SC1176 查看數據表（PDF） - Semtech Corporation
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SC1176 Datasheet PDF : 23 Pages
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POWER MANAGEMENT
Block Diagram
SC1176/SC1176A
NOTES
(1) Block 1 (top) is the Master and Block 2 (bottom) is the Slave in current sharing configuration.
(2) For independent operation there is no Master or Slave.
Applications Information - Theory of Operation
Main Loop(s)
The SC1176 is a dual, voltage mode synchronous
Buck controller, the two separate channels are identi-
cal 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 channel 1 and an
inverted sawtooth for channel 2. Each channel has its
own current limit comparator. Channel 1 has the
positive input of the error amplifier internally connected
to Vref. Channel 2 has both inputs of the error ampli-
fier uncommitted and available externally. This allows
the SC1176 to operate in two distinct modes.
a) Two independent channels with either com-
mon or different input voltages and different
output voltages. The two channels each have
2006 Semtech Corp.
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their own voltage feedback path from their own
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.
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-
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