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PDF MAX1708 Data sheet ( Hoja de datos )
| Número de pieza | MAX1708 | |
| Descripción | High-Frequency / High-Power / Low-Noise / Step-Up DC-DC Converter | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MAX1708 (archivo pdf) en la parte inferior de esta página. Total 13 Páginas | ||
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19-2068; Rev 0; 7/01
High-Frequency, High-Power, Low-Noise,
Step-Up DC-DC Converter
General Description
The MAX1708 sets a new standard of space savings for
high-power, step-up DC-DC conversion. It delivers up
to 10W at a fixed (3.3V or 5V) or adjustable (2.5V to
5.5V) output, using an on-chip power MOSFET from a
+0.7V to +5V supply.
Fixed-frequency PWM operation ensures that the
switching noise spectrum is constrained to the 600kHz
fundamental and its harmonics, allowing easy postfilter-
ing for noise reduction. External clock synchronization
capability allows for even tighter noise spectrum con-
trol. Quiescent power consumption is less than 1mW to
extend operating time in battery-powered systems.
Two control inputs (ONA, ONB) allow simple push-on,
push-off control through a single momentary push-but-
ton switch, as well as conventional on/off logic control.
The MAX1708 also features programmable soft-start
and current limit for design flexibility and optimum per-
formance with batteries. The maximum RMS switch cur-
rent rating is 5A. For a device with a higher (10A)
switch current rating, refer to the MAX1709 data sheet.
Features
o On-Chip 5A Power MOSFET
o 5V, 2A Output from a 3.3V Input
o Fixed 3.3V or 5V Output Voltage or
Adjustable (2.5V to 5.5V)
o Input Voltage Range Down to 0.7V
o Low Power Consumption
1mW Quiescent Power
1µA Current in Shutdown Mode
o Low-Noise, Constant Frequency Operation
(600kHz)
o Synchronizable Switching Frequency
(350kHz to 1000kHz)
o Small QSOP Package
________________________Applications
Routers, Servers, Workstations, Card Racks
Local 2.5V to 3.3V or 5V Conversion
Local 3.3V to 5V Conversion
3.6V or 5V RF PAs in Communications Handsets
PART
MAX1708EEE
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
16 QSOP
Typical Operating Circuit
Pin Configuration
INPUT
1V TO 5V
2.2µH
OFF ON
SYNC
OR
INTERNAL
ONA LX
MAX1708
CLK
SS/LIM
GND
REF OUT
OUTPUT
3.3V, 5V,
OR ADJ
UP TO 2A
TOP VIEW
ONB 1
ONA 2
LX 3
LX 4
LX 5
GND 6
SS/LIM 7
REF 8
MAX1708
QSOP
16 CLK
15 3.3/5
14 PGND
13 PGND
12 PGND
11 FB
10 OUT
9 GND
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1 page  
High-Frequency, High-Power, Low-Noise,
Step-Up DC-DC Converter
(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics
EFFICIENCY vs. OUTPUT CURRENT
100
80 VIN = 3.3V
VIN = 2.5V
60
40
20
0
0.1
VOUT = 5V
1 10 100 1000
OUTPUT CURRENT (mA)
10,000
EFFICIENCY vs. OUTPUT CURRENT
100
VIN = 2.5V
80
60
VIN = 1.2V
40
20
VOUT = 3.3V
0
0.1
1 10 100 1000
OUTPUT CURRENT (mA)
10,000
EFFICIENCY vs. SWITCHING FREQUENCY
90
89
88
87
VIN = 3.3V, VOUT = 5V, IOUT =1A
86
350 450 550 650 750 850
SWITCHING FREQUENCY (kHz)
950
LOAD REGULATION
(VIN = 3.3V, VOUT = 5V)
2.0
1.5
1.0
0.5
0
-0.5
-1.0
-1.5
PLOT NORMALIZED TO IOUT = 500mA
-2.0
0.1 1 10 100 1000
OUTPUT CURRENT (mA)
10,000
LINE REGULATION
(VOUT = 3.3V)
0.8
0.7
IOUT = 1A
0.6
0.5
0.4
0.3
0.2
0.1
0
-0.1
-0.2 IOUT = 500mA
-0.3 PLOT NORMALIZED TO VIN = 2.5V
1.50 1.75 2.00 2.25 2.50 2.75
INPUT VOLTAGE (V)
3.00
LOAD REGULATION
(VIN = 2.5V, VOUT = 3.3V)
2.0
1.5
1.0
0.5
0
-0.5
-1.0
-1.5
PLOT NORMALIZED TO IOUT = 500mA
-2.0
0.1 1 10 100 1000
OUTPUT CURRENT (mA)
10,000
NO LOAD INPUT CURRENT
vs. INPUT VOLTAGE
25
20
VOUT = 5V, VIN INCREASING
15
10
VOUT = 3.3V, VIN INCREASING
5
0
0123456
INPUT VOLTAGE (V)
LINE REGULATION
(VOUT = 5V)
0.3
0.2
0.1
0
-0.1
IOUT = 1A
IOUT = 500mA
-0.2
PLOT NORMALIZED TO VIN = 3.3V
-0.3
2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00
INPUT VOLTAGE (V)
NO LOAD INPUT CURRENT
vs. INPUT VOLTAGE
70
60
VOUT = 5V, VIN DECREASING
50
40
30
20
VOUT = 3.3V, VIN DECREASING
10
0
0123456
INPUT VOLTAGE (V)
_______________________________________________________________________________________ 5
5 Page 
High-Frequency, High-Power, Low-Noise,
Step-Up DC-DC Converter
Table 3. Component Selection Guide
PRODUCTION
Surface mount
INDUCTORS
Coiltronics UP2B-2R2
Coilcraft DO3316P-222HC
CAPACITORS
Sanyo 6TPC100M
Panasonic EEFUE0J151R
DIODES
Motorola MBRD1035CTL
Central CMSH5-20
Table 4. Component Suppliers
SUPPLIER
Central
Coilcraft
Coiltronics
Motorola
Panasonic
PHONE
631-435-1110
847-639-6400
561-241-7876
602-303-5454
714-373-7939
FAX
631-435-1824
847-639-1489
561-241-9339
602-994-6430
714-373-7183
__________________Design Procedure
Inductor Selection (L1)
The MAX1708’s high switching frequency allows the
use of a small-size inductor. Use a 2.2µH inductor for
600kHz operation. If the MAX1708 is synchronized at a
different frequency, scale the inductor value with the
inverse of frequency (L1 = 2.2µH ✕ 600kHz / fSYNC).
The PWM design tolerates inductor values within ±25%
of this calculated value, so choose the closest standard
inductor value. For example, use 3.3µH for 350kHz and
1.5µH for 1MHz).
Inductors with a ferrite core or equivalent are recom-
mended; powder iron cores are not recommended for
use at high switching frequencies. Ensure the induc-
tor’s saturation rating (the current at which the core
begins to saturate and inductance falls) exceeds the
internal current limit. Note that this current may be
reduced through SS/LIM if less than the MAX1708’s full
load current is needed (see Electrical Characteristics
for ratings). For highest efficiency, use a coil with low
DC resistance, preferably under 20mΩ. To minimize
radiated noise, use a toroid, pot core, or shielded
inductor. See Tables 3 and 4 for a list of recommended
components and component suppliers. To calculate
the maximum output current (in amperes), use the fol-
lowing equation:
IOUT(MAX)
=
D' ILIM
−
D'
VOUT +
2×
VD −
ƒ × L1
VIN
where:
VIN = input voltage
VD = forward voltage drop of the Schottky diode
at ILIM
VOUT = output voltage
D' = (VIN) / (VOUT + VD), neglecting switch voltage
drop
f = switching frequency
L1 = inductor value
ILIM = minimum value of switch current limit from
Electrical Characteristics or set by R1 of
Figure 1.
FB
REF
SLOPE
COMP
SS/LIM
12.5
(LIMITED TO 100mV)
OSCILLATOR
RQ
S
LX
N
11mΩ
PGND
VIN
LX
MAX1708
FB
KEEP SHORT
R4
R3
VOUT
Figure 3. Simplified PWM Controller Functional Diagram
Figure 4. Adjustable Output Voltage
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet MAX1708.PDF ] | |
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