MAX16909_12 Datasheet, PDF (16/18 Pages) Maxim Integrated Products – 36V, 220kHz to 1MHz Step-Down Converter with Low Operating Current

MAX16909
36V, 220kHz to 1MHz Step-Down Converter
with Low Operating Current
VBAT
C1
47µF
C2
4.7µF
C3
4.7µF
C4
0.1µF
C₅
0.1µF
C_COMP1
821pF
RCOMP
9.1kI
CCOMP2
12pF
SUP
EN
FSYNC
SUPSW
BST
LX
COMP _MAX16909
OUT
R_FOSC
62kI
FOSC
FB
C_BIAS
1µF
BIAS
PGOOD
GND
C_BST
0.1µF
VOUT
R1
80.6kI
L1
15µH
D1
VOUT
1.8V AT 3A
COUT
100µF
R2
100kI
VBIAS
RPGOOD
10kI
POWER GOOD
Figure 4. 1.8V/3A Configuration
PCB Layout Guidelines
Careful PCB layout is critical to achieve low switching
losses and clean, stable operation. Use a multilayer
board whenever possible for better noise immunity and
power dissipation. Follow these guidelines for good PCB
layout:
1) Use a large contiguous copper plane under the IC
package. Ensure that all heat-dissipating components
have adequate cooling. The bottom pad of the device
must be soldered down to this copper plane for effec-
tive heat dissipation and for getting the full power out
of the IC. Use multiple vias or a single large via in this
plane for heat dissipation.
2) Isolate the power components and high-current path
from the sensitive analog circuitry. This is essential to
prevent any noise coupling into the analog signals.
3) Keep the high-current paths short, especially at the
ground terminals. This practice is essential for stable,
jitter-free operation. The high-current path composed
of input capacitor, high-side FET, inductor, and output
capacitor should be as short as possible.
4) Keep the power traces and load connections short.
This practice is essential for high efficiency. Use
thick copper PCBs (2oz vs. 1oz) to enhance full-load
efficiency.
5) The analog signal lines should be routed away from
the high-frequency planes. This ensures integrity of
sensitive signals feeding back into the IC.
6) The ground connection for the analog and power
section should be close to the IC. This keeps the
ground current loops to a minimum. In cases where
only one ground is used, enough isolation between
analog return signals and high-power signals must
be maintained.
Maxim Integrated
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