MAX1837(2002) 데이터 시트보기 (PDF) - Maxim Integrated
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MAX1837 Datasheet PDF : 13 Pages
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24V Internal Switch, 100% Duty Cycle,
Step-Down Converters
Pin Description
PIN NAME
FUNCTION
Dual-Mode Feedback Input. Connect to GND for the preset 3.3V (MAX183_EUT33) or 5.0V (MAX183_EUT50)
1
FB
output. Connect to a resistive divider between the output and FB to adjust the output voltage between 1.25V
and VIN, and connect the OUT pin to GND. When setting output voltages above 5.5V, permanently connect
SHDN to IN.
2
GND Ground
3
IN
Input Voltage. 4.5V to 24V input range. Connected to the internal P-channel power MOSFET’s source.
4
LX
Inductor Connection. Connected to the internal P-channel power MOSFET’s drain.
Shutdown Input. A logic low shuts down the MAX1836/MAX1837 and reduces supply current to 3µA. LX is
5
SHDN high impedance in shutdown. Connect to IN for normal operation. When setting output voltages above 5.5V,
permanently connect SHDN to IN.
Regulated Output Voltage High-Impedance Sense Input. Internally connected to a resistive divider. Connect
6
OUT to the output when using the preset output voltage. Connect to GND when using an external resistive divider
to adjust the output voltage.
INPUT
4.5V OR 12V
CIN
10µF
25V
IN
LX
SHDN
OUT
MAX1836
GND
FB
L1
47µH
D1
OUTPUT
3.3V OR 5V
COUT
100µF
6.3V
INPUT
4.5V OR 12V
CIN
10µF
25V
IN
LX
SHDN
OUT
MAX1837
GND
FB
L1
22µH
D1
OUTPUT
3.3V OR 5V
COUT
150µF
6.3V
CIN = TAIYO YUDEN TMK432BJ106KM
L1 = SUMIDA CDRH5D28-470
COUT = SANYO POSCAP 6TPC100M (SMALLER CAPACITORS CAN BE USED FOR 5V)
D1 = NIHON EP05Q03L
NOTE: HIGH-CURRENT PATHS SHOWN WITH BOLD LINES.
Figure 1. Typical MAX1836 Application Circuit
CIN = TAIYO YUDEN TMK432BJ106KM
L1 = SUMIDA CDRH5D28-220
COUT = SANYO OS-CON 6SA150M (SMALLER CAPACITORS CAN BE USED FOR 5V)
D1 = NIHON ED05Q03L
NOTE: HIGH-CURRENT PATHS SHOWN WITH BOLD LINES.
Figure 2. Typical MAX1837 Application Circuit
Detailed Description
The MAX1836/MAX1837 step-down converters are
designed primarily for battery-powered devices, note-
book computers, and industrial control applications. A
unique current-limited control scheme provides high
efficiency over a wide load range. Operation up to
100% duty cycle allows the lowest possible dropout
voltage, increasing the useable supply voltage range.
Under no-load, the MAX1836/MAX1837 draw only
12µA, and in shutdown mode, they draw only 3µA to
further reduce power consumption and extend battery
life. Additionally, an internal 24V switching MOSFET,
internal current sensing, and a high switching frequen-
cy minimize PC board space and component cost.
Current-Limited Control Architecture
The MAX1836/MAX1837 use a proprietary current-limit-
ed control scheme that operates with duty cycles up to
100%. These DC-DC converters pulse as needed to
maintain regulation, resulting in a variable switching fre-
quency that increases with the load. This eliminates the
high supply currents associated with conventional con-
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