MAX1708EEE データシートの表示（PDF） - Maxim Integrated
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MAX1708EEE Datasheet PDF : 13 Pages
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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
VOUT
MAX1708
FB
KEEP SHORT
R4
R3
Figure 3. Simplified PWM Controller Functional Diagram
Figure 4. Adjustable Output Voltage
______________________________________________________________________________________ 11
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