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PDF MAX17497B Data sheet ( Hoja de datos )
| Número de pieza | MAX17497B | |
| Descripción | (MAX17497A/B) AC-DC and DC-DC Peak-Current-Mode Converters | |
| Fabricantes | Maxim Integrated Products | |
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EVALUATION KIT AVAILABLE
MAX17497A/MAX17497B
AC-DC and DC-DC Peak Current-Mode Converters
with Integrated Step-Down Regulator
General Description
The MAX17497A/MAX17497B include both a current-
mode fixed-frequency flyback converter and a synchro-
nous 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
converter is 250kHz, while 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 devices
support a maximum duty cycle greater than 92% and
provides programmable slope compensation to allow
optimization of control-loop performance. 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 fly-
back/boost converter, while an internal digital soft-start is
employed for the 3.3V step-down regulator to limit inrush
current. Hiccup mode overcurrent protection 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
nLMowOSRFDESTON, 150mI, 65V-Rated Internal
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
Ordering Information appears at end of data sheet.
For related parts and recommended products to use with this part,
refer to www.maximintegrated.com/MAX17497A.related.
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
19-5981; Rev 3; 4/13
1 page  
MAX17497A/MAX17497B
AC-DC and DC-DC Peak Current-Mode Converters
with Integrated Step-Down Regulator
ELECTRICAL CHARACTERISTICS (continued)
(VIN = +15V, VEN/UVLO = +2V, COMPF = open, CIN = 1FF, CVCC = 1FF, TA = TJ = -40NC to +125NC, unless otherwise noted. Typical
values are at TA = +25NC.) (Note 1)
PARAMETER
RESETN Higher Thresholds
RESETN Lower Thresholds
EAFN rising
OUTB rising
EAFN falling
OUTB falling
CONDITIONS
MIN
93.5
93.5
90.5
90.5
TYP
95
95
92
92
MAX
96.5
96.5
93.5
93.5
UNITS
%
%
RESETN Delay After EAFN and
VOUTB Reach 95% Regulation
(MAX17497A/MAX17497B)
4 ms
THERMAL SHUTDOWN
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
Temperature rising
160 NC
20 NC
Note 1: All devices are 100% production tested at TA = +25NC. Limits over temperature are guaranteed by design.
Note 2: The MAX17497A is intended for use in universal input power supplies. The internal clamp circuit at IN is used to prevent
the bootstrap capacitor from charging to a voltage beyond the absolute maximum rating of the device when EN/UVLO is
low (shutdown mode). Externally limit the current to IN (hence to clamp) to 2mA (max) when EN/UVLO is low.
Note 3: Guarantees cross conduction is avoided and it is not larger than specified max value to guarantee loop-regulation capability.
Typical Operating Characteristics
(VIN = +15V, VEN/UVLO = +2V, COMPF = open, CIN = 1FF, CVCC = 1FF, TA = TJ = -40NC to +125NC, unless otherwise noted. Typical
values are at TA = +25NC.)
BOOTSTRAP UVLO WAKE-UP LEVEL
vs. TEMPERATURE (MAX17497A)
20.26
MAX17497A/B toc01
IN UVLO WAKE-UP LEVEL
vs. TEMPERATURE (MAX17497B)
4.15
MAX17497A/B toc02
IN UVLO SHUTDOWN LEVEL vs. TEMPERATURE
(MAX17497A /MAX17497B)
4.015
MAX17497A/B toc03
20.24 4.10 4.010
4.005
20.22 4.05 4.000
20.20
3.995
20.18 4.00 3.990
3.985
20.16 3.95 3.980
20.14
-40 -20
0 20 40 60 80 100 120
TEMPERATURE (°C)
3.90
-40 -20
0 20 40 60 80 100 120
TEMPERATURE (°C)
3.975
-40 -20
0 20 40 60 80 100 120
TEMPERATURE (°C)
Maxim Integrated
5
5 Page 
MAX17497A/MAX17497B
AC-DC and DC-DC Peak Current-Mode Converters
with Integrated Step-Down Regulator
Pin Description (continued)
PIN NAME
FUNCTION
8
SSF
Soft-Start Pin for Flyback/Boost Converter. Connect a capacitor from SSF to SGND to set the
soft-start time interval.
9
OUTB
Feedback for Step-Down Regulator. Connects OUTB to the positive terminal of the step-down
regulator output capacitor.
10
PGNDB
Power Ground for Step-Down Regulator
11
LXB
External Inductor Connection for Step-Down Regulator. Connect to one end of the output inductor.
Connect the other end of output inductor to output capacitor.
Internal Step-Down Regulator Input. Connect INB to either VOUTF, the output of flyback/boost
12 INB converter, or directly to the DC input source, as needed in the application. Bypass INB to PGNDB
with a 2.2FF minimum ceramic capacitor.
13
RESETN
Open-Drain Output. RESETN goes high when both the outputs are within 5% of their regulation point.
RESETN goes low when either of the outputs falls below 92% of their regulation value.
14
PGNDF
Power Ground for Flyback/Boost Converter
15 LXF External Transformer/Inductor Connection for Flyback/Boost Converter
16
IN
Internal Linear Regulator Input. Connect IN to the input-voltage source. Bypass IN to PGNDF with
ceramic capacitor of at least 1FF.
—
EP
Exposed Pad. Internally connected to SGND. Connect EP to a large copper plane at SGND potential
to provide adequate thermal dissipation. Connect EP (SGND) to PGNDF at a single point.
Detailed Description
The MAX17497A is optimized for implementing a noniso-
lated offline flyback converter with output power of up to
30W and a 3.3V, 600mA power rail using the on-board
synchronous step-down regulator. The output voltage of
the flyback converter serves as the input supply voltage
to the on-board 3.3V integrated synchronous step-down
regulator. The outputs of the flyback converter and step-
down regulator are regulated with independent feedback
loops, thus providing two accurately controlled voltages
for the system. If needed, more semi-regulated outputs
can be generated using additional secondary windings
on the flyback converter transformer. The MAX17497B is
optimized for implementing a nonisolated flyback/boost
converter up to 15W and a 3.3V, 600mA synchronous
step-down regulator in low-voltage DC-DC applications
down to 4.5V DC. See the Figure 1 for more information.
Input Voltage Range
The MAX17497A has different rising and falling UVLO
thresholds on the IN pin than those of the MAX17497B.
The thresholds for the MAX17497A are optimized for
implementing power-supply startup schemes typically
used for offline AC-DC power supplies. The MAX17497A
is therefore well suited for operation from the recti-
fied DC bus in AC-DC power-supply applications typi-
cally encountered in electric metering and other low-
power industrial power-supply applications. As such,
the MAX17497A has no limitation on the maximum
input voltage as long as the external components are
rated suitably and the maximum operating voltages of
the MAX17497A are respected. The MAX17497A can
successfully be used in universal input rectified (85V to
265V AC) bus applications, rectified 3-phase DC bus
applications, and telecom (36V to 72V DC) applications.
Maxim Integrated
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet MAX17497B.PDF ] | |
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