General Description
The MAX1790/MAX8715 boost converters incorporate
high-performance (at 1.2MHz), current-mode, fixed-fre-
quency, pulse-width modulation (PWM) circuitry with a
built-in 0.21
/0.15 n-channel MOSFET to provide a high-
ly efficient regulator with fast response.
High switching frequency (640kHz or 1.2MHz selectable)
allows easy filtering and faster loop performance. An
external compensation pin provides the user flexibility in
determining loop dynamics, allowing the use of small, low
equivalent-series-resistance (ESR) ceramic output capaci-
tors. The device can produce an output voltage as high as
12V from an input as low as 2.6V.
Soft-start is programmed with an external capacitor, which
sets the input-current ramp rate. In shutdown mode, cur-
rent consumption is reduced to 0.1µA. The MAX1790/
MAX8715 are available in a space-saving 8-pin µMAX
®
package. The ultra-small package and high switching fre-
quency allow the total solution to be less than 1.1mm high.
Applications
LCD Displays
PCMCIA Cards
Portable Applications
Hand-Held Devices
Features
90% Efficiency
Adjustable Output from V
IN
to 12V
1.6A, 0.21, 14V Power MOSFET (MAX1790)
2.4A, 0.15, 14V Power MOSFET (MAX8715)
+2.6V to +5.5V Input Range
Pin-Selectable 640kHz or 1.2MHz Switching
Frequency
0.1µA Shutdown Current
Programmable Soft-Start
Small 8-Pin µMAX Package
MAX1790/MAX8715
Low-Noise Step-Up DC-DC Converters
________________________________________________________________ Maxim Integrated Products
1
IN
LX
GND
1
2
8
7
SS
FREQ
FB
COMP
MAX
TOP VIEW
3
4
6
5
MAX1790
MAX8715
SHDN
LX
IN
V
IN
2.6V TO 5V
GND
FREQ
V
OUT
COMP
SHDN
FB
MAX1790
MAX8715
ON/OFF
SS
Typical Operating Circuit
19-1563; Rev 3; 9/05
Pin Configuration
Ordering Information
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.
EVALUATION KIT
AVAILABLE
PART
TEMP RANGE
PIN-PACKAGE
MAX1790EUA
-40°C to +85°C
8 µMAX
MAX1790EUA+
-40°C to +85°C
8 µMAX
MAX8715EUA
-40°C to +85°C
8 µMAX
MAX8715EUA+
-40°C to +85°C
8 µMAX
µMAX is a registered trademark of Maxim Integrated Products,
Inc.
+ Denotes lead-free package.
MAX1790/MAX8715
Low-Noise Step-Up DC-DC Converters
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
IN
=
SHDN = 3V, FREQ = GND, T
A
= 0°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
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.
LX to GND ..............................................................-0.3V to +14V
IN,
SHDN, FREQ, FB to GND ................................-0.3V to +6.2V
SS, COMP to GND .......................................-0.3V to (V
IN
+ 0.3V)
RMS LX Pin Current ..............................................................1.2A
Continuous Power Dissipation (T
A
= +70°C)
8-Pin µMAX (derate 4.1mW/°C above +70°C) .............330mW
Operating Temperature Range
MAX1790EUA/MAX8715EUA ........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Input Supply Range
V
IN
2.6
5.5
V
V
IN
Undervoltage Lockout
UVLO
V
IN
rising, typical hysteresis is 40mV,
LX remains off below this level
2.25
2.38
2.52
V
V
FB
= 1.3V, not switching
0.18
0.35
MAX1790
V
FB
= 1.0V, switching
2
5
V
FB
= 1.3V, not switching
0.21
0.35
Quiescent Current
I
IN
MAX8715
V
FB
= 1.0V, switching
2.5
5.0
mA
Shutdown Supply Current
I
IN
SHDN = GND
0.1
10
µA
ERROR AMPLIFIER
Feedback Voltage
V
FB
Level to produce V
COMP
= 1.24V
1.222
1.24
1.258
V
MAX1790
0
40
FB Input Bias Current
I
FB
V
FB
= 1.24V
MAX8715
125
190
nA
Feedback-Voltage Line
Regulation
Level to produce V
COMP
= 1.24V,
2.6V < V
IN
< 5.5V
0.05
0.15
%/V
MAX1790
70
140
240
Transconductance
g
m
I = 5µA
MAX8715
70
160
240
µS
Voltage Gain
A
V
700
V/V
OSCILLATOR
FREQ = GND
540
640
740
Frequency
f
OSC
FREQ = IN
1000
1220
1500
kHz
FREQ = GND
79
85
92
Maximum Duty Cycle
DC
FREQ = IN
84
%
N-CHANNEL SWITCH
MAX1790
1.2
1.6
2.3
Current Limit
I
LIM
V
FB
= 1V,
duty cycle =
65% (Note 1)
MAX8715
1.8
2.4
3.4
A
MAX1790
0.21
0.5
On-Resistance
R
ON
MAX8715
0.15
0.35
MAX1790
0.01
20
Leakage Current
I
LXOFF
V
LX
= 12V
MAX8715
5
30
µA
MAX1790/MAX8715
Low-Noise Step-Up DC-DC Converters
_______________________________________________________________________________________
3
ELECTRICAL CHARACTERISTICS
(V
IN
=
SHDN = 3V, FREQ = GND, T
A
= -40°C to +85°C, unless otherwise noted.) (Note 2)
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
=
SHDN = 3V, FREQ = GND, T
A
= 0°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1790
0.30
0.45
0.65
Current-Sense Transresistance
R
CS
MAX8715
0.20
0.30
0.43
V/A
SOFT-START
Reset Switch Resistance
100
Charge Current
V
SS
= 1.2V
1.5
4
7.0
µA
CONTROL INPUTS
Input Low Voltage
V
IL
SHDN, FREQ
0.3 x V
IN
V
Input High Voltage
V
IH
SHDN, FREQ
0.7 x V
IN
V
Hysteresis
SHDN, FREQ
0.1 x V
IN
V
FREQ Pulldown Current
I
FREQ
1.8
5
9.0
µA
SHDN Input Current
I
SHDN
0.001
1
µA
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Input Supply Range
V
IN
2.6
5.5
V
V
IN
Undervoltage Lockout
UVLO
V
IN
rising, typical hysteresis is 40mV,
LX remains off below this level
2.25
2.52
V
V
FB
= 1.3V, not switching
0.35
MAX1790
V
FB
= 1.0V, switching
5
V
FB
= 1.3V, not switching
0.35
Quiescent Current
I
IN
MAX8715
V
FB
= 1.0V, switching
5
mA
Shutdown Supply Current
I
IN
SHDN = GND
10
µA
ERROR AMPLIFIER
Feedback Voltage
V
FB
Level to produce V
COMP
= 1.24V
1.215
1.24
1.260
V
MAX1790
40
FB Input Bias Current
I
FB
V
FB
= 1.24V
MAX8715
190
nA
Feedback-Voltage Line
Regulation
Level to produce V
COMP
= 1.24V,
2.6V < V
IN
< 5.5V
0.15
%/V
MAX1790
70
260
Transconductance
g
m
I = 5µA
MAX8715
70
260
µS
OSCILLATOR
FREQ = GND
490
770
Frequency
f
OSC
FREQ = IN
900
1500
kHz
Maximum Duty Cycle
DC
FREQ = GND
78
92
%
MAX1790/MAX8715
Low-Noise Step-Up DC-DC Converters
4
_______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
=
SHDN = 3V, FREQ = GND, T
A
= -40°C to +85°C, unless otherwise noted.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
N-CHANNEL SWITCH
MAX1790
1.2
2.3
Current Limit
I
LIM
V
FB
= 1V,
duty cycle =
65% (Note 1)
MAX8715
1.8
3.0
A
MAX1790
0.5
On-Resistance
R
ON
MAX8715
0.35
MAX1790
0.30
0.65
Current-Sense Transresistance
R
CS
MAX8715
0.20
0.43
V/A
CONTROL INPUTS
Input Low Voltage
V
IL
SHDN, FREQ
0.3 x V
IN
V
Input High Voltage
V
IH
SHDN, FREQ
0.7 x V
IN
V
Note 1: Current limit varies with duty cycle due to slope compensation. See the Output-Current Capability section.
Note 2: Specifications to -40°C are guaranteed by design and not production tested.
Typical Operating Characteristics
(Circuit of Figure 1, V
IN
= 3.3V, f
OSC
= 640kHz, T
A
= +25°C, unless otherwise noted.)
MAX1790 toc01
50
1
1000
100
10
MAX1790 EFFICIENCY
vs. OUTPUT CURRENT
65
55
85
75
95
70
60
90
80
OUTPUT CURRENT (mA)
EFFICIENCY (%)
f
OSC
= 1.2MHz
L
= 2.7
H
V
IN
= 3.3V
V
OUT
= 5V
f
OSC
= 640kHz
L
= 5.4
H
50
1
1000
100
10
MAX1790 EFFICIENCY
vs. OUTPUT CURRENT
65
55
85
75
95
70
60
90
80
MAX1790 toc02
OUTPUT CURRENT (mA)
EFFICIENCY (%)
f
OSC
= 1.2MHz
L
= 5.4
H
V
IN
= 3.3V
V
OUT
= 12V
f
OSC
= 640kHz
L
= 10
H
OUTPUT CURRENT (mA)
50
1
1000
100
10
MAX1790 EFFICIENCY
vs. OUTPUT CURRENT
65
55
85
75
95
70
60
90
80
MAX1790 toc03
EFFICIENCY (%)
f
OSC
= 1.2MHz
L
= 5.4
H
V
IN
= 5V
V
OUT
= 12V
f
OSC
= 640kHz
L
= 10
H
0
0.2
0.1
0.4
0.3
0.6
0.5
0.7
2.5
3.5
4.0
3.0
4.5
5.0
5.5
NO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX1790 toc04
INPUT VOLTAGE (V)
NO-LOAD SUPPLY CURRENT (mA)
V
OUT
= 12V
f
OSC
= 1.2MHz
f
OSC
= 640kHz
11.60
11.70
11.65
11.80
11.75
11.90
11.85
11.95
12.05
12.00
12.10
0
40 60 80
20
100 120 140
180
160
200
MAX1790 OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX1790 toc05
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
f
OSC
= 640kHz
T
A
= +85
°C
T
A
= +25
°C
T
A
= -40
°C
MAX8715 EFFICIENCY
vs. OUTPUT CURRENT
MAX1790 toc06
OUTPUT CURRENT (mA)
EFFICIENCY (%)
100
10
50
55
60
65
70
75
80
85
90
95
45
1
1000
V
IN
= 5.0V
V
IN
= 3.3V
V
OUT
= 9V
f
OSC
= 1.2MHz
L = 6.8
H
MAX1790/MAX8715
Low-Noise Step-Up DC-DC Converters
_______________________________________________________________________________________
5
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