XC9103/XC9104/XC9105
Series
■
OPERATIONAL EXPLANATION
The XC9103/04/05 series are step-up DC/DC converter controller ICs with built-in high speed, low ON resistance drivers.
<Error Amp.>
Error amplifier is designed to monitor the output voltage, comparing the feedback voltage (FB) with the reference voltage
Vref. In response to feedback of a voltage lower than the reference voltage Vref, the output voltage of the error amp.
decreases.
<OSC Generator>
This circuit generates the internal reference clock.
<Ramp Wave Generator>
The ramp wave generator generates a saw-tooth waveform based on outputs from the OSC Generator.
<PWM Comparator>
The PWM comparator compares outputs from the error amp. and saw-tooth waveform. When the voltage from the Error
Amp's output is low, the external switch will be set to ON.
<PWM/PFM Controller>
This circuit generates PFM pulses.
The PWM/PFM automatic switching mode switches between PWM and PFM automatically depending on the load. The
PWM/PFM automatic switching mode is selected when the voltage of the CE pin is less than V
DD
- 1.0V, and the control
switches between PWM and PFM automatically depending on the load. PWM/PFM control turns into PFM control when
threshold voltage becomes lower than voltage of error amps. PWM control mode is selected when the voltage of the CE
pin is more than V
DD
- 0.2V. Noise is easily reduced with PWM control since the switching frequency is fixed. The series is
suitable for noise sensitive portable audio equipment as PWM control can suppress noise during operation and PWM/PFM
switching control can reduce consumption current during light load in stand-by.
<Vref 1 with Soft Start>
The reference voltage, Vref (FB pin voltage)=0.9V, is adjusted and fixed by laser trimming (for output voltage settings,
please refer to the notes on next page). To protect against inrush current, when the power is switched on, and also to
protect against voltage overshoot, soft-start time is set internally to 10ms. It should be noted, however, that this circuit
does not protect the load capacitor (C
L
) from inrush current. With the Vref voltage limited and depending upon the input to
the error amps, the operation maintains a balance between the two inputs of the error amps and controls the EXT pin's ON
time so that it doesn't increase more than is necessary.
<Enable Function>
This function controls the operation and shutdown of the IC. When the voltage of the CE pin is 0.2V or less, the mode will
be disable, the channel's operations will stop and the EXT1 pin will be kept at a low level (the external N-type MOSFET will
be OFF). When the IC is in a state of disable, current consumption will be no more than 1.0μA.
When the CE pin's voltage is 0.65V or more, the mode will be enabled and operations will recommence.
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TOREX [ TOREX SEMICONDUCTOR ]
