit is charging
(DONE and CHARGE are high.)
GATE
EMITTER
3485 F06
Figure 6. IGBT Gate
