MAX1831 데이터 시트보기 (PDF) - Maxim Integrated
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MAX1831 Datasheet PDF : 13 Pages
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3A, 1MHz, Low-Voltage, Step-Down Regulators with
Synchronous Rectification and Internal Switches
INPUT
CIN
10Ω
22µF,
6.3V X5R
2.2µF
470pF
RTOFF
IN
LX
MAX1830 FB
MAX1831
VCC
PGND
SHDN
COMP
GND
FBSEL
REF
TOFF
L
1.5µF
SUMIDA
CDRH-6D28
OUTPUT
COUT
120µF, 4V
Panasonic SP
MAX1830
MAX1831
VOUT = 2.5V, FBSEL = VCC
VOUT = 2.5V, FBSEL = VCC
1µF VOUT = 1.8V, FBSEL = REF
VOUT = 3.3V, FBSEL = REF
VOUT = 1.5V, FBSEL = FLOATING VOUT = 1.5V, FBSEL = FLOATING
Figure 1. Typical Circuit
470pF
COMP
REF
10Ω
VIN
VCC
2.2µF
SHDN
FBSEL
FB
FEEDBACK
SELECTION
Gm
MAX1830
MAX1831
DIGITAL
SOFT-START
IN
CURRENT
SENSE
SKIP
REF
PWM LOGIC
AND
DRIVERS
SUMMING
COMPARATOR
LX
CIN
CERAMIC
VIN
3.0V TO 5.5V
COUT
VOUT
REF
1µF
REF
GND
TIMER
CURRENT
SENSE
TOFF
RTOFF
PGND
NOTE: HEAVY LINES DENOTE HIGH-CURRENT PATHS.
Figure 2. Functional Diagram
lation comparator turns the PMOS switch on at the end
of each off-time, keeping the device in continuous-con-
duction mode. The PMOS switch remains on until the
output is in regulation or the current limit is reached.
When the PMOS switch turns off, it remains off for the
programmed off-time (tOFF). To control the current
under short-circuit conditions, the PMOS switch
remains off for approximately 4 x tOFF when VOUT <
VOUT(NOM) / 4.
Idle Mode
Under light loads, the devices improve efficiency by
switching to a pulse-skipping Idle Mode. Idle Mode
operation occurs when the current through the PMOS
switch is less than the Idle Mode threshold current. Idle
Mode forces the PMOS to remain on until the current
through the switch reaches the Idle Mode threshold,
thus minimizing the unnecessary switching that
degrades efficiency under light loads. In Idle Mode, the
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