SC1175
POWER MANAGEMENT
Block Diagram
NOTES
(1) Block 1 (top) is the Master and Block 2 (bottom) is the Slave in current sharing configuration.
(2) For independant operation there is no Master or Slave.
Applications Information
Theory of Operation
Main Loop(s)
output. In this mode, the positive input of error
amplifier 2 is connected externally to Vref. If the
application uses a common input voltage, the
sawtooth phase shift between the channels
provides some measure of input ripple current
cancellation.
The SC1175 is a dual, voltage mode synchronous
Buck controller, the two separate channels are
identical and share only IC supply pins (Vcc and
GND), output driver ground (PGND) and pre-driver
supply voltage (BSTC). They also share a common
oscillator generating a sawtooth waveform for chan-
nel 1 and an inverted sawtooth for channel 2. Each
channel has its own current limit comparator. Chan-
nel 1 has the positive input of the error amplifier
internally connected to Vref. Channel 2 has both
inputs of the error amplifier uncommitted and avail-
able externally. This allows the SC1175 to operate in
two distinct modes.
b) Two channels operating in current sharing
mode with common output voltage and either
common input voltage or different input voltages.
In this mode, channel 1 operates as a voltage
mode Buck controller, as before, but error amp 2
monitors and amplifies the difference in voltage
across the output current sense resistors of
channel 1 and channel 2 (Master and Slave) and
adjusts the Slave duty cycle to match output
currents. Because of finite gain and offsets in the
loop, the resistor ratio for perfect current match-
a) Two independent channels with either com-
mon or different input voltages and different
output voltages. The two channels each have
their own voltage feedback path from their own
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