MAX1945REUI Maxim Integrated Products, MAX1945REUI Datasheet - Page 16

• Manufacturer Part Number: MAX1945REUI
• Description: DC/DC Switching Regulators 1MHz 1% 6A Step-Down PWM
• Manufacturer: Maxim Integrated Products

Specifications of MAX1945REUI

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

mum zero-crossing frequency should be less than one-
third of the load-impedance zero frequency, fz
previous requirement on the ESR zero frequency
applies to ceramic output capacitors.
The loop-gain equation at unity-gain frequency, f
given by:
where G
transconductance of the voltage error amplifier.
Calculate R
Set the error-amplifier compensation zero formed by R
and C
f
1MHz, 1% Accurate, 6A Internal Switch
Step-Down Regulators
Table 3. Compensation Values for Output Voltages (1MHz)
Figure 1. Typical Application Circuit (Fixed Output Voltage)
16
PLOAD
2.6V TO 5.5V
R
______________________________________________________________________________________
G
C
INPUT:
100µF
VOUT (V)
C
R
C
EA(fc)
C
= (V
, at maximum load. Calculate C
C
8V
C
IN
(10%)
equal to the load-impedance pole frequency,
C
(1%)
EA(fc)
C
OUT
C
✕
as:
G
R
R
C
✕
IN
C
= gm
DC
C
f
C
= (C
)/(gm
✕
IN
V
V
CTL1
CTL2
COMP
FBSEL
BAT54A
DD
CC
SYNC
(f
EA
PLOAD
MAX1945R
MAX1945S
OUT
EA
✕
BST
100kΩ
330pF
GND
0.8
R
✕
SYNCOUT
✕
C
/f
V
R
0.1µF
PGND
10V
C
, and gm
FB
REF
OUT
LX
FB
)
✕
✕
✕
(V
)/R
180µF
G
FB
C
C
0.22µF
10V
DC
4V
1µH
/V
as follows:
EA
OUT
✕
f
= 50µ, the
PLOAD
100kΩ
330pF
) = 1
ESR
1.2
OUTPUT:
1.8V, 6A
. The
C
)
, is
C
As the load current decreases, the load-impedance
pole also decreases; however, the switching regulator
DC gain increases accordingly, resulting in a constant
closed-loop unity-gain frequency. Table 3 shows the
values for R
values are based on 2
0.68µH output inductance.
For C
accordingly when using large values of C
V
I
C
R
gm
gmc = 18.2s
f
R
fp
94
Figure 2. Typical Application Circuit (Adjustable Output
Voltage)
OUT(MAX)
SWITCH
OUT
ESR
OUT
OUT
DC
2.6V TO 5.5V
✕
EA
178kΩ
100pF
10
= [1/(2π
= 0.005Ω
INPUT:
100µF
1.8
OUT
= 1.8V
= V
= 2
= 50µ
-6 ✕
8V
C
IN
= 1.0MHz
C
OUT
C
✕
= 6A
= 2
(0.3 + 0.005))] = 5.554kHz
47µF
C
/I
✕
and C
OUT(MAX)
R
✕
IN
R
Applications Information
C
C
47µF and L = 0.68µH. Decrease R
OUT
IN
V
V
CTL1
CTL2
COMP
BAT54A
DD
C
CC
SYNC
✕
at various output voltages. The
✕
178kΩ
MAX1945R
MAX1945S
100pF
= 1.8V/6A= 0.3Ω
(R
2.2
47µF output capacitors and a
BST
GND
OUT
SYNCOUT
FBSEL
0.1µF
PGND
10V
REF
+ R
LX
FB
ESR
180µF
0.22µF
10V
4V
))] = [1/(2
1µH
OUT
249kΩ
100pF
3.3
or L.
R1
R2
V
OUT
✕
π
C
✕