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MAX8575
User Manual
10 pgs662.61 Kb0

Rainbow Electronics MAX8575 User Manual

General Description
The MAX8570 family of LCD step-up converters uses an internal n-channel switch and an internal p-channel output isolation switch. These converters operate from a 2.7V to 5.5V supply voltage and deliver up to 28V at the output.
A unique control scheme provides the highest efficien­cy over a wide range of load conditions. The internal MOSFET switch reduces external component count and a high switching frequency (up to 800kHz) allows for tiny surface-mount components. Three current-limit options are available. The MAX8570 and MAX8572 use a 110mA current limit to reduce ripple and component size in low-current applications. For high-power require­ments, the MAX8574 and MAX8575 use a 500mA cur­rent limit and supply up to 20mA at 20V. The MAX8571 and MAX8573 use a 250mA current limit for a compro­mise between ripple and power. Built-in safety features protect the internal switch and down-stream compo­nents from fault conditions.
Additional features include a low quiescent current and a True Shutdownmode to save power. The MAX8570/ MAX8571/MAX8574 allow the user to set the output voltage between 3V and 28V, and the MAX8572/ MAX8573/MAX8575 have a preset 15V output. These step-up converters are ideal for small LCD panels with low current requirements, but can also be used in other applications. The MAX8571 evaluation kit is available to help reduce design time.
Applications
LCD Bias Generators
Polymer LEDs (OLED)
Cellular or Cordless Phones
Palmtop Computers
Personal Digital Assistants (PDAs)
Organizers
Handy Terminals
Features
♦ 15V or Adjustable Output Voltage Up to 28V
♦ Safety Features Protect Against Output Faults
♦ 20mA at 20V from a Single Li+ Battery
♦ True Shutdown
♦ 87% Efficiency
♦ Up to 800kHz Switching Frequency
♦ Small 6-Pin SOT23 Package
MAX8570–MAX8575
High-Efficiency LCD Boost
with True Shutdown
________________________________________________________________ Maxim Integrated Products 1
Ordering Information
19-3329; Rev 0; 7/04
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-
TOP
MARK
MAX8570EUT-T*
6 SOT23-6
ABTJ
MAX8571EUT-T*
6 SOT23-6
ABTK
MAX8572EUT-T
6 SOT23-6
ABTL
MAX8573EUT-T
6 SOT23-6
ABTM
MAX8574EUT-T*
6 SOT23-6
ABTN
MAX8575EUT-T
6 SOT23-6
ABTO
GND
LX
16V
CC
5SW
FB
MAX8570 MAX8571 MAX8574
SOT23-6
TOP VIEW
2
34SHDN
GND
LX
16V
CC
5SW
OUT
MAX8572 MAX8573 MAX8575
SOT23-6
2
34SHDN
Pin Configurations
PART
OUTPUT VOLTAGE
MAX8570EUT 110mA Adjustable
MAX8571EUT 250mA Adjustable
MAX8572EUT 110mA 15V
MAX8573EUT 250mA 15V
MAX8574EUT 500mA Adjustable
MAX8575EUT 500mA 15V
Selector Guide
True Shutdown is a trademark of Maxim Integrated Products, Inc.
MAX8572 MAX8573 MAX8575
SW
V
CC
LX
OUT
GND
ON
OFF
V
CC
= 2.7V TO 5.5V
V
OUT
= VCC TO 28V
SHDN
Typical Operating Circuit
*Future products—contact factory for availability.
PACKAGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
CURRENT LIMIT
MAX8570–MAX8575
High-Efficiency LCD Boost with True Shutdown
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC= V
SHDN
= 3.6V, SW floating, VFB= 1.3V (MAX8570/MAX8571/MAX8574) or V
OUT
= 16V (MAX8572/MAX8573/MAX8575), TA=
-40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
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.
VCC, SHDN to GND..................................................-0.3V to +6V
SW to GND .................................................-0.3V to (V
CC
+ 0.3V)
FB to GND (MAX8570/MAX8571/
MAX8574)...............................................-0.3V to (V
CC
+ 0.3V)
OUT to GND (MAX8572/MAX8573/MAX8575) .......-0.3V to +30V
LX to GND ..............................................................-0.3V to +30V
I
LX
, ICC..............................................................................600mA
Continuous Power Dissipation (T
A
= +70°C)
SOT23-6 (derate 8.7 mW/°C above +70°C).............695.7 mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER CONDITIONS
UNITS
VCC Input Voltage Range
V
VCC Undervoltage Lockout VCC rising, 50mV typical hysteresis
2.5
V
VCC Supply Current 25 35 µA
TA = +25°C
1
VCC Shutdown Current SHDN = GND, VCC = 5.5V
µA
Line Regulation
Circuit of Figure 3, V
OUT
= 15V, I
LOAD
= 5mA,
V
CC
= 2.7V to 5.5V
0.1 %/V
Load Regulation Circuit of Figure 3, V
OUT
= 15V, I
LOAD
= 0 to 5mA 0.1
%/mA
TA = 0°C to +85°C
FB Regulation Voltage
T
A
= -40°C to +85°C
V
FB Input Bias Current -50 -4
nA
TA = 0°C to +85°C
15
OUT Regulation Voltage
T
A
= -40°C to +85°C
V
OUT Input Bias Current V
OUT
= 15V 2.4 4.4 µA
LX Voltage Range 28 V
MAX8571/MAX8573
MAX8570/MAX8572
LX Switch Current Limit (Note 2)
MAX8574/MAX8575
A
MAX8571/MAX8573/MAX8574/MAX8575, I
LX
= 100mA 0.9 1.5
LX On-Resistance
MAX8570/MAX8572, I
LX
= 50mA 1.5 2.4
Ω
TA = +25°C
2
LX Leakage Current V
LX
= 28V
µA
Maximum LX On-Time 81114µs
VFB > 1V or V
OUT
> 12.2V 0.8 1 1.2
Minimum LX Off-Time
V
FB
= 0.25V or V
OUT
= 3.4V 4.0 5 6.0
µs
Current-Limit Propagation Delay
55 ns
SHDN Low Level (VIL)2.7V ≤ VCC ≤ 5.5V 0.7 V
4.2V ≤ VCC ≤ 5.5V 1.5
SHDN High Level (VIH)
2.7V ≤ V
CC
< 4.2V 1.4
V
SHDN Leakage Current -1 +1 µA
MIN TYP MAX
2.70 5.50
2.33
2.65
TA = -40°C to +85°C 0.05
TA = -40°C to +85°C 0.05
1.216 1.226 1.236
1.2137 1.2383
14.85
14.813 15.187
0.217 0.241 0.267
0.088 0.101 0.108
0.425 0.484 0.540
0.05
0.01
+50
15.15
MAX8570–MAX8575
High-Efficiency LCD Boost
with True Shutdown
_______________________________________________________________________________________ 3
EFFICIENCY vs. SUPPLY VOLTAGE
MAX8570/71/73/74/75 toc06
SUPPLY VOLTAGE (V)
EFFICIENCY (%)
5.14.74.33.93.53.1
75
80
85
90
95
100
70
2.7 5.5
L1 = TOKO A914BYW-470M
47µH, 1mA LOAD
47µH, 5mA LOAD
L1 = MURATA LQH32CN220K23
22µH, 5mA LOAD
22µH, 1mA LOAD
Typical Operating Characteristics
(MAX8571, VCC= 3.6V, V
OUT
= 18V, Circuit of Figure 2, TA= +25°C, unless otherwise noted.)
OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE (MAX8571)
MAX8570/71/73/74/75 toc01
SUPPLY VOLTAGE (V)
OUTPUT VOLTAGE (V)
5.14.73.9 4.33.53.1
17.6
17.7
17.8
17.9
18.0
18.1
18.2
18.3
18.4
18.5
17.5
2.7 5.5
L1 = MURATA LQH32CN220K23 R1 = 3.9MΩ, R2 = 287kΩ
5mA LOAD
1mA LOAD
OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE (FIGURE 3, MAX8573)
MAX8570/71/73/74/75 toc02
SUPPLY VOLTAGE (V)
OUTPUT VOLTAGE (V)
5.14.73.9 4.33.53.1
14.6
14.7
14.8
14.9
15.0
15.1
15.2
15.3
15.4
15.5
14.5
2.7 5.5
L1 = MURATA LQH32CN220K23
5mA LOAD
1mA LOAD
OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE (MAX8574)
MAX8570/71/73/74/75 toc03
SUPPLY VOLTAGE (V)
OUTPUT VOLTAGE (V)
4.64.34.03.73.4
17.2
18.2
18.0
17.8
17.6
17.4
18.4
18.6
18.8
19.0
17.0
3.1 4.9
L1 = TOKO S1024-100M R1 = 1.1MΩ, R2 = 75kΩ, C4 = 4.7pF
5mA LOAD
20mA LOAD
OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX8570/71/73/74/75 toc04
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
20155 10
17.6
17.8
18.0
18.2
18.4
18.6
18.8
19.0
17.4 025
L1 = MURATA LQH32CN220K23
R1 = 3.9MΩ, R2 = 287kΩ, C4 = 10pF
MAX8570 MAX8571
MAX8574, R1 = 1.1MΩ, R2 = 75kΩ, C4 = 4.7pF
OUTPUT VOLTAGE vs. TEMPERATURE
MAX8570/71/73/74/75 toc05
TEMPERATURE (°C)
OUTPUT VOLTAGE (V)
603510-15
17.7
17.8
17.9
18.0
18.1
18.2
18.3
18.4
17.6
-40 85
1mA LOAD
Note 1: Parameters are production tested at TA= +25°C. Limits over temperature are guaranteed by design. Note 2: Specified currents are measured at DC. Actual LX current limits are slightly higher in circuit due to current-limit comparator
delay. Actual currents (with 2µH) are 110mA (MAX8570/MAX8572), 250mA (MAX8571/MAX8573), and 500mA (MAX8574/MAX8575).
ELECTRICAL CHARACTERISTICS (continued)
(VCC= V
SHDN
= 3.6V, SW floating, VFB= 1.3V (MAX8570/MAX8571/MAX8574) or V
OUT
= 16V (MAX8572/MAX8573/MAX8575), TA=
-40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER CONDITIONS
MIN
TYP
MAX
UNITS
VCC = 3.6V, VSW = 0V, VFB = 0V, ICC (peak)
SW PMOS Current Limit
V
CC
= 3.6V, VSW = 0V, VFB = 0V, ICC (average)
A
SW PMOS On-Resistance VCC = 2.7V, VFB = 0V, I
SW
= 100mA 1.5 2.5 Ω
TA = +25°C
1
SW PMOS Leakage Current
µA
SW Soft-Start Time VCC = 2.7V, CSW = 4.7µF 0.2 1 ms
0.45 0.75 1.10
0.15 0.30 0.60
SW = GND, VCC = 5.5V, VFB = 0V
= -40°C to +85°C 0.02
T
A
0.01
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