MAX618EEE(1999) 查看數據表（PDF） - Maxim Integrated
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MAX618EEE Datasheet PDF : 14 Pages
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28V, PWM, Step-Up DC-DC Converter
VL can be overdriven by an external supply between
2.7V and 5.5V. In systems with +3.3V or +5V logic
power supplies available, improve efficiency by power-
ing VL and VIN directly from the logic supply as shown
in Figure 3.
Operating Configurations
The MAX618 can be connected in one of three configura-
tions described in Table 2 and shown in Figures 1, 3, and
4. The VL linear regulator allows operation from a single
supply between +3V and +28V as shown in Figure 1.
The circuit in Figure 3 allows a logic supply to power
the MAX618 while using a separate source for DC-DC
conversion power (inductor voltage). The logic supply
(between 2.7V and 5.5V) connects to VL and IN. VL =
IN; voltages of 3.3V or more improve efficiency by pro-
viding greater gate drive for the internal MOSFET.
The circuit in Figure 4 allows separate supplies to
power IN and the inductor voltage. It differs from the
connection in Figure 3 in that the MAX618 chip supply
is not limited to 5.5V.
Table 2. Input Configurations
CIRCUIT
Figure 1
Figure 3
Figure 4
CONNECTION
VIN
RANGE
Input voltage connects 3V to VOUT
to IN and inductor.
(up to 28V)
IN and VL connect
together. Inductor volt-
age supplied by a
separate source.
2.7V to 5.5V
IN and inductor volt-
age supplied by sepa-
rate sources.
3V to 28V
INDUCTOR
VOLTAGE
BENEFITS/COMMENTS
• Single-supply operation.
VIN
• SHDN must be connected to or pulled up to VL. On/off
control requires an open-drain or open-collector connection
to SHDN.
0 to VOUT
(up to 28V)
• Increased efficiency.
• SHDN can be driven by logic powered from the supply con-
nected to IN and VL, or can be connected to or pulled up to
VL.
• Input power source (inductor voltage) is separate from the
MAX618’s bias (VIN = VL) and can be less than or greater
than VIN.
0 to VOUT
(up to 28V)
• Input power source (inductor voltage) is separate from the
MAX618’s bias (VIN) and can be less than or greater than
VIN.
• SHDN must be connected to or pulled up to VL. On/off
control requires an open-drain or open-collector connection
to SHDN.
VIND
UP TO 28V
CIND
IN
2.7V TO 5.5V
1µF
4.7µF
CCOMP
L
IN
LX
MAX618
COUT
SHDN
PGND
VL
FB
COMP
CP
GND
OUT
UP TO 28V
R1
R2
VIND
UP TO 28V
IN
3V TO 28V
1µF
L
CIND
IN
LX
MAX618
SHDN
PGND
VL
4.7µF
FB
CCOMP
COMP
GND
OUT
UP TO 28V
COUT
R1
CP
R2
Figure 3. Dual-Supply Operation (VIN = 2.7V to 5.5V)
Figure 4. Dual-Supply Operation (VIN = 3V to 28V)
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