Rainbow Electronics MAX17497B - Manual

MAX17497A/MAX17497B
AC/DC and DC/DC Peak-Current-Mode Converters
with Integrated Step-Down Regulator
 Maxim Integrated Products 1
19-XXXX; Rev 0; 9/11
Ordering Information appears at end of data sheet.
For related parts and recommended products to use with this part,
refer to
www.maxim-ic.com/MAX17497A.related .
General Description
The MAX17497A/MAX17497B devices include both a
current-mode fixed-frequency PWM converter and a syn-
chronous step-down regulator. They contain all the control
circuitry required to design wide-input-voltage noniso-
lated power supplies to supply multiple output rails for
smart meters, industrial control, and other similar applica-
tions. The MAX17497A has its rising/falling undervoltage
lockout (UVLO) thresholds optimized for universal offline
(85V AC to 265V AC) applications, while the MAX17497B
supports undervoltage lockout (UVLO) thresholds suit-
able to low-voltage DC-DC applications. Both devices
also include a 3.3V fixed-output synchronous step-down
regulator that delivers up to 600mA load current.
The switching frequency of the MAX17497A flyback con-
verter is 250kHz, while that of the MAX17497B flyback/
boost converter is 500kHz. The internally compensated
synchronous step-down regulator switches at 1MHz on
both versions. These frequencies allow the use of tiny
magnetic and filter components resulting in compact,
cost-effective power supplies. An EN/UVLO input allows
the user to start the power supply precisely at the desired
input voltage, while also functioning as an on/off pin. The
OVI pin enables implementation of an input overvoltage-
protection scheme that ensures the converter shuts
down when the DC input voltage exceeds the desired
maximum value.
Programmable current limit allows proper sizing and
protection of the primary switching FET. The MAX17497B
supports a maximum duty cycle of 93% and provides
programmable slope compensation to allow optimization
of control loop performance. The MAX17497A supports
a maximum duty cycle of 49%, and has a fixed internal
slope compensation for optimum control loop perfor-
mance. The devices provide an open-drain RESETN pin
that serves as a power-good indicator and enters the
high-impedance state to indicate that the flyback/boost
converter and 3.3V step-down regulator outputs are in
regulation. An SSF pin allows programmable soft-start
time for the flyback/boost converter, while an internal
digital soft-start is employed for the 3.3V step-down regu-
lator to limit inrush current. Hiccup mode overcurrent pro-
tection and thermal shutdown are provided to minimize
dissipation under overcurrent and overtemperature fault
conditions. The devices are available in a space-saving
16-pin (3mm x 3mm) TQFN package with 0.5mm lead
spacing.
Benefits and Features
S Reduced Component Count and Board Space
 Flyback/Boost with Integrated Internally
Compensated Step-Down Regulator
 No Current-Sense Resistor
 Space-Saving 16-Pin (3mm x 3mm) TQFN
Package
S Minimal Radio Interference
 250kHz Switching in Offline Version
Minimizes Interference with Radio Receivers
in Smart Meter Applications
S
Reduced Inrush Current
 Programmable Flyback/Boost Soft-Start
 Internal Digital Soft-Start for Step-Down
Regulator
S Reduced Power Dissipation Under Fault
 Hiccup Mode Overcurrent Protection
 Thermal Shutdown with Hysteresis
S
Robust Protection Features
 Flyback/Boost Programmable Current Limit
 Input Overvoltage Protection
S Optimized Loop Performance
 Programmable Slope Compensation for
Flyback/Boost Maximizes Obtainable Phase
Margin
S High Efficiency
 150mI, 65V-Rated n-MOSFET Offers Typical
Flyback Converter Efficiency Greater Than
80%
 3.3V Step-Down Regulator Efficiency Greater
Than 90%
S Optional Spread Spectrum
Applications
AC/DC Power Supplies for Smart Meter
Applications
Universal-Input Offline AC-DC Power Supplies
Wide-Range DC Input Flyback/Boost Industrial
Power Supplies
E V A L U A T I O N K I T A V A I L A B L E
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
PRELIMINARY