MB39C007 Datasheet, PDF (7/52 Pages) Fujitsu Component Limited. – 2 ch DC/DC Converter IC Built-in Switching FET & voltage detection function, PFM/PWM Synchronous Rectification, and Down Conversion Support

MB39C007
■ FUNCTION OF EACH BLOCK
• PFM/PWM Logic control circuit
In normal operation, frequency (2.0 MHz) which is set by the built-in oscillator (square wave oscillation circuit)
controls the built-in P-ch MOS FET and N-ch MOS FET for the synchronous rectification operation. In the light
load mode, the intermittent (PFM) operation is executed.
This circuit protects against pass-through current caused by synchronous rectification and against reverse
current caused in a non-successive operation mode.
• 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 PFM/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 VDET pin voltage. 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
VUVLO
CTLP
VDET
VTHHPR
VTHLPR
XPOR
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 PFM/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.
DS04-27246-2E
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