MAX1637 Datasheet, PDF (19/20 Pages) Maxim Integrated Products – Miniature, Low-Voltage, Precision Step-Down Controller

Miniature, Low-Voltage,
Precision Step-Down Controller
20Ω
V_BIAS 3.15V TO 5.5V
4.7µF
TANTALUM
1µF
V_CC
V_GG
SYNC
CMPSH-3
SKIP
BST
0.1µF
MAX1637 _DH
SHDN
ON/OFF
LX
DL
PGND
IRF7401
220µF
OS-CON
IRF7401
10µH
CDHR125-100
MBRS130
20mΩ
1%
CSH
REF
CSL
1µF
GND CC FB
470pF
OUTPUT = 2.5V AT 4A
470µF
LOW ESR
130k
TANTALUM
1%
100k
1%
Figure 7. 3.15V to 5.5V Single-Supply Application Circuit
sensing at the supply’s output terminals without interfer-
ence from IR drops and ground noise. Other high-cur-
rent paths should also be minimized, but focusing
primarily on short ground and current-sense connec-
tions eliminates about 90% of all PC board layout prob-
lems (see the PC board layouts in the MAX1637
evaluation kit manual for examples).
2) Place the IC and signal components. Keep the main
switching nodes (LX nodes) away from sensitive
analog components (current-sense traces and REF
capacitor). Place the IC and analog components on
the opposite side of the board from the power-
switching node. Important: The IC must be no fur-
ther than 10mm from the current-sense resistors.
Keep the gate-drive traces (DH, DL, and BST) short-
er than 20mm and route them away from CSH, CSL,
and REF. Place ceramic bypass capacitors close to
the IC. The bulk capacitors can be placed further
away.
3) Use a single-point star ground where the input
ground trace, power ground (subground plane), and
HIGH-CURRENT PATH
SENSE RESISTOR
MAX1637
Figure 8. Kelvin Connections for the Current-Sense Resistors
normal ground plane meet at the supply's output
ground terminal. Connect both IC ground pins and
all IC bypass capacitors to the normal ground plane.
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