MAX17505 Datasheet, PDF (16/18 Pages) Maxim Integrated Products – Step-Down DC-DC Converter

MAX17505
4.5V-60V, 1.7A, High-Efficiency,
Synchronous Step-Down DC-DC Converter
With Internal Compensation
PCB Layout Guidelines
All connections carrying pulsed currents must be very
short and as wide as possible. The inductance of these
connections must be kept to an absolute minimum due to
the high di/dt of the currents. Since inductance of a current
carrying loop is proportional to the area enclosed by the
loop, if the loop area is made very small, inductance is
reduced. Additionally, small-current loop areas reduce
radiated EMI.
A ceramic input filter capacitor should be placed close
to the V_IN pins of the IC. This eliminates as much trace
inductance effects as possible and gives the IC a cleaner
voltage supply. A bypass capacitor for the V_CC pin also
should be placed close to the pin to reduce effects of trace
impedance.
When routing the circuitry around the IC, the analog
small-signal ground and the power ground for switching
currents must be kept separate. They should be connected
together at a point where switching activity is at a
minimum, typically the return terminal of the V_CC bypass
capacitor. This helps keep the analog ground quiet.
The ground plane should be kept continuous/unbroken
as far as possible. No trace carrying high switching
current should be placed directly over any ground plane
discontinuity.
PCB layout also affects the thermal performance of the
design. A number of thermal vias that connect to a large
ground plane should be provided under the exposed pad
of the part, for efficient heat dissipation.
For a sample layout that ensures first pass success,
refer to the MAX17505 evaluation kit layout available at
www.maximintegrated.com.
Typical Application Circuit
C2
2.2µF
EN/UVLO
RT
V_IN V_IN V_IN
BST
SYNC
MODE
V_CC
SGND
MAX17505
LX
LX
LX
FB
RESET
C5
0.1µF
L1
10µH
CF
SS
C3
5.6nF
PGND PGND PGND
f_SW = 500kHz
FIGURE 3
C1
2.2µF
VIN
(6.5V TO 60V)
VOUT
5V, 1.7A
C4
22µF
R3
178kΩ
R4
39kΩ
www.maximintegrated.com
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