参数资料
型号: MAX1700
厂商: Maxim Integrated Products, Inc.
元件分类: DC/DC变换器
英文描述: 1-Cell to 3-Cell, High-Power 1A, Low-Noise, Step-Up DC-DC Converters
中文描述: 1节至3节电池、大功率(1A)、低噪声、升压型DC-DC转换器
文件页数: 13/16页
文件大小: 248K
代理商: MAX1700
Referenc e
The MAX1700/MAX1701 have an internal 1.250V, 1%
bandgap reference. Connect a 0.22μF bypass capaci-
tor to GND within 0.2in. (5mm) of the REF pin. REF can
source up to 50μA of external load current.
Power-OK (MAX 1701)
The MAX1701 features a power-good comparator. This
comparator’s open-drain output (POK) is pulled low
when the output voltage falls to 10% below the regula-
tion point.
Gain Bloc k (MAX 1701)
The MAX1701’s gain block can function as a third com-
parator or can be used to build a linear regulator using
an external P-channel MOSFET pass device. The gain-
block output is a single-stage transconductance ampli-
fier that drives an open-drain N-channel MOSFET.
Figure 9 shows the gain block used in a linear regula-
tor. The output of an external P-channel pass element is
compared to the internal reference. The difference is
amplified and used to drive the gate of the pass ele-
ment. Use a logic-level PFET such as the Fairchild
NDS336P (R
DS(ON)
= 270m
). If the PFET R
DS(ON)
is
less than 250m
, the linear regulator output filter
capacitance may need to be increased to above 47μF.
__________________Design Proc edure
S etting the Output V oltages
Set the output voltage between 2.5V and 5.5V by con-
necting a resistor voltage-divider to FB from OUT to
GND, as shown in Figure 2. The resistor values are then
as follows:
R1 = R2 (V
OUT
/V
FB
- 1)
where V
FB
, the boost-regulator feedback setpoint, is
1.23V. Since the input bias current into FB is less than
20nA, R2 can have a large value (such as 270k
or
less) without sacrificing accuracy. Connect the resistor
voltage-divider as close to the IC as possible, within
0.2in. (5mm) of the FB pin.
Induc tor S elec tion
The MAX1700/MAX1701’s high switching frequency
allows the use of a small surface-mount inductor. A
10μH inductor should have a saturation-current rating
that exceeds the N-channel switch current limit of 1.6A.
However, it is generally acceptable to bias the inductor
current into saturation by as much as 20%, although
this will slightly reduce efficiency. For high efficiency,
choose an inductor with a high-frequency core material
(such as ferrite) to reduce core losses. To minimize
radiated noise, use a toroid, pot core, or shielded bob-
bin inductor. Connect the inductor from the battery to
the LX pin as close to the IC as possible. See Table 4
for a list of component suppliers and Table 5 for sug-
gested components.
M
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, S tep-Up DC-DC Converters
______________________________________________________________________________________
13
AIN
AO
N
LX
P
IN
REF
R6
R5
2x
100
μ
F
47
μ
F
MAX1701
20k
Figure 9. Using Gain Block as a Linear Regulator
PRODUCTION
INDUCTORS
CAPACITORS
DIODES
Surface Mount
Sumida CDR63B, CD73, CDR73B, CD74B series
Coilcraft DO1608, DO3308, DT3316 series
Matsuo 267 series
Sprague 595D series
AVX TPS series
Sanyo OS-CON series
Nichicon PL series
Motorola MBR0520L
Through Hole
Sumida RCH654 series
1N5817
Table 5. Component Selection Guide
(847) 956-0702
81-3-3607-5144
USA: (847) 956-0666
J apan: 81-3-3607-5111
Sumida
(619) 661-1055
81-7-2070-1174
USA: (619) 661-6835
J apan: 81-7-2070-6306
Sanyo
(602) 994-6430
USA: (602) 303-5454
Motorola
(714) 960-6492
USA: (714) 969-2491
Matsuo
(847) 639-1469
USA: (847) 639-6400
Coilcraft
(803) 626-3123
USA: (803) 946-0690
(800) 282-4975
AVX
FAX
PHONE
SUPPLIER
Table 4. Component Suppliers
相关PDF资料
PDF描述
MAX1700-MAX1701 1-Cell to 3-Cell, High-Power 1A, Low-Noise, Step-Up DC-DC Converters
MAX1700EEE 1-Cell to 3-Cell, High-Power 1A, Low-Noise, Step-Up DC-DC Converters
MAX1701EEE 18-Bit Universal Bus Transceivers With 3-State Outputs 56-SSOP -40 to 85
MAX1702B Triple-Output Power-Management IC for Microprocessor-Based Systems
MAX1702BEGX Triple-Output Power-Management IC for Microprocessor-Based Systems
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