MAX618 Maxim, MAX618 Datasheet - Page 8

• Manufacturer Part Number: MAX618
• Description: 28V / PWM / Step-Up DC-DC Converter
• Manufacturer: Maxim

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 V
in Figure 3.
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.
28V, PWM, Step-Up DC-DC Converter
8
Table 2. Input Configurations
Figure 3. Dual-Supply Operation (V
CIRCUIT
Figure 1
Figure 3
Figure 4
_______________________________________________________________________________________
1 F
2.7V TO 5.5V
UP TO 28V
IN
4.7 F
C
V
COMP
IND
C
Input voltage connects
to IN and inductor.
IN and VL connect
together. Inductor volt-
age supplied by a
separate source.
IN and inductor volt-
age supplied by sepa-
rate sources.
IN
IND
CONNECTION
directly from the logic supply as shown
SHDN
IN
VL
COMP
MAX618
Operating Configurations
L
PGND
GND
LX
FB
IN
= 2.7V to 5.5V)
2.7V to 5.5V
3V to V
(up to 28V)
3V to 28V
C
RANGE
OUT
C
P
V
IN
OUT
UP TO 28V
R1
OUT
R2
INDUCTOR
VOLTAGE
(up to 28V)
(up to 28V)
0 to V
0 to V
V
IN
OUT
OUT
• Single-supply operation.
• SHDN must be connected to or pulled up to VL. On/off
• Increased efficiency.
• SHDN can be driven by logic powered from the supply con-
• Input power source (inductor voltage) is separate from the
•
• SHDN must be connected to or pulled up to VL. On/off
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.
Figure 4. Dual-Supply Operation (V
control requires an open-drain or open-collector connection
to SHDN.
nected to IN and VL, or can be connected to or pulled up to
VL.
MAX618’s bias (V
than V
Input power source (inductor voltage) is separate from the
MAX618’s bias (V
V
control requires an open-drain or open-collector connection
to SHDN.
IN
3V TO 28V
C
UP TO 28V
.
4.7 F
COMP
V
IN
IND
IN
1 F
.
C
IND
SHDN
BENEFITS/COMMENTS
IN
VL
COMP
IN
IN
) and can be less than or greater than
= VL) and can be less than or greater
MAX618
L
PGND
GND
LX
FB
IN
= 3V to 28V)
C
C
P
OUT
UP TO 28V
R1
R2
OUT