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부품번호 | MAX4193MJA 기능 |
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기능 | CMOS Micropower Step-Up Switching Regulator | ||
제조업체 | Maxim Integrated | ||
로고 | |||
전체 14 페이지수
19-0915; Rev 2; 9/08
CMOS Micropower Step-Up
Switching Regulator
General Description
Maxim’s MAX630 and MAX4193 CMOS DC-DC regula-
tors are designed for simple, efficient, minimum-size
DC-DC converter circuits in the 5mW to 5W range. The
MAX630 and MAX4193 provide all control and power
handling functions in a compact 8-pin package: a
1.31V bandgap reference, an oscillator, a voltage com-
parator, and a 375mA N-channel output MOSFET. A
comparator is also provided for low-battery detection.
Operating current is only 70µA and is nearly indepen-
dent of output switch current or duty cycle. A logic-level
input shuts down the regulator to less than 1µA quies-
cent current. Low-current operation ensures high effi-
ciency even in low-power battery-operated systems.
The MAX630 and MAX4193 are compatible with most
battery voltages, operating from 2.0V to 16.5V.
The devices are pin compatible with the Raytheon bipo-
lar circuits, RC4191/2/3, while providing significantly
improved efficiency and low-voltage operation. Maxim
also manufactures the MAX631, MAX632, and MAX633
DC-DC converters, which reduce the external compo-
nent count in fixed-output 5V, 12V, and 15V circuits.
See Table 2 at the end of this data sheet for a summary
of other Maxim DC-DC converters.
Applications
+5V to +15V DC-DC Converters
High-Efficiency Battery-Powered DC-DC
Converters
+3V to +5V DC-DC Converters
9V Battery Life Extension
Uninterruptible 5V Power Supplies
5mW to 5W Switch-Mode Power Supplies
Typical Operating Circuit
+5V IN
470μH
6
IC
8 LBD
5
+VS
LX 3
1 LBR
CX
2
MAX630
47pF
VFB 7
GND
4
+5 TO +15V CONVERTER
+15V
OUT
Features
♦ High Efficiency—85% (typ)
♦ 70µA Typical Operating Current
♦ 1µA Maximum Quiescent Current
♦ 2.0V to 16.5V Operation
♦ 525mA (Peak) Onboard Drive Capability
♦ ±1.5% Output Voltage Accuracy (MAX630)
♦ Low-Battery Detector
♦ Compact 8-Pin Mini-DIP and SO Packages
♦ Pin Compatible with RC4191/2/3
Ordering Information
PART
TEMP RANGE
PIN-
PACKAGE
MAX630CPA
0°C to +70°C
8 PDIP
MAX630CSA
0°C to +70°C
8 SO
MAX630CJA
0°C to +70°C
8 CERDIP
MAX630EPA
-40°C to +85°C
8 PDIP
MAX630ESA
-40°C to +85°C
8 SO
MAX630EJA
-40°C to +85°C
8 CERDIP
MAX630MJA
-55°C to +125°C
8 CERDIP**
MAX630MSA/PR
-55°C to +125°C
8 SO†
MAX630MSA/PR-T -55°C to +125°C
8 SO†
MAX4193C/D
0°C to +70°C
Dice*
MAX4193CPA
0°C to +70°C
8 PDIP
MAX4193CSA
0°C to +70°C
8 SO
MAX4193CJA
0°C to +70°C
8 CERDIP
MAX4193EPA
-40°C to +85°C
8 PDIP
MAX4193ESA
-40°C to +85°C
8 SO
MAX4193EJA
-40°C to +85°C
8 CERDIP
MAX4193MJA
-55°C to +125°C
8 CERDIP**
*Dice are specified at TA = +25°C. Contact factory for dice
specifications.
**Contact factory for availability and processing to MIL-STD-883.
†Contact factory for availibility.
Pin Configuration
TOP VIEW
LBR 1
CX 2
LX 3
GND 4
MAX630
MAX4193
8 LBD
7 VFB
6 IC
5 +VS
________________________________________________________________ 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.
CMOS Micropower Step-Up
Switching Regulator
Pin Description
PIN NAME
FUNCTION
1
LBR
Low-Battery Detection Comparator Input. The LBD output, pin 8, sinks current whenever this pin is
below the low-battery detector threshold, typically 1.31V.
2
CX
An external capacitor connected between this terminal and ground sets the oscillator frequency.
47pF = 40 kHz.
3
LX
This pin drives the external inductor. The internal N-channel MOSFET that drives LX has an output
resistance of 4Ω and a peak current rating of 525mA.
4
GND
Ground
5 +VS The positive supply voltage, from 2.0V to 16.5V (MAX630).
The MAX630/MAX4193 shut down when this pin is left floating or is driven below 0.2V. For normal
6 IC operation, connect IC directly to +VS or drive it high with either a CMOS gate or pullup resistor
connected to +VS. The supply current is typically 10nA in the shutdown mode
The output voltage is set by an external resistive divider connected from the converter output to VFB
7 VFB and ground. The MAX630/MAX4193 pulse the LX output whenever the voltage at this terminal is less
than 1.31V.
8
LBD
The Low-Battery Detector output is an open-drain N-channel MOSFET that sinks up to 600μA (typ)
whenever the LBR input, pin 1, is below 1.31V.
Detailed Description
The operation of the MAX630 can best be understood
by examining the voltage regulating loop of Figure 1.
R1 and R2 divide the output voltage, which is com-
pared with the 1.3V internal reference by comparator
COMP1. When the output voltage is lower than desired,
the comparator output goes high and the oscillator out-
put pulses are passed through the NOR gate latch,
turning on the output N-channel MOSFET at pin 3, LX.
As long as the output voltage is less than the desired
voltage, pin 3 drives the inductor with a series of pulses
at the oscillator frequency.
Each time the output N-channel MOSFET is turned on,
the current through the external coil, L1, increases,
storing energy in the coil. Each time the output turns off,
the voltage across the coil reverses sign and the volt-
age at LX rises until the catch diode, D1, is forward
biased, delivering power to the output.
When the output voltage reaches the desired level,
1.31V x (1 + R1 / R2), the comparator output goes low
and the inductor is no longer pulsed. Current is then
supplied by the filter capacitor, C1, until the output volt-
age drops below the threshold, and once again LX is
switched on, repeating the cycle. The average duty
cycle at LX is directly proportional to the output current.
Output Driver (LX Pin)
The MAX630/MAX4193 output device is a large
N-channel MOSFET with an on-resistance of 4Ω and a
peak current rating of 525mA. One well-known advan-
tage that MOSFETs have over bipolar transistors in
switching applications is higher speed, which reduces
switching losses and allows the use of smaller, lighter,
less costly magnetic components. Also important is that
MOSFETs, unlike bipolar transistors, do not require
base current that, in low-power DC-DC converters,
often accounts for a major portion of input power.
The operating current of the MAX630 and MAX4193
increases by approximately 1µA/kHz at maximum
power output due to the charging current required by
the gate capacitance of the LX output driver (e.g., 40µA
increase at a 40kHz operating frequency). In compari-
son, equivalent bipolar circuits typically drive their NPN
LX output device with 2mA of base drive, causing the
bipolar circuit’s operating current to increase by a fac-
tor of 10 between no load and full load.
Oscillator
The oscillator frequency is set by a single external, low-
cost ceramic capacitor connected to pin 2, CX. 47pF
sets the oscillator to 40kHz, a reasonable compromise
between lower switching losses at low frequencies and
reduced inductor size at higher frequencies.
4 _______________________________________________________________________________________
4페이지 CMOS Micropower Step-Up
Switching Regulator
Potted Toroidal Inductors
A typical 1mH, 0.82Ω potted toroidal inductor (Dale TE-
3Q4TA) is 0.685in in diameter by 0.385in high and
mounts directly onto a PC board by its leads. Such
devices offer high efficiency and mounting ease, but at
a somewhat higher cost than molded inductors.
Ferrite Cores (Pot Cores)
Pot cores are very popular as switch-mode inductors
since they offer high performance and ease of design.
The coils are generally wound on a plastic bobbin,
which is then placed between two pot core sections. A
simple clip to hold the core sections together com-
pletes the inductor. Smaller pot cores mount directly
onto PC boards through the bobbin terminals. Cores
come in a wide variety of sizes, often with the center
posts ground down to provide an air gap. The gap pre-
vents saturation while accurately defining the induc-
tance per turn squared.
Pot cores are suitable for all DC-DC converters, but are
usually used in the higher power applications. They are
also useful for experimentation since it is easy to wind
coils onto the plastic bobbins.
Toroidal Cores
In volume production, the toroidal core offers high per-
formance, low size and weight, and low cost. They are,
however, slightly more difficult for prototyping, in that
manually winding turns onto a toroid is more tedious
than on the plastic bobbins used with pot cores.
Toroids are more efficient for a given size since the flux
is more evenly distributed than in a pot core, where the
effective core area differs between the post, side, top,
and bottom.
Since it is difficult to gap a toroid, manufacturers produce
toroids using a mixture of ferromagnetic powder (typically
iron or Mo-Permalloy powder) and a binder. The perme-
ability is controlled by varying the amount of binder,
which changes the effective gap between the ferromag-
netic particles. Mo-Permalloy powder (MPP) cores have
lower losses and are recommended for the highest effi-
ciency, while iron powder cores are lower cost.
Diodes
In most MAX630 circuits, the inductor current returns to
zero before LX turns on for the next output pulse. This
allows the use of slow turn-off diodes. On the other
hand, the diode current abruptly goes from zero to full
peak current each time LX switches off (Figure 1, D1).
To avoid excessive losses, the diode must therefore
have a fast turn-on time.
For low-power circuits with peak currents less than
100mA, signal diodes such as 1N4148s perform well.
For higher-current circuits, or for maximum efficiency at
low power, the 1N5817 series of Schottky diodes are
recommended. Although 1N4001s and other general-
purpose rectifiers are rated for high currents, they are
unacceptable because their slow turn-on time results in
excessive losses.
Table 1. Coil and Core Manufacturers
MANUFACTURER
MOLDED INDUCTORS
Dale
Nytronics
TRW
POTTED TOROIDAL INDUCTORS
Dale
TRW
Torotel Prod.
FERRITE CORES AND TOROIDS
Allen Bradley
Siemens
Magnetics
Stackpole
Magnetics
TYPICAL PART NUMBER
IHA-104
WEE-470
LL-500
TE-3Q4TA
MH-1
PT 53-18
T0451S100A
B64290-K38-X38
555130
57-3215
G-41408-25
DESCRIPTION
500µH, 0.5Ω
470µH, 10Ω
500µH, 0.75Ω
1mH, 0.82Ω
600µH, 1.9Ω
500µH, 5Ω
Tor. core, 500nH/T2
Tor. core, 4µH/T2
Tor. core, 53nH/T2
Pot core, 14mm x 18mm
Pot core, 14 x 8, 250nH/T2
Note: This list does not constitute an endorsement by Maxim Integrated Products and is not intended to be a comprehensive list of
all manufacturers of these components.
_______________________________________________________________________________________ 7
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MAX4193MJA | CMOS Micropower Step-Up Switching Regulator | Maxim Integrated |
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