irs27951s International Rectifier Corp., irs27951s Datasheet - Page 10

• Manufacturer Part Number: irs27951s
• Description: Resonant Half-bridge Converter Control Ic
• Manufacturer: International Rectifier Corp.

Lead Definitions
Lead Assignments
VCC: Power Supply Voltage
This is the supply voltage pin of the IC and sense node for the under-voltage lock out circuit. It is possible to turn
off the IC by pulling this pin below the minimum turn off threshold voltage, V
is not internally clamped.
RT: Oscillator timing resistor
This pin provides a precise 2V reference and a resistor connected from this pin to COM defines a current that is
used to set the minimum oscillator frequency. To close the feedback loop that regulates the converter output voltage
by modulating the oscillator frequency, the phototransistor of an optocoupler will be connected to this pin through a
resistor. The value of this resistor will set the maximum operating frequency. An R-C series connected from this pin
to COM sets frequency shift at start-up to prevent excessive energy inrush (soft-start).
CT/SD: Oscillator timing capacitor /Shutdown
An external capacitor CT from this pin to COM sets the dead time and frequency of the oscillator. The CT pin has
sawtooth waveform, which is charged up by the current reference programmed at RT pin during rising slope and is
discharged by an internal fixed 2mA current source during the falling slope. The falling time of the sawtooth defines
the dead-time.
At start-up, a 10uA current source charges this capacitor and the oscillator is enabled only when the voltage at this
pin exceeds VEN1. The IC can also be used to enter sleep mode by externally pulling this pin below VEN2.
COM: Logic and Gate drive Ground
This is ground potential pin of the integrated control circuit. All internal circuits are referenced to this point.
Symbol
www.irf.com
CT/SD
COM
VCC
HO
RT
LO
VS
VB
Supply Voltage
Oscillator timing resistor
Oscillator timing capacitor / shutdown
Ground
Low-side gate drive
High-side gate drive return / HV current Sense
High-side gate drive
High-side floating supply voltage
1
2
3
4
CT/SD
VCC
COM
RT
Description
10
VB
HO
VS
LO
8
7
6
5
CCUV-
without damage to the IC. This pin
© 2010 International Rectifier
IRS27951S
IRS27952S