MC44603P ON Semiconductor, MC44603P Datasheet - Page 12
Manufacturer Part Number
Other Power Management Voltage/Current PWM
PWM Mode Controllerr
Specifications of MC44603P
Input Voltage Range
Package / Case
Lead Free Status / Rohs Status
Lead free / RoHS Compliant
PIN FUNCTION DESCRIPTION
Figure 26. Standby Reference Current
, AMBIENT TEMPERATURE (°C)
This pin is the positive supply of the IC. The operating voltage range after startup is 9.0 to 14.5 V.
The output high state (V
source, it can reduce the effects of switching noise on the control circuitry.
Peak currents up to 750 mA can be sourced or sunk, suitable for driving either MOSFET or Bipolar
transistors. This output pin must be shunted by a Schottky diode, 1N5819 or equivalent.
The ground pin is a single return, typically connected back to the power source; it is used as control and
The foldback function provides overload protection. Feeding the foldback input with a portion of the V
voltage (1.0 V max) establishes on the system control loop a foldback characteristic allowing a smoother
startup and sharper overload protection. Above 1.0 V the foldback input is inactive.
When the overvoltage protection pin receives a voltage greater than 17 V, the device is disabled and
requires a complete restart sequence. The overvoltage level is programmable.
A voltage proportional to the current flowing into the power switch is connected to this input. The PWM latch
uses this information to terminate the conduction of the output buffer when working in a current mode of
operation. A maximum level of 1.0 V allows either current or voltage mode operation.
A voltage delivered by an auxiliary transformer winding provides to the demagnetization pin an indication of
the magnetization state of the flyback transformer. A zero voltage detection corresponds to complete core
saturation. The demagnetization detection ensures a discontinuous mode of operation. This function can be
inhibited by connecting Pin 8 to GND.
The synchronization input pin can be activated with either a negative pulse going from a level between 0.7 V
and 3.7 V to GND or a positive pulse going from a level between 0.7 V and 3.7 V up to a level higher than
3.7 V. The oscillator runs free when Pin 9 is connected to GND.
The normal mode oscillator frequency is programmed by the capacitor C
resistance value. C
A capacitor, resistor or a voltage source connected to this pin limits the switching duty−cycle. This pin can
be used as a voltage mode control input. By connecting Pin 11 to Ground, the MC44603A can be shutdown.
A voltage level applied to the R
turn into the reduced frequency mode of operation (i.e. standby mode). An internal hysteresis comparator
allows to return in the normal mode at a higher output power level.
The error amplifier output is made available for loop compensation.
This is the inverting input of the Error Amplifier. It can be connected to the switching power supply output
through an optical (or other) feedback loop.
The reduced frequency or standby frequency programming is made by the R
requires that 5.0 kW ≤ R
sets the internal reference current. The internal reference current ranges from 100 mA to 500 mA. This
R P Stdby (Pin 12)
, connected between Pin 10 and GND, generates the oscillator sawtooth.
) is set by the voltage applied to this pin. With a separate connection to the power
≤ 25 kW.
pin determines the output power level at which the oscillator will
Figure 27. Current Sense Voltage Threshold
Standby Mode versus Temperature
, AMBIENT TEMPERATURE (°C)
choice together with the R
Pin 12 Clamped
at 1.0 V
= 820 pF
= 10 k
= 12 V