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PDF MAX17244 Data sheet ( Hoja de datos )
| Número de pieza | MAX17244 | |
| Descripción | Synchronous Buck Converter | |
| Fabricantes | Maxim Integrated | |
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MAX17244
EVALUATION KIT AVAILABLE
3.5V–36V, 2.5A, Synchronous Buck Converter
With 28µA Quiescent Current and Reduced EMI
General Description
The MAX17244 high-efficiency, synchronous step-down
DC-DC converter with integrated MOSFETs operates
over a 3.5V to 36V input voltage range with 42V input
transient protection. The device can operate in dropout
condition by running at 98% duty cycle. This converter
delivers up to 2.5A and generates fixed output voltages of
3.3V/5V, along with the ability to program the output
voltage between 1V to 10V.
The MAX17244 uses a current-mode control architecture.
The device can operate in the pulse-width modulation
(PWM) or pulse-frequency modulation (PFM) control
schemes. PWM operation provides constant frequency
operation at all loads, and is useful in applications sensitive
to switching frequency. PFM operation disables negative
inductor current and additionally skips pulses at light
loads for high efficiency. Under light-load applications,
the external sync pin FSYNC logic input allows the
device to operate either in PFM mode for reduced current
consumption or fixed-frequency FPWM (forced-PWM)
mode to eliminate frequency variation to minimize EMI.
Fixed-frequency FPWM mode is extremely useful for
power supplies designed for RF transceivers where tight
emission control is necessary.
This device is available in a compact 16-pin (5mm x 5mm)
TQFN package with exposed pad and 16-pin TSSOP.
-40°C to +85°C operation.
Applications
●● Distributed Supply Regulation
●● Wall Transformer Regulation
●● General-Purpose Point-of-Load
Benefits and Features
●● Eliminates External Components and Reduces
Total Cost
• Integrated High-Side and Low-Side Switch Enables
Synchronous Operation for High Efficiency and
Reduced Cost
• All-Ceramic Capacitor Solution Allows Ultra-
Compact Solution Size
• 220kHz to 2.2MHz Adjustable Frequency with
External Synchronization
• Power Good Output and High-Voltage EN Input
Simplify Power Sequencing
●● Increases Design Flexibility
• 180° Out-of-Phase Clock Output at SYNCOUT
Enables Cascaded Power Supplies for Increased
Power Output
• Fixed Output Voltage with ±2% Accuracy (5V/3.3V)
or Externally Resistor Adjustable (1V to 10V)
●● Reduces Power Dissipation
• >90% Peak Efficiency
• PWM and PFM Operation Optimizes Conversion
Efficiency From Heavy to Light Loads
• Automatic LX Slew-Rate Adjustment for Optimum
Efficiency Across Operating Frequency Range
• Low 5μA (typ.) Shutdown Current
• Low 28μA (typ.) Quiescent Current
●● Operates Reliably
• 42V Input Voltage Transient Protection
• Fixed 8ms Internal Software Start Reduces Input
Inrush Current
• Cycle-by-Cycle Current Limit, Thermal Shutdown
with Automatic Recovery
• Reduced EMI Emission with Spread-Spectrum
Control
Ordering Information and Typical Application Circuit
appears at end of data sheet.
19-8526; Rev 0; 4/16
1 page  
MAX17244
3.5V–36V, 2.5A, Synchronous Buck Converter
With 28µA Quiescent Current and Reduced EMI
Electrical Characteristics (continued)
(VSUP = VSUPSW = 14V, VEN = 14V, L1 = 2.2µH, CIN = 4.7µF, COUT = 22µF, CBIAS = 1µF, CBST = 0.1µF, RFOSC = 12kΩ,
TA = TJ = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 3)
PARAMETER
OSCILLATOR FREQUENCY
SYMBOL
Oscillator Frequency
EXTERNAL CLOCK INPUT (FSYNC)
External Input Clock
Acquisition Time
tFSYNC
External Input Clock Frequency
External Input Clock High
Threshold
VFSYNC_HI
External Input Clock Low
Threshold
VFSYNC_LO
Soft-Start Time
ENABLE INPUT (EN)
tSS
Enable Input High Threshold
Enable Input Low Threshold
Enable Threshold-Voltage
Hysteresis
VEN_HI
VEN_LO
VEN_HYS
Enable Input Current
POWER GOOD (PGOOD)
IEN
PGOOD Switching Level
PGOOD Debounce Time
VTH_RISING
VTH_FALLING
PGOOD Output Low Voltage
PGOOD Leakage Current
SYNCOUT Low Voltage
SYNCOUT Leakage Current
FSYNC Leakage Current
OVERVOLTAGE PROTECTION
Overvoltage Protection
Threshold
CONDITIONS
RFOSC = 73.2kΩ
RFOSC = 12kΩ
RFOSC = 12kΩ (Note 6)
VFSYNC rising
VFSYNC falling
TA = +25°C
VFB rising, VPGOOD = high
VFB falling, VPGOOD = low
ISINK = 5mA
VOUT in regulation, TA = +25°C
ISINK = 5mA
TA = +25°C
TA = +25°C
VOUT rising (monitored at FB pin)
VOUT falling (monitored at FB pin)
MIN TYP MAX UNITS
340 400 460 kHz
2.0 2.2 2.4 MHz
1 Cycles
1.8 2.6 MHz
1.4 V
0.4 V
5.6 8 12 ms
2.4
0.6
0.2
0.1 1
V
V
µA
93 95 97
90 92 94 %VFB
10 25 50
µs
0.4 V
1 µA
0.4 V
1 µA
1 µA
105
%
102
Note 3: Limits are 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed by design.
Note 4: Device not in dropout condition.
Note 5: Guaranteed by design; not production tested.
Note 6: FB regulation voltage is 1%, 1.01V (max), for -40°C < TA < +105°C.
Note 7: Contact the factory for SYNC frequency outside the specified range.
www.maximintegrated.com
Maxim Integrated │ 5
5 Page 
MAX17244
3.5V–36V, 2.5A, Synchronous Buck Converter
With 28µA Quiescent Current and Reduced EMI
OUT
COMP
PGOOD
EN
SUP BIAS
FB
FBSW
FBOK
AON HVLDO
SWITCH
OVER
EAMP
REF
SOFT
START
PWM
LOGIC
HSD
CS
BIAS
BST
SUPSW
LX
MAX17244
SLOPE
COMP
LSD
OSC
PGND
SYNCOUT
Figure 1. Internal Block Diagram
FSYNC
FOSC AGND
The input voltage at which the device enters dropout can
be approximated as:
VSUP
=
VOUT
+
(IOUT× R ON_H)
0.98
Note: The equation above does not take into account the
efficiency and switching frequency, but is a good first-order
ainptphreoxEimleacttiroicna.lUCsheatrhaecteRrOisNtic_sHtanbulme.ber from the max column
Linear Regulator Output (BIAS)
The devices include a 5V linear regulator (BIAS) that
provides power to the internal circuit blocks. Connect a
1µF ceramic capacitor from BIAS to AGND. When the
output voltage is set between 3V and 5.5V, the internal
linear regulator only provides power until the output is in
regulation. The internal linear regulator turns off once the
output is in regulation and allows OUT to provide power
to the device. The internal regulator turns back on once
the external load on the output of the device is higher than
100mA. In addition, the linear regulator turns on anytime
the output voltage is outside the 3V to 5.5V range.
Power-Good Output (PGOOD)
The devices feature an open-drain power-good output,
PGOOD. PGOOD asserts when VOUT rises above 95%
of its regulation voltage. PGOOD deasserts when VOUT
drops below 92% of its regulation voltage. Connect
PGOOD to BIAS with a 10kΩ resistor.
Overvoltage Protection (OVP)
If the output voltage reaches the OVP threshold, the high-
side switch is forced off and the low-side switch is forced
on until negative-current limit is reached. After negative-
current limit is reached, both the high-side and low-side
switches are turned off. The MAX17244 offers a lower
voltage threshold for applications requiring tighter limits
of protection.
www.maximintegrated.com
Maxim Integrated │ 11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet MAX17244.PDF ] | |
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