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The MAX8597/MAX8598/MAX8599 voltage-mode PWM
step-down controllers are designed to operate from a
4.5V to 28V input supply and generate output voltages
down to 0.6V. A proprietary switching algorithm stretches
the duty cycle to >99.5% for low-dropout design.
Unlike conventional step-down regulators using a pchannel
high-side MOSFET to achieve high duty cycle,
the MAX8597/MAX8598/MAX8599 drive n-channel
MOSFETs resulting in high efficiency and high-current-capability
designs.
The MAX8597 is available in a 20-pin thin QFN package
and is designed for applications that use an analog
signal to control the output voltage with an adjustable
offset, such as DC fan-speed control. This is achieved
with an internal uncommitted operational amplifier. The
MAX8597 is also targeted for tracking output-voltage
applications for chipsets, ASIC and DSP cores, and I/O
supplies. The MAX8598/MAX8599 are available in a 16-
pin thin QFN package and do not have the uncommitted
operational amplifier, reference input, and reference output,
but offer an open-drain, power-OK output.
The MAX8597/MAX8598/MAX8599 allow startup with
prebias voltage on the output for applications where a
backup supply or a tracking device may charge the
output capacitor before the MAX8597/MAX8598/
MAX8599 are enabled. In addition, the MAX8599 features
output overvoltage protection.
These controllers also feature lossless high-side peak
inductor current sensing, adjustable current limit, and
hiccup-mode short-circuit protection. Switching frequency
is set with an external resistor from 200kHz to
1.4MHz. This wide frequency range combined with a
wide-bandwidth error amplifier enables the loop compensation
scheme to give the user ample flexibility to
optimize for cost, size, and efficiency.
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