MAX1945SEUI Maxim Integrated Products, MAX1945SEUI Datasheet - Page 17

• Manufacturer Part Number: MAX1945SEUI
• Description: DC/DC Switching Regulators 1MHz 1% 6A Step-Down PWM
• Manufacturer: Maxim Integrated Products

Specifications of MAX1945SEUI

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

fz
0.005)] = 339kHz.
For a 0.68µH output inductor, choose the closed-loop
unity-gain crossover frequency (f
Determine the switching regulator DC gain:
then:
Output Inductor: 0.68µH/12A, 5mΩ ESR (max), Coilcraft
DO3316P-681HC
Output Capacitor C5: 2XJMK432BJ476MM
Input Capacitor C1: LMK432BJ226MM
Figure 3. Typical Application Circuit with all ceramic capacitors
(1MHz)
C
ESR
(1.8
C
R
3 x 22µF
= (C
C
V
GND
CC
C1
= [1/(2π
= (V
✕
= 3.3V OR 5V
V
G
120kHz)/(50
OUT
IN
0.1µF
= 2.5V
DC
10Ω
OUT
1µF
C6
R1
C4
✕
= gmc
C
100pF
178kΩ
C
R
choose C
✕
✕
R
OUT
C
f
C
C
______________________________________________________________________________________
OUT
)/(gm
IN
IN
IN
IN
V
V
CTL1
CTL2
SYNCOUT
SYNC
COMP
1MHz, 1% Accurate, 6A Internal Switch
)/R
✕
DD
CC
✕
178kΩ (1%)
R
10
C
R
OUT
MAX1945R
MAX1945S
EA
C
ESR
-6 ✕
=(94µF
= 100pF, 10%
✕
= 18.2
)] = [1/(2
V
0.8
FB
FBSEL
BST
✕
✕
REF
LX
LX
LX
LX
LX
LX
LX
LX
FB
✕
5.46
0.3)/178kΩ ≈ 156pF,
✕
G
0.3 = 5.46
DC
✕
D1
C3
0.1µF
c
✕
0.68µF
✕
π
) at 120kHz.
L1
0.22µF
5.554kHz) ≈
fp
2 x 47µF
✕
C4
LOAD
94
C5
✕
1.8V, 6A
10
PGND
) =
-6 ✕
Careful PC board layout is critical to achieve clean and
stable operation. The switching power stage requires
particular attention. Follow these guidelines for good
PC board layout:
1) Place decoupling capacitors as close to the IC as
2) Connect input and output capacitors to the power
3) Keep the high-current paths as short and wide as
4) Connect IN, LX, and PGND separately to a large
5) Ensure all feedback connections are short and
6) Route high-speed switching nodes away from sen-
TRANSISTOR COUNT: 5000
PROCESS: BiCMOS
Step-Down Regulators
possible. Keep power ground plane (connected to
PGND) and signal ground plane (connected to
GND) separate. Star connect both ground plane at
output capacitor.
ground plane; connect all other capacitors to the
signal ground plane.
possible. Keep the path of switching current short
and minimize the loop area formed by the high-side
MOSFET, the low side MOSFET, and the input
capacitors. Avoid vias in the switching paths.
copper area to help cool the IC to further improve
efficiency and long-term reliability.
direct. Place the feedback resistors as close to the
IC as possible.
sitive analog areas (FB, COMP).
Chip Information
PC Board Layout
Considerations
17