19-1563; Rev 3; 9/05
IT
TION K
VALUA
E
BLE
AVAILA
Low-Noise Step-Up DC-DC Converters
General Description
Features
♦
90% Efficiency
♦
Adjustable Output from V
IN
to 12V
♦
1.6A, 0.21Ω, 14V Power MOSFET (MAX1790)
♦
2.4A, 0.15Ω, 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
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 0.21Ω/0.15Ω 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.
µMAX is a registered trademark of Maxim Integrated Products,
Inc.
Ordering Information
PART
MAX1790EUA
MAX1790EUA+
MAX8715EUA
MAX8715EUA+
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8 µMAX
8 µMAX
8 µMAX
8 µMAX
Applications
LCD Displays
PCMCIA Cards
Portable Applications
Hand-Held Devices
+
Denotes lead-free package.
Typical Operating Circuit
V
IN
2.6V TO 5V
Pin Configuration
TOP VIEW
COMP
IN
ON/OFF
SHDN
1
2
3
8
7
SS
FREQ
IN
LX
V
OUT
LX
FB
SHDN
MAX1790
MAX8715
FREQ
GND
MAX1790
MAX8715
6
5
GND
4
μMAX
SS
COMP
FB
________________________________________________________________
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.
Low-Noise Step-Up DC-DC Converters
MAX1790/MAX8715
ABSOLUTE MAXIMUM RATINGS
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
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
IN
=
SHDN
= 3V, FREQ = GND,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Input Supply Range
V
IN
Undervoltage Lockout
SYMBOL
V
IN
UVLO
V
IN
rising, typical hysteresis is 40mV,
LX remains off below this level
MAX1790
Quiescent Current
I
IN
MAX8715
Shutdown Supply Current
ERROR AMPLIFIER
Feedback Voltage
FB Input Bias Current
Feedback-Voltage Line
Regulation
Transconductance
Voltage Gain
OSCILLATOR
Frequency
Maximum Duty Cycle
N-CHANNEL SWITCH
Current Limit
I
LIM
V
FB
= 1V,
duty cycle =
65% (Note 1)
MAX1790
MAX8715
V
LX
= 12V
MAX1790
MAX8715
MAX1790
MAX8715
1.2
1.8
1.6
2.4
0.21
0.15
0.01
5
2.3
A
3.4
0.5
0.35
20
30
Ω
µA
f
OSC
DC
FREQ = GND
FREQ = IN
FREQ = GND
FREQ = IN
540
1000
79
640
1220
85
84
740
1500
92
kHz
%
g
m
A
V
V
FB
I
FB
Level to produce V
COMP
= 1.24V
V
FB
= 1.24V
MAX1790
MAX8715
1.222
1.24
0
125
0.05
70
70
140
160
700
1.258
40
190
0.15
240
240
V
nA
%/V
µS
V/V
I
IN
SHDN
= GND
V
FB
= 1.3V, not switching
V
FB
= 1.0V, switching
V
FB
= 1.3V, not switching
V
FB
= 1.0V, switching
CONDITIONS
MIN
2.6
2.25
2.38
0.18
2
0.21
2.5
0.1
TYP
MAX
5.5
2.52
0.35
5
0.35
5.0
10
µA
mA
UNITS
V
V
Level to produce V
COMP
= 1.24V,
2.6V < V
IN
< 5.5V
ΔI
= 5µA
MAX1790
MAX8715
On-Resistance
Leakage Current
R
ON
I
LXOFF
2
_______________________________________________________________________________________
Low-Noise Step-Up DC-DC Converters
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
Current-Sense Transresistance
SOFT-START
Reset Switch Resistance
Charge Current
CONTROL INPUTS
Input Low Voltage
Input High Voltage
Hysteresis
FREQ Pulldown Current
SHDN
Input Current
I
FREQ
I
SHDN
V
IL
V
IH
SHDN,
FREQ
SHDN,
FREQ
SHDN,
FREQ
1.8
0.7 x V
IN
0.1 x V
IN
5
0.001
9.0
1
0.3 x V
IN
V
V
V
µA
µA
V
SS
= 1.2V
1.5
4
100
7.0
Ω
µA
SYMBOL
R
CS
MAX1790
MAX8715
CONDITIONS
MIN
0.30
0.20
TYP
0.45
0.30
MAX
0.65
0.43
UNITS
V/A
MAX1790/MAX8715
ELECTRICAL CHARACTERISTICS
(V
IN
=
SHDN
= 3V, FREQ = GND,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 2)
PARAMETER
Input Supply Range
V
IN
Undervoltage Lockout
SYMBOL
V
IN
UVLO
V
IN
rising, typical hysteresis is 40mV,
LX remains off below this level
MAX1790
Quiescent Current
I
IN
MAX8715
Shutdown Supply Current
ERROR AMPLIFIER
Feedback Voltage
FB Input Bias Current
Feedback-Voltage Line
Regulation
Transconductance
OSCILLATOR
Frequency
Maximum Duty Cycle
f
OSC
DC
FREQ = GND
FREQ = IN
FREQ = GND
490
900
78
770
1500
92
kHz
%
g
m
V
FB
I
FB
Level to produce V
COMP
= 1.24V
V
FB
= 1.24V
MAX1790
MAX8715
1.215
1.24
1.260
40
190
0.15
70
70
260
260
V
nA
%/V
µS
I
IN
SHDN
= GND
V
FB
= 1.3V, not switching
V
FB
= 1.0V, switching
V
FB
= 1.3V, not switching
V
FB
= 1.0V, switching
CONDITIONS
MIN
2.6
2.25
TYP
MAX
5.5
2.52
0.35
5
0.35
5
10
µA
mA
UNITS
V
V
Level to produce V
COMP
= 1.24V,
2.6V < V
IN
< 5.5V
ΔI
= 5µA
MAX1790
MAX8715
_______________________________________________________________________________________
3
Low-Noise Step-Up DC-DC Converters
MAX1790/MAX8715
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
=
SHDN
= 3V, FREQ = GND,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 2)
PARAMETER
N-CHANNEL SWITCH
Current Limit
I
LIM
V
FB
= 1V,
duty cycle =
65% (Note 1)
MAX1790
MAX8715
MAX1790
MAX8715
SHDN,
FREQ
SHDN,
FREQ
0.7 x V
IN
0.30
0.20
MAX1790
MAX8715
1.2
1.8
2.3
A
3.0
0.5
0.35
0.65
0.43
0.3 x V
IN
Ω
V/A
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
On-Resistance
Current-Sense Transresistance
CONTROL INPUTS
Input Low Voltage
Input High Voltage
R
ON
R
CS
V
IL
V
IH
V
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.
4
_______________________________________________________________________________________
Low-Noise Step-Up DC-DC Converters
MAX1790/MAX8715
Typical Operating Characteristics
(Circuit of Figure 1, V
IN
= 3.3V, f
OSC
= 640kHz, T
A
= +25°C, unless otherwise noted.)
MAX1790 EFFICIENCY
vs. OUTPUT CURRENT
MAX1790 toc01
MAX1790 EFFICIENCY
vs. OUTPUT CURRENT
MAX1790 toc02
MAX1790 EFFICIENCY
vs. OUTPUT CURRENT
90
85
EFFICIENCY (%)
80
75
70
65
60
f
OSC
= 640kHz
L = 10μH
f
OSC
= 1.2MHz
L = 5.4μH
MAX1790 toc03
95
90
85
EFFICIENCY (%)
80
75
70
65
60
55
50
1
10
100
V
IN
= 3.3V
V
OUT
= 5V
f
OSC
= 1.2MHz
L = 2.7μH
f
OSC
= 640kHz
L = 5.4μH
95
90
85
EFFICIENCY (%)
80
75
70
65
60
55
50
V
IN
= 3.3V
V
OUT
= 12V
1
10
100
f
OSC
= 640kHz
L = 10μH
f
OSC
= 1.2MHz
L = 5.4μH
95
55
50
1
10
100
OUTPUT CURRENT (mA)
V
IN
= 5V
V
OUT
= 12V
1000
1000
1000
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
NO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX1790 toc04
MAX1790 OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX1790 toc05
MAX8715 EFFICIENCY
vs. OUTPUT CURRENT
90
85
EFFICIENCY (%)
80
75
70
65
60
55
V
IN
= 3.3V
1
10
100
1000
V
IN
= 5.0V
V
OUT
= 9V
f
OSC
= 1.2MHz
L = 6.8μH
MAX1790 toc06
0.7
NO-LOAD SUPPLY CURRENT (mA)
0.6
0.5
0.4
0.3
0.2
0.1
0
2.5
3.0
3.5
4.0
4.5
INPUT VOLTAGE (V)
V
OUT
= 12V
5.0
f
OSC
= 1.2MHz
f
OSC
= 640kHz
12.10
12.05
12.00
OUTPUT VOLTAGE (V)
11.95
11.90
11.85
11.80
11.75
11.70
11.65
11.60
f
OSC
= 640kHz
0
T
A
= +25°C
T
A
= -40°C
T
A
= +85°C
95
50
45
5.5
20 40 60 80 100 120 140 160 180 200
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
_______________________________________________________________________________________
5
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