MB39C011APFT-G-BND-ERE1 Datasheet, PDF (12/53 Pages) Cypress Semiconductor – 2 ch DC/DC Converter IC with Synchronous Rectification

MB39C011A
8. Functional Description
8.1 DC/DC Converter Block
8.1.1 Triangular Wave Oscillator Block (OSC)
The triangular wave oscillator block has a built-in capacitor for setting the oscillator frequency. The triangular wave is
generated by connecting a resistor for selecting the frequency of the triangular wave to the RT pin (pin 5).The triangular
wave is input internally to the PWM comparator in the IC.
8.1.2 Error Amplifier Block (Error Amp1, Error Amp2)
The error amplifiers (Error Amp1, Error Amp2) detect the DC/DC converter output voltages and output the PWM control
signals. The output voltages can be set to an arbitrary level by externally connecting output voltage setting resistors to the
error amplifier inverted input pins.
In addition, an arbitrary loop gain can be set by connecting a feedback resistor and capacitor from the error amplifier output
(FB1 pin (pin 6), FB2 pin (pin 11)) to inverted input terminal (-INE1 pin (pin 7), -INE2 pin (pin 10)), enabling stable phase
compensation of the system.Connecting a soft-start capacitor to the CSCP1 and CSCP2 pins (pins 8 and 9) prevents rush
currents when the IC is turned on. Using an error amplifier for soft-start detection makes the soft-start time constant,
independent of the output load of DC/DC converter.
8.1.3 PWM Comparator Block (PWM Comp.)
The PWM comparator circuit is a voltage-pulse width converter for controlling the output duty of the error amplifiers (Error
Amp1, Error Amp2) depending on their output voltage.
The PWM comparator circuit compares the triangular wave generated by the triangular wave oscillator to the error amplifier
output voltage and turns on the external output transistor during the interval in which the triangular wave voltage is lower
than the error amplifier output voltage.
8.1.4 Output Block (Drive1-1, 1-2, Drive 2-1, 2-2)
The output circuit consists of CMOS drivers on both the high side and the low side, and is capable of driving an external
P-ch MOS FET on the high side and an external N-ch MOS FET on the low side.
8.1.5 Power Supply Control Block (CTL)
The DC/DC converter can be put into standby mode by setting the CTL pin (pin 13) to the “L” level (the maximum power
supply current in standby mode is 10 A), and put into operating mode by setting the CTL pin (pin 13) to the “H” level.
Control Function Table
CTL
IC
L
OFF (Standby)
H
ON (Operating)
Document Number: 002-08369 Rev. *A
Page 12 of 53