UC1826
UC2826
UC3826
Secondary Side Average Current Mode Controller
FEATURES
DESCRIPTION
The UC1826 family of average current mode controllers accurately
accomplishes secondary side average current mode control. The sec-
ondary side output voltage is regulated by sensing the output voltage
and differentially sensing the AC switching current. The sensed output
voltage drives a voltage error amplifier.The AC switching current, mon-
itored by a current sense resistor, drives a high bandwidth, low offset
current error amplifier. The output of the voltage error amplifier can be
used to drive the current amplifier which filters the measured inductor
current. Fast transient response is accomplished by utilizing voltage
feedforward in generating the PWM ramp.
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Practical Secondary Side Control of
Isolated Power Supplies
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1MHz Operation
Tailored Loop Bandwidth Provides
Excellent Noise Immunity
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Voltage Feedforward Provides
Superior Transient Response
Accurate Programmable Maximum
Duty Cycle
The UC1826 features load share, oscillator synchronization, undervolt-
age lockout, and programmable output control. Multiple chip operation
can be achieved by connecting up to ten UC1826 chips in parallel.The
SHARE bus and CLKSYN bus provide load sharing and synchroniza-
tion to the fastest oscillator respectively.With its tailored bandwidth, the
UC1826 provides excellent noise immunity and is an ideal controller to
achieve high power, secondary side average current mode control.
Multiple Chips Can be Synchronized
to Fastest Oscillator
Wide Gain Bandwidth Product
(70MHz, Acl>10) Current Error
Amplifier
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Up to Ten Devices Can Easily Share
a Common Load
BLOCK DIAGRAM
Pin Numbers refer to 24-pin packages.
UDG-95013
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