MB39C015 Datasheet, PDF (8/43 Pages) Cypress Semiconductor – High efficiency : 96% (Max)

MB39C015
5. Function of Each Block
■ PWM Logic control circuit
The built-in P-ch and N-ch MOS FETs are controlled for synchronization rectification according to the frequency (2.0 MHz) oscillated
from the built-in oscillator (square wave oscillation circuit).
■ IOUT Comparator circuit
This circuit detects the current (ILX) which flows to the external inductor from the built-in P-ch MOS FET. By comparing VIDET obtained
through I-V conversion of peak current IPK of ILX with the Error Amp output, the built-in P-ch MOS FET is turned off via the PWM Logic
Control circuit.
■ Error Amp phase compensation circuit
This circuit compares the output voltage to reference voltages such as VREF. This IC has a built-in phase compensation circuit that
is designed to optimize the operation of this IC.This needs neither to be considered nor addition of a phase compensation circuit and
an external phase compensation device.
■ VREF circuit
A high accuracy reference voltage is generated with BGR (bandgap reference) circuit. The output voltage is 1.30 V (Typ).
■ Voltage Detection (VDET) circuit
The voltage detection circuit monitors the voltage at the VDET pin. Normally, use the XPOR pin through pull-up with an external
resistor. When the VDET pin voltage reaches 0.6 V, it reaches the H level.
Timing chart example : (XPOR pin pulled up to VIN)
VIN
CTLP
VUVLO
VDET
XPOR
VTHHPR
VTHLPR
VUVLO : UVLO threshold voltage
VTHHPR, VTHLPR : XPOR threshold voltage
■ Protection circuit
This IC has a built-in over-temperature protection circuit. The over-temperature protection circuit turns off both N-ch and P-ch switching
FETs when the junction temperature reaches  135 °C . When the junction temperature comes down to  110 °C , the switching FET
is returned to the normal operation. Since the PWM control circuit of this IC is in the control method in current mode, the current peak
value is also monitored and controlled as required.
Document Number: 002-08364 Rev. *A
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