MAX1674-MAX1676
更新时间：2024-09-18 02:28:29
品牌：MAXIM
描述：High-Efficiency, Low-Supply-Current, Compact, Step-Up DC-DC Converters
概述
数据手册MAX1674-MAX1676 概述
High-Efficiency, Low-Supply-Current, Compact, Step-Up DC-DC Converters 高效率，低电源电流，紧凑的，升压型DC- DC转换器
MAX1674-MAX1676 数据手册
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PDF下载19-1360; Rev 0; 7/98
Hig h -Effic ie n c y, Lo w -S u p p ly-Cu rre n t ,
Co m p a c t , S t e p -Up DC-DC Co n ve rt e rs
45/MAX176
Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
♦ 94% Efficient at 200mA Output Current
♦ 16µA Quiescent Supply Current
The MAX1674/MAX1675/MAX1676 compact, high-effi-
ciency, step-up DC-DC converters fit in small µMAX
packages. They feature a built-in synchronous rectifier,
which improves efficiency and reduces size and cost
by eliminating the need for an external Schottky diode.
Quiescent supply current is only 16µA.
♦ Internal Synchronous Rectifier (no external diode)
♦ 0.1µA Logic-Controlled Shutdown
The input voltage ranges from 0.7V to V
, where
♦ LBI/LBO Low-Battery Detector
OUT
V
OUT
can be set from 2V to 5.5V. Start-up is guaran-
♦ Selectable Current Limit for Reduced Ripple
♦ Low-Noise, Anti-Ringing Feature (MAX1676)
♦ 8-Pin and 10-Pin µMAX Packages
te e d from 1.1V inp uts . The MAX1674/MAX1675/
MAX1676 have a preset, pin-selectable output for 5V or
3.3V. The outputs can also be adjusted to other volt-
ages using two external resistors.
♦ Preassembled Evaluation Kit (MAX1676EVKIT)
All thre e d e vic e s ha ve a 0.3Ω N-c ha nne l MOSFET
power switch. The MAX1674 has a 1A current limit. The
MAX1675 has a 0.5A current limit, which permits the
use of a smaller inductor. The MAX1676 comes in a
10-pin µMAX package and features an adjustable cur-
rent limit and circuitry to reduce inductor ringing.
_______________Ord e rin g In fo rm a t io n
PART
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8 µMAX
________________________Ap p lic a t io n s
MAX1674EUA
MAX1675EUA
MAX1676EUB
Pagers
8 µMAX
Wireless Phones
Medical Devices
Hand-Held Computers
PDAs
10 µMAX
RF Tags
P in Co n fig u ra t io n s
1 to 3-Cell Hand-Held Devices
TOP VIEW
Typ ic a l Op e ra t in g Circ u it
1
2
3
4
8
7
6
5
OUT
LX
FB
LBI
INPUT
0.7V TO V
OUT
MAX1674
MAX1675
LBO
REF
GND
SHDN
OUTPUT
3.3V, 5V, OR
ADJ (2V TO 5.5V)
UP TO 300mA
ON
SHDN
LX
OFF
µMAX
MAX1674
MAX1675
OUT
1
2
3
4
5
FB
LBI
10 OUT
9
8
7
6
LX
LOW-BATTERY
DETECT IN
LOW-BATTERY
DETECT OUT
MAX1676
LBI
LBO
LBO
GND
BATT
SHDN
REF
FB
GND
CLSEL
REF
0.1µF
µMAX
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
Hig h -Effic ie n c y, Lo w -S u p p ly-Cu rre n t ,
Co m p a c t , S t e p -Up DC-DC Co n ve rt e rs
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (OUT to GND) ..............................-0.3V to +6.0V
Switch Voltage (LX to GND) .....................-0.3V to (V + 0.3V)
Continuous Power Dissipation (T = +70°C)
8-Pin µMAX (derate 4.1mW/°C above +70°C) .............330mW
A
OUT
Battery Voltage (BATT to GND).............................-0.3V to +6.0V
SHDN, LBO to GND ..............................................-0.3V to +6.0V
10-Pin µMAX (derate 5.6mW/°C above +70°C) ...........444mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +165°C
Lead Temperature (soldering, 10sec) .............................+300°C
LBI, REF, FB, CLSEL to GND ...................-0.3V to (V
+ 0.3V)
OUT
Switch Current (LX)...............................................-1.5A to +1.5A
Output Current (OUT) ...........................................-1.5A to +1.5A
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
BATT
= 2V, FB = OUT (V
= 3.3V), R = ˙∞, T = 0°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)
OUT
L
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Minimum Input Voltage
Operating Voltage
0.7
V
V
V
IN
T
= +25°C
1.1
5.5
1.1
A
Start-Up Voltage
T
A
= +25°C, R = 3kΩ (Note 1)
0.9
-2
V
L
Start-Up Voltage Tempco
mV/°C
FB = OUT
FB = GND
3.17
4.80
2
3.30
5
3.43
5.20
5.5
Output Voltage
V
OUT
V
V
Output Voltage Range
MAX1674,
MAX1676 (CLSEL = OUT)
300
150
180
420
220
285
130
45/MAX176
FB = OUT
(V
OUT
= 3.3V)
MAX1675,
MAX1676 (CLSEL = GND)
Steady-State Output Current
(Note 2)
I
mA
OUT
MAX1674,
MAX1676 (CLSEL = OUT)
FB = GND
(V = 5V)
OUT
MAX1675,
MAX1676 (CLSEL = GND)
90
Reference Voltage
V
I
= 0
1.274
1.30
1.326
15
V
REF
REF
Reference Voltage Tempco
TEMPCO
0.024
mV/°C
Reference Voltage Load
Regulation
V
I
= 0 to 100µA
3
mV
REF_LOAD
REF
Reference Voltage Line
Regulation
V
V
= 2V to 5.5V
0.08
1.30
0.3
2.5
1.326
0.6
mV/V
V
REF_LINE
OUT
FB, LBI Input Threshold
1.274
Internal NFET, PFET
On-Resistance
R
I
LX
= 100mA
Ω
DS(ON)
MAX1674, MAX1676 (CLSEL = OUT)
MAX1675, MAX1676 (CLSEL = GND)
0.80
0.4
1
1.20
0.65
1
LX Switch Current
Limit (NFET)
I
A
LIM
0.5
LX Leakage Current
I
V
= 0, 5.5V; V = 5.5V
OUT
0.05
µA
LEAK
LX
2
_______________________________________________________________________________________
Hig h -Effic ie n c y, Lo w -S u p p ly-Cu rre n t ,
Co m p a c t , S t e p -Up DC-DC Co n ve rt e rs
45/MAX176
ELECTRICAL CHARACTERISTICS (continued)
(V
BATT
= 2V, FB = OUT (V
= 3.3V), R = ˙∞, T = 0°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)
OUT
L
A
A
PARAMETER
SYMBOL
CONDITIONS
= 3.3V
OUT
MIN
TYP
MAX
35
UNITS
µA
Operating Current into OUT
(Note 3)
V
FB
= 1.4V, V
16
Shutdown Current into OUT
0.1
90
1
µA
SHDN = GND
= 3.3V, I
V
= 200mA
LOAD
OUT
Efficiency
%
V
= 2V, I
= 1mA
85
OUT
LOAD
LX Switch On-Time
t
V
= 1V, V = 3.3V
OUT
3
4
7
1.2
50
50
3
µs
µs
ON
FB
LX Switch Off-Time
t
V
FB
= 1V, V = 3.3V
OUT
0.8
1
OFF
FB Input Current
I
V
FB
= 1.4V
= 1.4V
0.03
1
nA
nA
µA
nA
V
FB
LBI Input Current
I
V
LBI
LBI
CLSEL Input Current
SHDN Input Current
LBO Low Output Voltage
LBO Off Leakage Current
Damping Switch Resistance
I
MAX1676, CLSEL = OUT
1.4
0.07
0.2
0.07
88
CLSEL
I
V
V
= 0 or V
OUT
50
0.4
1
SHDN
SHDN
= 0, I
= 1mA
LBI
SINK
I
V
= 5.5V, V = 5.5V
µA
Ω
LBO
LBO
LBI
MAX1676, V
= 2V
150
BATT
V
0.2V
OUT
IL
V
V
SHDN Input Voltage
V
IH
0.8V
OUT
V
IL
0.2V
OUT
CLSEL Input Voltage
V
IH
0.8V
OUT
Note 1: Start-up voltage operation is guaranteed with the addition of a Schottky MBR0520 external diode between the input and
output.
Note 2: Steady-state output current indicates that the device maintains output voltage regulation under load. See Figures 5 and 6.
Note 3: Device is bootstrapped (power to the IC comes from OUT). This correlates directly with the actual battery supply.
ELECTRICAL CHARACTERISTICS
(V
BATT
= 2V, FB = OUT, R = ∞, T = -40°C to +85°C, unless otherwise noted.) (Note 4)
L
A
PARAMETER
SYMBOL
CONDITIONS
MIN
3.13
MAX
3.47
UNITS
FB = OUT
FB = GND
Output Voltage
V
OUT
V
4.75
5.25
Output Voltage Range
Reference Voltage
FB, LBI Thresholds
2.20
5.5
V
V
V
V
REF
I
= 0
1.2675
1.2675
1.3325
1.3325
REF
Internal NFET, PFET
On-Resistance
R
0.6
40
Ω
DS(ON)
Operating Current into OUT
(Note 3)
V
FB
= 1.4V, V
= 3.3V
µA
OUT
Shutdown Current into OUT
LX Switch On-Time
1
µA
µs
SHDN = GND
= 1V, V = 3.3V
OUT
t
V
2.7
7.0
ON
FB
LX Switch Off-Time
t
V
= 1V, V = 3.3V
OUT
0.75
0.75
0.36
1.25
1.25
0.69
µs
OFF
FB
MAX1674, MAX1676 (CLSEL = OUT)
MAX1675, MAX1676 (CLSEL = GND)
LX Switch Current
Limit (NFET)
I
A
LIM
_______________________________________________________________________________________
3
Hig h -Effic ie n c y, Lo w -S u p p ly-Cu rre n t ,
Co m p a c t , S t e p -Up DC-DC Co n ve rt e rs
ELECTRICAL CHARACTERISTICS (continued)
(V
BATT
= 2V, FB = OUT, R = ∞, T = -40°C to +85°C, unless otherwise noted.) (Note 4)
L
A
PARAMETER
SYMBOL
CONDITIONS
MIN
MAX
UNITS
µA
CLSEL Input Current
I
MAX1676, CLSEL = OUT
3
75
1
CLSEL
I
V
= 0 or V
nA
SHDN Input Current
SHDN
SHDN
OUT
I
V
LBO
= 5.5V, V = 5.5V
µA
LBO Off Leakage Current
LBO
LBI
Note 4: Specifications to -40°C are guaranteed by design, not production tested.
Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(L = 22µH, C = 47µF, C
= 47µF 0.1µF, C
= 0.1µF, T = +25°C, unless otherwise noted.)
IN
OUT
REF
A
EFFICIENCY vs. LOAD CURRENT
EFFICIENCY vs. LOAD CURRENT
EFFICIENCY vs. LOAD CURRENT
100
100
100
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
V
= 3.6V
IN
V
= 2.4V
V
IN
= 2.4V
V = 2.4V
IN
IN
V
= 3.6V
V = 1.2V
IN
IN
V
IN
= 1.2V
V = 1.2V
IN
45/MAX176
V
I
= 5V
= 500mA
V
= 5V
= 1A
V = 3.3V
OUT
I = 500mA
LIMIT
OUT
OUT
I
LIMIT
LIMIT
0
0
0
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
1000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
REFERENCE OUTPUT VOLTAGE
vs. TEMPERATURE
EFFICIENCY vs. LOAD CURRENT
100
1.300
1.298
1.296
1.294
1.292
1.290
90
80
70
60
50
40
30
20
10
V
= 2.4V
IN
I
REF
= 0
V
IN
= 1.2V
I
REF
= 100µA
V
= 3.3V
= 1A
OUT
I
LIMIT
0
-40 -20
0
20
40
60
80 100
0.01
0.1
1
10
100
1000
TEMPERATURE (°C)
LOAD CURRENT (mA)
4
_______________________________________________________________________________________
Hig h -Effic ie n c y, Lo w -S u p p ly-Cu rre n t ,
Co m p a c t , S t e p -Up DC-DC Co n ve rt e rs
45/MAX176
Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
= 47µF 0.1µF, C = 0.1µF, T = +25°C, unless otherwise noted.)
REF A
(L = 22µH, C = 47µF, C
IN
OUT
SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE
NO-LOAD BATTERY CURRENT
vs. INPUT BATTERY VOLTAGE
START-UP VOLTAGE
vs. LOAD CURRENT
1.0
160
140
120
100
80
1.8
1.6
0.8
0.6
1.4
1.2
1.0
0.8
0.6
I
= 1A, 5.0V
LIMIT
0.4
WITHOUT DIODE
WITH 1N5817
0.2
0
I
= 0.5A, 5.0V
LIMIT
-0.2
-0.4
-0.6
-0.8
-1.0
60
40
I
= 0.5A, 3.3V
LIMIT
0.4
0.2
0
20
I
= 1A, 3.3V
LIMIT
0
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
INPUT BATTERY VOLTAGE (V)
1
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
SUPPLY VOLTAGE (V)
0.01
0.1
1
10
100
LOAD CURRENT (mA)
SHUTDOWN THRESHOLD
vs. SUPPLY VOLTAGE
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE (V = 3.3V)
OUT
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE (V = 5V)
OUT
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
800
700
600
500
400
300
200
100
0
900
800
700
600
500
400
300
200
100
0
1A CURRENT LIMIT
1A CURRENT LIMIT
0.5A CURRENT LIMIT
0.5A CURRENT LIMIT
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
SUPPLY VOLTAGE (V)
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
INPUT VOLTAGE (V)
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
INPUT VOLTAGE (V)
LX CURRENT LIMIT
vs. OUTPUT VOLTAGE
HEAVY-LOAD SWITCHING WAVEFORMS
SWITCH RESISTANCE vs. TEMPERATURE
MAX1674 TOC13
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
1.2
1.0
0.8
0.6
0.4
0.2
0
MAX1674, MAX1676 (CLSEL = OUT)
P-CHANNEL
V
5V/div
LX
I
LX
0.5A/div
N-CHANNEL
MAX1675, MAX1676 (CLSEL = GND)
V
OUT
AC COUPLED
100mV/div
V = 2.4V
IN
V
= 5.0V
OUT
1µs/div
-40
2.0
2.5
3.0
OUTPUT VOLTAGE (V)
3.5
4.0
4.5
5.0
-60
-20
0
20 40 60 80 100
TEMPERATURE (°C)
_______________________________________________________________________________________
5
Hig h -Effic ie n c y, Lo w -S u p p ly-Cu rre n t ,
Co m p a c t , S t e p -Up DC-DC Co n ve rt e rs
Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(L = 22µH, C = 47µF, C
= 47µF 0.1µF, C
= 0.1µF, T = +25°C, unless otherwise noted.)
IN
OUT
REF
A
LINE-TRANSIENT RESPONSE
LOAD-TRANSIENT RESPONSE
EXITING SHUTDOWN
MAX1674 TOC17
MAX1674 TOC15
MAX1674 TOC16
V = 2.4V
IN
V
IN
V
= 3.3V
OUT
V
2V/div
OUT
2V TO 3V
1V/div
I
OUT
200mA/div
V
SHDN
2V/div
V
OUT
V
OUT
50mV/div
AC
COUPLED
AC COUPLED
100mV/div
I
LOAD
100mA
10µs/div
5µs/div
500µs/div
P in De s c rip t io n
PIN
NAME
FUNCTION
MAX1674
MAX1675
MAX1676
Dual-Mode™ Feedback Input. Connect to GND for +5.0V output.
Connect to OUT for +3.3V output. Use a resistor network to set the
output voltage from +2.0V to +5.5V.
45/MAX176
1
1
FB
2
3
2
3
LBI
Low-Battery Comparator Input. Internally set to trip at +1.30V.
Open-Drain Low-Battery Comparator Output. Output is low when
LBO
V
is <1.3V. LBO is high impedance during shutdown.
LBI
Current-Limit Select Input. CLSEL = OUT sets the current limit to 1A.
CLSEL = GND sets the current limit to 0.5A.
—
4
CLSEL
4
5
5
6
REF
1.3V Reference Voltage. Bypass with a 0.1µF capacitor.
Shutdown Input. High = operating, low = shutdown.
SHDN
Battery Input and Damping Switch Connection. If damping switch is
unused, leave BATT unconnected.
—
7
BATT
6
7
8
8
9
GND
LX
Ground
N-Channel and P-Channel Power MOSFET Drain
Power Output. OUT provides bootstrap power to the IC.
10
OUT
Dual-Mode is a trademark of Maxim Integrated Products.
6
_______________________________________________________________________________________
Hig h -Effic ie n c y, Lo w -S u p p ly-Cu rre n t ,
Co m p a c t , S t e p -Up DC-DC Co n ve rt e rs
45/MAX176
combines the high output power and efficiency of a
pulse-width-modulation (PWM) device with the ultra-low
De t a ile d De s c rip t io n
The MAX1674/MAX1675/MAX1676 compact, step-up
quiescent current of a traditional PFM (Figure 1). There
is no oscillator; a constant-peak-current limit in the
switch allows the inductor current to vary between this
peak limit and some lesser value. At light loads, the
switching frequency is governed by a pair of one-shots
that set a typical minimum off-time (1µs) and a typical
ma ximum on-time (4µs ). The s witc hing fre q ue nc y
depends upon the load and the input voltage, and can
range up to 500kHz. The peak current of the internal N-
c ha nne l MOSFET p owe r s witc h is fixe d a t 1A
(MAX1674), a t 0.5A (MAX1675), or is s e le c ta b le
(MAX1676). Unlike conventional pulse-skipping DC-DC
converters (where ripple amplitude varies with input
voltage), ripple in these devices does not exceed the
product of the switch current limit and the filter-capaci-
tor equivalent series resistance (ESR).
DC-DC converters start up with voltages as low as 0.9V
a nd op e ra te with a n inp ut volta g e d own to 0.7V.
Cons uming only 16µA of q uie s c e nt c urre nt, the s e
d e vic e s offe r a b uilt-in s ync hronous re c tifie r tha t
reduces cost by eliminating the need for an external
diode and improves overall efficiency by minimizing
losses in the circuit (see Synchronous Rectification sec-
tion for details). The internal MOSFET resistance is typi-
cally 0.3Ω, which minimizes losses. The current limit of
the MAX1674 and MAX1675 are 1A and 0.5A, respec-
tively. The MAX1675’s lower current limit allows the use
of a p hys ic a lly s ma lle r ind uc tor in s p a c e -s e ns itive
applications. The MAX1676 features a circuit that elimi-
nates noise due to inductor ringing. In addition, the
MAX1676 offers a selectable current limit (0.5A or 1A)
for design flexibility.
S yn c h ro n o u s Re c t ific a t io n
The internal synchronous rectifier eliminates the need
for an external Schottky diode, thus reducing cost and
board space. During the cycle off-time, the P-channel
MOSFET turns on and shunts the MOSFET body diode.
P FM Co n t ro l S c h e m e
A unique minimum-off-time, current-limited, pulse-fre-
quency-modulation (PFM) control scheme is a key fea-
ture of the MAX1674/MAX1675/MAX1676. This scheme
0.1µF
47µF
OUT
V
OUT
MINIMUM
OFF-TIME
ONE-SHOT
ZERO
CROSSING
AMPLIFIER
EN
SHDN
Q
TRIG
ONE-SHOT
P
V
IN
LX
22µH
47µF
N
F/F
CLSEL
GND
Q
S
R
(MAX1676)
MAX1674
MAX1675
MAX1676
MAXIMUM
ON-TIME
R1
200Ω
BATT
ONE-SHOT
CURRENT-LIMIT
AMPLIFIER
TRIG
Q
(MAX1676)
DAMPING
V
OUT
V
IN
ONE-SHOT
R5
SWITCH
R3
ERROR
AMPLIFIER
FB
R2
100k
R6
REFERENCE
LBO
LBI
LOW-BATTERY
COMPARATOR
REF
R4
0.1µF
Figure 1. Simplified Functional Diagram
_______________________________________________________________________________________
7
Hig h -Effic ie n c y, Lo w -S u p p ly-Cu rre n t ,
Co m p a c t , S t e p -Up DC-DC Co n ve rt e rs
As a re s ult, the s ync hronous re c tifie r s ig nific a ntly
improves efficiency without the addition of an external
component. Conversion efficiency can be as high as
94%, as shown in the Typical Operating Characteristics.
For low-voltage inputs from single cells (Alkaline, NiCd,
V
IN
R1
200Ω
or NiMH), use an external Schottky diode such as the
1N5817 to ensure start-up.
BATT
22µH
MAX1676
Vo lt a g e Re fe re n c e
The volta g e a t REF is nomina lly + 1.30V. REF c a n
source up to 100µA to external circuits. The reference
maintains excellent load regulation (see Typical Oper-
ating Characteristics). A bypass capacitor of 0.1µF is
required for proper operation.
DAMPING
SWITCH
LX
OUT
V
OUT
0.1µF
47µF
S h u t d o w n
The d e vic e e nte rs s hutd own whe n V
is low.
SHDN
During shutdown, the body diode of the P-channel
MOSFET allows current flow from the battery to the out-
Figure 2. Simplified Diagram of Inductor Damping Switch
put. V
falls to approximately V - 0.6V and LX
OUT
IN
remains high impedance. The capacitance and load at
OUT d e te rmine the ra te a t whic h V d e c a ys .
OUT
Shutdown can be pulled as high as 6V, regardless of
the voltage at OUT.
Cu rre n t Lim it S e le c t P in (MAX1 6 7 6 )
The MAX1676 allows a selectable inductor current limit
of either 0.5A or 1A. This allows flexibility in designing
for higher current applications or for smaller, compact
designs. Connect CLSEL to OUT for 1A or to GND for
0.5A. CLSEL draws 1.4µA when connected to OUT.
V
1V/div
LX
45/MAX176
BATT/Da m p in g S w it c h (MAX1 6 7 6 )
The MAX1676 is designed with an internal damping
switch to minimize ringing at LX. The damping switch
connects an external resistor (R1) across the inductor
whe n the ind uc tor’s e ne rg y is d e p le te d (Fig ure 2).
Normally, when the energy in the inductor is insufficient
to supply current to the output, the capacitance and
inductance at LX form a resonant circuit that causes
ringing. The ringing continues until the energy is dissi-
pated through the series resistance of the inductor. The
damping switch supplies a path to quickly dissipate this
energy, minimizing the ringing at LX. Damping LX ring-
2µs/div
Figure 3. LX Ringing Without Damping Switch
ing does not reduce V
ripple, but does reduce EMI.
V
1V/div
OUT
LX
R1 = 200Ω works well for most applications while reduc-
ing efficiency by only 1%. Larger R1 values provide less
damping, but have less impact on efficiency. Generally,
lower values of R1 are needed to fully damp LX when
the V
/V ratio is high (Figures 2, 3, and 4).
OUT IN
2µs/div
Figure 4. LX Waveform with Damping Switch (with 200Ω
external resistor)
8
_______________________________________________________________________________________
Hig h -Effic ie n c y, Lo w -S u p p ly-Cu rre n t ,
Co m p a c t , S t e p -Up DC-DC Co n ve rt e rs
45/MAX176
where V
= +1.3V and V
may range from 2V to
S e le c t in g t h e Ou t p u t Vo lt a g e
REF
OUT
5V. The input bias current of FB has a maximum value
of 50nA which allows large-value resistors (R6 ≤ 260kΩ)
to be used.
V
can be set to 3.3V or 5.5V by connecting the FB
OUT
pin to GND (5V) or OUT (3.3V) (Figures 5 and 6).
To adjust the output voltage, connect a resistor-divider
from V
to FB to GND (Figure 7). Choose a value
OUT
Lo w -Ba t t e ry De t e c t io n
The MAX1674/MAX1675/MAX1676 contain an on-chip
comparator for low-battery detection. If the voltage at
LBI falls below the internal reference voltage (1.30V),
LBO (an open-drain output) sinks current to GND. The
low-battery monitor threshold is set by two resistors, R3
and R4 (Figures 5, 6, and 7). Since the LBI current is
less than 50nA, large resistor values (R4 ≤ 260kΩ) can
b e us e d to minimize loa d ing of the inp ut s up p ly.
Calculate R3 using the following equation:
less than 260kΩ for R6. Use the following equation to
calculate R5:
R5 = R6 [(V
/ V
) - 1]
OUT
REF
V
IN
47µF
10V
22µH
R3 = R4 [(V
/ V ) - 1]
REF
TRIP
R1
for V
≥ 1.3V. V
is the level where the low-battery
200Ω
TRIP
TRIP
BATT
(MAX1676)
LX
d e te c tor outp ut g oe s low, a nd V
is the inte rna l
REF
V
OUT
+3.3V
200mA
1.30V reference. Connect a pull-up resistor of 100kΩ or
greater from LBO to OUT when driving CMOS circuits.
LBO is an open-drain output, and can be pulled as
high as 6V regardless of the voltage at OUT. When LBI
is above the threshold, the LBO output is high imped-
ance. If the low-battery comparator is not used, ground
OUT
R3
R4
CLSEL
(MAX1676)
0.1µF
47µF
LBI
FB
SHDN
R2
100k
MAX1674
MAX1675
MAX1676
LOW-BATTERY
OUTPUT
REF
LBO
V
IN
GND
0.1µF
Figure 5. Preset Output Voltage of +3.3V
47µF
22µH
V
IN
R1
200Ω
BATT
LX
(MAX1676)
OUTPUT
47µF
OUT
2V to 5.5V
R3
R4
22µH
R1
SHDN
0.1µF
47µF
200Ω
LBI
CLSEL
(MAX1676)
BATT
LX
(MAX1676)
OUTPUT
5.0V,
150mA
R5
R2
100k
OUT
R3
CLSEL
LOW-
BATTERY
OUTPUT
MAX1674
MAX1675
MAX1676
(MAX1676)
LBO
FB
0.1µF
47µF
LBI
SHDN
R4
R2
100k
REF
GND
LOW-
BATTERY
OUTPUT
MAX1674
MAX1675
MAX1676
LBO
FB
0.1µF
R6
REF
GND
0.1µF
Figure 6. Preset Output Voltage of +5V
_______________________________________________________________________________________
Figure 7. Setting an Adjustable Output
9
Hig h -Effic ie n c y, Lo w -S u p p ly-Cu rre n t ,
Co m p a c t , S t e p -Up DC-DC Co n ve rt e rs
V
IN
V
(V , V )
TRIP H L
V
OUT
MAX1674
MAX1675
MAX1676
OUT
R3
R4
47µF
22µH
0.1µF
47µF
R1
LBI
200Ω
R2
100k
BATT
LX
(MAX1676)
V
OUT
OUT
R3
CLSEL
(MAX1676)
LBO
0.1µF
47µF
LBI
FB
GND
R7
SHDN
R2
MAX1674
MAX1675
MAX1676
100k
R4
R3
R3
R4
LOW-
BATTERY
OUTPUT
V
=
=
1.3V 1 +
+
−
(
)
H
REF
R7
LBO
GND
(V
− 1.3V) R3
R3
R4
OUT
V
1.3V 1 +
(
)
L
0.1µF
(1.3V) (R2 + R7)
WHERE V IS THE UPPER TRIP LEVEL
H
V IS THE LOWER TRIP LEVEL
L
Figure 8. Setting Resistor Values for the Low-Battery Indicator
Figure 9. Adding External Hysteresis to the Low-Battery
Indicator
when V < 1.3V
IN
MAX1674, 500mA for the MAX1675, and 1A or 0.5A for
the MAX1676. However, it is generally acceptable to
bias the inductor into saturation by as much as 20%,
although this will slightly reduce efficiency. Table 1 lists
suggested components.
LBI and LBO. For V
comparator as shown in Figure 8. Calculate the value of
the external resistors R3 and R4 as follows:
less than 1.3V, configure the
TRIP
45/MAX176
R3 = R4(V
- V
) / (V
- V
)
REF
TRIP
OUT
REF
Since the low-battery comparator is noninverting, exter-
nal hysteresis can be added by connecting a resistor
between LBO and LBI as shown in Figure 9. When LBO
is high, the series combination of R2 and R7 source
current into the LBI summing junction.
The inductor’s DC resistance significantly affects effi-
ciency. See Table 2 for a comparison of inductor speci-
fications. Calculate the maximum output current as
follows:
Ap p lic a t io n s In fo rm a t io n
V
– V
BATT
OUT
V
I
– 1/ 2
η
In d u c t o r S e le c t io n
An inductor value of 22µH performs well in most appli-
cations. The MAX1674/MAX1675/MAX1676 will also
work with inductors in the 10µH to 47µH range. Smaller
inductance values typically offer a smaller physical size
for a given series resistance, allowing the smallest
overall circuit dimensions. However, due to higher peak
BATT LIM
L
+ R
P
t
OFF
I
=
OUT MAX
(
)
V
OUT
where I
= maximum output current in amps
OUT(MAX)
V
BATT
= input voltage
inductor currents, the output voltage ripple (I
x
PEAK
output filter capacitor ESR) also tends to be higher.
Circuits using larger inductance values exhibit higher
output current capability and larger physical dimen-
sions for a given series resistance. The inductor’s incre-
mental saturation current rating should be greater than
the p e a k s witc h-c urre nt limit, whic h is 1A for the
L = inductor value in µH
η= efficiency (typically 0.9)
t
= LX switch’s off-time in µs
OFF
R = resistance of P-channel MOSFET in Ω
P
I
= 0.5A or 1.0A
LIM
10 ______________________________________________________________________________________
Hig h -Effic ie n c y, Lo w -S u p p ly-Cu rre n t ,
Co m p a c t , S t e p -Up DC-DC Co n ve rt e rs
45/MAX176
Table 1. Suggested Components
PRODUCTION
METHOD
RECTIFIERS
(OPTIONAL)
INDUCTORS
CAPACITORS
Sumida CD43 series
Sumida CD54 series
Coilcraft DT1608C
Coilcraft DO1608C
Coiltronics Uni-PAC
Murata LQH4 series
Sprague 593D series
Sprague 595D series
AVX TPS series
ceramic
Motorola MBR0530
Nihon EC 15QS02L
Surface Mount
Miniature Through-Hole
Sumida RCH654-220
Sanyo OS-CON series
—
Table 2. Surface-Mount Inductor
Specifications
Table 3. Component Suppliers
COMPANY
AVX
PHONE
FAX
USA (803) 946-0690
USA (847) 639-6400
USA (561) 241-7876
USA (803) 626-3123
USA (847) 639-1469
USA (561) 241-9339
MANUFACTURER
PART NUMBER
HEIGHT
(mm)
µH Ω (max) I
(A)
PEAK
Coilcraft
Coiltronics
Coilcraft DT1608C-103 10
Coilcraft DO1608C-153 15
Coilcraft DO1608C-223 22
0.095
0.200
0.320
0.111
0.175
0.254
0.560
0.560
0.132
0.182
0.100
0.150
0.180
0.7
0.9
0.7
1.9
1.5
1.2
0.4
0.4
2.92
2.92
2.92
5.0
5.0
5.0
2.6
2.6
3.2
3.2
4.5
4.5
4.5
USA (303) 675-2140
(800) 521-6274
Motorola
Murata
Nihon
USA (303) 675-2150
USA (814) 238-0490
USA (814) 237-1431
(800) 831-9172
Coiltronics UP1B-100
Coiltronics UP1B-150
Coiltronics UP1B-220
Murata LQH4N100
Murata LQH4N220
Sumida CD43-8R2
Sumida CD43-100
Sumida CD54-100
Sumida CD54-180
Sumida CD54-220
10
15
22
10
22
8.2
10
10
18
22
USA (805) 867-2555 USA (805) 867-2556
Japan 81-3-3494-7411 Japan 81-3-3494-7414
USA (619) 661-6835
Japan 81-7-2070-6306 Japan 81-7-2070-1174
USA (619) 661-1055
Sanyo
1.26
1.15
1.44
1.23
1.11
Sprague
Sumida
USA (603) 224-1961
USA (647) 956-0666
USA (603) 224-1430
USA (647) 956-0702
Japan 81-3-3607-5111 Japan 81-3-3607-5144
Taiyo Yuden USA (408) 573-4150
USA (408) 573-4159
inductor current and the output capacitor ESR. Use
low-ESR capacitors for best performance, or connect
two or more filter capacitors in parallel. Low-ESR, SMT
ta nta lum c a p a c itors a re c urre ntly a va ila b le from
Sprague (595D series) AVX (TPS series) and other
sources. Ceramic surface-mount and Sanyo OS-CON
organic-semiconductor through-hole capacitors also
exhibit very low ESR, and are especially useful for oper-
ation at cold temperatures. See Table 3 for a list of sug-
gested component suppliers.
Ca p a c it o r S e le c t io n
A 47µF, 10V surface-mount tantalum (SMT) output filter
capacitor provides 80mV output ripple when stepping
up from 2V to 5V. Smaller capacitors (down to 10µF
with higher ESRs) are acceptable for light loads or in
a p p lic a tions tha t c a n tole ra te hig he r outp ut rip p le .
Values in the 10µF to 100µF range are recommended.
The equivalent series resistance (ESR) of both bypass
and filter capacitors affects efficiency and output rip-
ple. Output voltage ripple is the product of the peak
______________________________________________________________________________________ 11
Hig h -Effic ie n c y, Lo w -S u p p ly-Cu rre n t ,
Co m p a c t , S t e p -Up DC-DC Co n ve rt e rs
Op t io n a l Ex t e rn a l Re c t ifie r
Although not required, a Schottky diode (such as the
MBR0520) connected between LX and OUT allows
lower start-up voltages (Figure 10) and is recommend-
ed for single-cell operation. Note that adding this diode
provides no significant efficiency improvement.
R1
V
SINGLE CELL
IN
47µF
22µH
200Ω
P C Bo a rd La yo u t a n d Gro u n d in g
BATT
LX
(MAX1676)
Careful printed circuit layout is important for minimizing
ground bounce and noise. Keep the IC’s GND pin and
the ground leads of the input and output filter capaci-
tors less than 0.2in (5mm) apart. In addition, keep all
connections to the FB and LX pins as short as possi-
ble. In particular, when using external feedback resis-
tors, locate them as close to the FB as possible. To
maximize output power and efficiency and minimize
output ripple voltage, use a ground plane and solder
the IC’s GND directly to the ground plane.
MBR0520
OUT
FB
R3
R4
MAX1674
MAX1675
MAX1676
0.1µF
47µF
LBI
SHDN
R2
100k
CLSEL
(MAX1676)
LOW-BATTERY
OUTPUT
LBO
REF
GND
0.1µF
Figure 10. Adding a Schottky Diode for Single-Cell Operation
Ch ip In fo rm a t io n
TRANSISTOR COUNT: 751
P a c k a g e In fo rm a t io n
45/MAX176
12
______________________________________________________________________________________
MAX1674-MAX1676 相关器件
| 型号 | 制造商 | 描述 | 价格 | 文档 |
| MAX1674/MAX1675/MAX1676 | MAXIM | High-Efficiency Low-Supply-Current Compact Step-Up DC- | 获取价格 |
|
| MAX1674EUA | MAXIM | High-Efficiency, Low-Supply-Current, Compact, Step-Up DC-DC Converters | 获取价格 |
|
| MAX1674EUA+T | MAXIM | Switching Regulator, Voltage-mode, 1.5A, 500kHz Switching Freq-Max, PDSO8, UMAX-8 | 获取价格 |
|
| MAX1674EUA-T | MAXIM | Switching Regulator, Voltage-mode, 1.5A, 500kHz Switching Freq-Max, PDSO8, UMAX-8 | 获取价格 |
|
| MAX1675 | MAXIM | 375MHz Quad Closed Loop Video Buffers.Av = +1 and +2[MAX496/MAX497/MAX496/MAX497/MAX496/MAX497/MAX496C/D/MAX496CPE/MAX496CSE/MAX496CSE-T/MAX497C/D/MAX497CPE/MAX497CSE/MAX497CSE-T/MAX497EVKIT-SO ] | 获取价格 |
|
| MAX1675 | ADI | 高效率、低电源电流、紧凑的、升压型DC-DC转换器 | 获取价格 |
|
| MAX1675EUA | MAXIM | High-Efficiency, Low-Supply-Current, Compact, Step-Up DC-DC Converters | 获取价格 |
|
| MAX1675EUA+ | MAXIM | Switching Regulator, Voltage-mode, 1.5A, 500kHz Switching Freq-Max, PDSO8, UMAX-8 | 获取价格 |
|
| MAX1675EUA+T | MAXIM | Switching Regulator, Voltage-mode, 1.5A, 500kHz Switching Freq-Max, PDSO8, UMAX-8 | 获取价格 |
|
| MAX1676 | MAXIM | 375MHz Quad Closed Loop Video Buffers.Av = +1 and +2[MAX496/MAX497/MAX496/MAX497/MAX496/MAX497/MAX496C/D/MAX496CPE/MAX496CSE/MAX496CSE-T/MAX497C/D/MAX497CPE/MAX497CSE/MAX497CSE-T/MAX497EVKIT-SO ] | 获取价格 |
|
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