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PDF MAX1817 Data sheet ( Hoja de datos )
| Número de pieza | MAX1817 | |
| Descripción | Compact / High-Efficiency / Dual-Output Step-Up DC-DC Converter | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MAX1817 (archivo pdf) en la parte inferior de esta página. Total 12 Páginas | ||
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19-1794 Rev 0; 10/00
Compact, High-Efficiency, Dual-Output
Step-Up DC-DC Converter
General Description
The MAX1817 is a compact, high-efficiency, dual-out-
put step-up converter for portable devices that pro-
vides both the main logic supply and the LCD bias. The
device operates from an input voltage of +1.5V to
+5.5V, allowing the use of 2- or 3-cell alkaline batteries,
or 1-cell lithium-ion (Li+) batteries.
The MAX1817’s main regulator supplies 125mA at
either a preset 3.3V or an adjustable 2.5V to 5.5V out-
put voltage with up to 88% efficiency. A 0.1µA shut-
down state also minimizes battery drain. The
MAX1817’s secondary step-up converter provides the
LCD bias voltage and is adjustable up to +28V.
Other features include a fast switching frequency to
reduce the size of external components and a low qui-
escent current to maximize battery life. Both outputs can
be independently shut down for improved flexibility.
The MAX1817 is supplied in a compact 10-pin µMAX
package. The MAX1817 evaluation kit (MAX1817EVKIT)
is available to speed up design.
________________________Applications
Organizers/Translators
PDAs
MP3 Players
GPS Receivers
Features
o Dual Step-Up Converter in a Tiny 10-Pin µMAX
Package
o Main Output
Up to 125mA Load Current
Fixed 3.3V or Adjustable 2.5V to 5.5V
Up to 88% Efficiency
Internal Switch
o LCD Output
Up to 28V for LCD Bias
Internal Switch
o Input Voltage Range +1.5V to +5.5V
o Minimal External Components Required
o 0.1µA Logic-Controlled Shutdown
o Low 15µA Quiescent Supply Current
PART
MAX1817EUB
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
10 µMAX
Typical Operating Circuit
+1.5V
TO +5.5V
LCD ON/OFF
LX LXLCD
ONLCD FBLCD
MAIN ON/OFF
MAX1817
ON
AGND
OUT
FB
GND
LCD
MAIN
Pin Configuration
TOP VIEW
FB 1
ON 2
ONLCD 3
FBLCD 4
AGND 5
MAX1817
µMAX
10 OUT
9 LX
8 GND
7 LXLCD
6 N.C.
________________________________________________________________ Maxim Integrated Products 1
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1 page  
Compact, High-Efficiency, Dual-Output
Step-Up DC-DC Converter
(Circuit of Figure 3, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics
MAIN OUTPUT EFFICIENCY
vs. LOAD CURRENT
95
75
90
A: VIN = 3.3V,
VOUT = 5V
B: VIN = 2.4V,
VOUT = 5V
85
70
65
60
55
50
80
75
70
0.1
C: VIN = 2.4V,
VOUT = 3.3V
D: VIN = 1.8V,
VOUT = 5V
E: VIN = 1.8V,
VOUT = 3.3V
CIRCUIT OF FIGURE 2
1 10 100
LOAD CURRENT (mA)
1000
45
40
35
30
25
0.01
NO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE (LCD OFF)
18
16
14
LCD OUTPUT EFFICIENCY
vs. LOAD CURRENT
A
CB
F ED
A: VIN = +2.4V, VLCD = 12V
B: VIN = +2.4V, VLCD = 18V
C: VIN = +2.4V, VLCD = 24V
D: VIN = +1.8V, VLCD = 12V
E: VIN = +1.8V, VLCD = 18V
F: VIN = +1.8V, VLCD = 24V
VOUT = 3.3V,
NO LOAD
0.1 1 10
LOAD CURRENT (mA)
100
450
400
350
STARTUP VOLTAGE vs. LOAD CURRENT
160
RESISTIVE LOAD
140 LCD OFF
120
100
80
60
40
20
0
1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7
STARTUP VOLTAGE (V)
NO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
VOUT = 3.3V
VLCD = 18V, NO LOAD
R1 = 1MΩ, R2 = 75kΩ
12 300
10 250
8 200
6 150
4 100
2 50
0
1.0 1.5 2.0 2.5 3.0 3.5 4.0
INPUT VOLTAGE (V)
0
0123456
INPUT VOLTAGE (V)
MAIN CONVERTER
SWITCHING WAVEFORM
MAX1817-06
LCD CONVERTER
SWITCHING WAVEFORM
MAX1817-07
AA
00
BB
CC
00
10µs/div
A: ILX, 500mA/div
B: VOUT, 50mV/div, AC-COUPLED
C: VLX, 5V/div
VIN = 2.4V, VOUT = 3.3V, ILOAD,OUT = 50mA, VONLCD = 0
4µs/div
A: ILXLCD, 500mA/div
B: VLCD, 100mV/div, AC-COUPLED
C: VLXLCD, 10V/div
VIN = 2.4V, VOUT = 3.3V, ILOAD,OUT = 0,
VLCD = 18V, ILOAD,LCD = 5mA
_______________________________________________________________________________________ 5
5 Page 
Compact, High-Efficiency, Dual-Output
Step-Up DC-DC Converter
loss in efficiency. Choose a reverse breakdown voltage
greater than the output voltage.
Input Bypass Capacitor
The input supplies high currents to the inductors and
requires local bulk bypassing close to the inductors. A
low equivalent series resistance (ESR) input capacitor
connected in parallel with the battery will reduce peak
battery currents and input-reflected noise. Battery
bypassing is especially helpful at low input voltages
and with high-impedance batteries (such as alkaline
types). Benefits include improved efficiency and lower
useful end-of-life voltage for the battery. A single 10µF
low-ESR surface-mount capacitor is sufficient for most
applications.
Output Bypass Capacitors
For most applications, use a small surface-mount 22µF
or greater ceramic capacitor on the main converter out-
put, and a 1µF or greater ceramic capacitor on the LCD
output. For small ceramic capacitors, the output ripple
voltage is dominated by the capacitance value. If tanta-
lum or electrolytic capacitors are used, the ESR of the
capacitors dominates the output ripple voltage.
Decreasing the ESR reduces the output ripple voltage
and the peak-to-peak transient voltage.
LCD Compensation
The MAX1817’s LCD step-up converter feedback
requires a small 4.7pF feed-forward capacitor for the
typical application circuit. Circuits with adjustable VOUT
(main converter) from 2.5V to 5.5V may require a larger
value LCD feed-forward capacitor to prevent multipuls-
ing of the LCD converter. Larger feed-forward capaci-
tors slightly degrade load regulation, so choose the
smallest value capacitor that provides stability.
Layout Considerations
The MAX1817’s high-frequency operation makes PC
board layout important for optimal performance. Use
separate analog and power ground planes. Connect
the two planes together at a single point as close as
possible to the IC. Use surface-mount components
where possible. If leaded components are used, mini-
mize lead lengths to reduce stray capacitance and
keep the components close to the IC to minimize trace
resistance. Where an external voltage-divider is used to
set output voltage, the traces from FB or FBLCD to the
feedback resistors should be extremely short (less than
0.2in or 5mm) to minimize coupling from LX and
LXLCD. Refer to the MAX1817 evaluation kit for a full
PC board example.
____________________Chip Information
TRANSISTOR COUNT: 2785
PROCESS: BiCMOS
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet MAX1817.PDF ] | |
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