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PDF MAX618 Data sheet ( Hoja de datos )
| Número de pieza | MAX618 | |
| Descripción | 28V / PWM / Step-Up DC-DC Converter | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MAX618 (archivo pdf) en la parte inferior de esta página. Total 14 Páginas | ||
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19-1462; Rev 0; 6/99
28V,EVFAOLLULAOTWIOSNDKAITTAMSAHNEUEATL PWM, Step-Up DC-DC Converter
General Description
The MAX618 CMOS, PWM, step-up DC-DC converter
generates output voltages up to 28V and accepts
inputs from +3V to +28V. An internal 2A, 0.3Ω switch
eliminates the need for external power MOSFETs while
supplying output currents up to 500mA or more. A
PWM control scheme combined with Idle Mode™ oper-
ation at light loads minimizes noise and ripple while
maximizing efficiency over a wide load range. No-load
operating current is 500µA, which allows efficiency up
to 93%.
A fast 250kHz switching frequency allows the use of
small surface-mount inductors and capacitors. A shut-
down mode extends battery life when the device is not
in use. Adaptive slope compensation allows the
MAX618 to accommodate a wide range of input and
output voltages with a simple, single compensation
capacitor.
The MAX618 is available in a thermally enhanced 16-
pin QSOP package that is the same size as an industry-
standard 8-pin SO but dissipates up to 1W. An
evaluation kit (MAX618EVKIT) is available to help
speed designs.
Features
o Adjustable Output Voltage Up to +28V
o Up to 93% Efficiency
o Wide Input Voltage Range (+3V to +28V)
o Up to 500mA Output Current at +12V
o 500µA Quiescent Supply Current
o 3µA Shutdown Current
o 250kHz Switching Frequency
o Small 1W 16-Pin QSOP Package
PART
MAX618EEE
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
16 QSOP
Applications
Automotive-Powered DC-DC Converters
Industrial +24V and +28V Systems
LCD Displays
Palmtop Computers
Typical Operating Circuit
Pin Configuration
TOP VIEW
GND 1
LX 2
LX 3
LX 4
SHDN 5
COMP 6
FB 7
GND 8
MAX618
16 GND
15 PGND
14 PGND
13 PGND
12 GND
11 VL
10 IN
9 GND
VIN
3V TO 28V
IN LX
MAX618
SHDN
PGND
VL FB
COMP
GND
VOUT
UP TO 28V
QSOP
Idle Mode is a trademark of Maxim Integrated Products.
________________________________________________________________ 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 1-800-835-8769.
1 page  
28V, PWM, Step-Up DC-DC Converter
Pin Description
PIN
1, 8, 9,
12, 16
2, 3, 4
5
NAME
GND
LX
SHDN
6 COMP
7 FB
10 IN
11
13, 14, 15
VL
PGND
FUNCTION
Ground
Drain of internal N-channel switch. Connect the inductor between IN and LX.
Shutdown Input. A logic low puts the MAX618 in shutdown mode and reduces supply current to 3µA.
SHDN must not exceed VL. In shutdown, the output falls to VIN less one diode drop.
Compensation Input. Bypass to GND with the capacitance value shown in Table 2.
Feedback Input. Connect a resistor-divider network to set VOUT. FB threshold is 1.5V.
LDO Regulator Supply Input. IN accepts inputs up to +28V. Bypass to GND with a 1µF ceramic capacitor
as close to pins 10 and 12 as possible.
Internal 3.1V LDO Regulator Output. Bypass to GND with a 4.7µF capacitor.
Power Ground, source of internal N-channel switch
3V TO 28V
VIN
CIND
1µF
L
IN LX
MAX618
SHDN
PGND
ECB1Q503L
VOUT
UP TO 28V
COUT
R1
4.7µF
CCOMP
VL FB
CP R2
COMP
GND
VOUT
R1
R2 CIND
8V 402kΩ 93.1kΩ 150µF
12V 715kΩ 100kΩ 100µF
28V 574kΩ 32.4kΩ 86µF
L
12µH
15µH
39µH
COUT
150µF
100µH
33µF
CP
220pF
56pF
47pF
CCOMP
0.082µF
0.1µF
0.47µF
Figure 1. Single-Supply Operation
_______________ Detailed Description
The MAX618 pulse-width modulation (PWM) DC-DC
converter with an internal 28V switch operates in a wide
range of DC-DC conversion applications including
boost, SEPIC, and flyback configurations. The MAX618
uses fixed-frequency PWM operation and Maxim’s pro-
prietary Idle Mode control to optimize efficiency over a
wide range of loads. It also features a shutdown mode
to minimize quiescent current when not in operation.
PWM Control Scheme and
Idle Mode Operation
The MAX618 combines continuous-conduction PWM
operation at medium to high loads and Idle Mode oper-
ation at light loads to provide high efficiency over a
wide range of load conditions. The MAX618 control
scheme actively monitors the output current and auto-
matically switches between PWM and Idle Mode to
optimize efficiency and load regulation. Figure 2 shows
a functional diagram of the MAX618’s control scheme.
The MAX618 normally operates in low-noise, continu-
ous-conduction PWM mode, switching at 250kHz. In
PWM mode, the internal MOSFET switch turns on with
each clock pulse. It remains on until either the error
comparator trips or the inductor current reaches the 2A
switch-current limit. The error comparator compares the
feedback-error signal, current-sense signal, and slope-
compensation signal in one circuit block. When the
switch turns off, energy transfers from the inductor to
_______________________________________________________________________________________________________ 5
5 Page 
28V, PWM, Step-Up DC-DC Converter
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet MAX618.PDF ] | |
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