MAX1954AEUB-T Maxim Integrated Products, MAX1954AEUB-T Datasheet - Page 15

• Manufacturer Part Number: MAX1954AEUB-T
• Description: Current Mode PWM Controllers
• Manufacturer: Maxim Integrated Products

Specifications of MAX1954AEUB-T

• Number Of Outputs: 1
• Duty Cycle (max): 93 %
• Output Voltage: 0.8 V to 4.95 V
• Output Current: 25000 mA
• Mounting Style: SMD/SMT
• Package / Case: uSOP-10
• Switching Frequency: 360 KHz
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Synchronous Pin: No
• Topology: Boost, Buck
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

output filtering. For other types of capacitors, due to the
higher capacitance and ESR, the frequency of the zero
created by the capacitance and ESR is lower than the
desired closed-loop crossover frequency. Another
compensation capacitor should be added to cancel
this zero.
The basic regulator loop can be thought of as a power
modulator, output feedback divider, and an error ampli-
fier. The power modulator has DC gain set by g
R
put capacitor (C
tance (R
power modulator:
where R
R
amplifier and R
side power MOSFET. A
which the pole and zero due to the power modulator
occur are determined as follows:
The feedback voltage-divider used has a gain of G
V
ductance error amplifier has DC gain, G
R
10M . The C
The R
set by C
zero if it occurs before crossover frequency (f
f
FB
LOAD
DS(ON)
O
pMOD
. The amplifier output resistance (R
/ V
C
, with a pole and zero pair set by R
OUT
and the C
LOAD
), where A
F
ESR
2
and R
G
, where V
f
pdEA
f
MOD
zMOD
). Below are equations that define the
C
= V
, R
DS(ON)
C
f
f
zEA
pEA
C
OUT
OUT
OUT
C
O
______________________________________________________________________________________
CS
to cancel the output-capacitor ESR
set a zero. There is an optional pole
g
, and the R
2
FB
mc
) and its equivalent series resis-
2
/ I
Controller with Foldback Current Limit
is the gain of the current-sense
2
is the on-resistance of the high-
2
OUT(MAX)
is equal to 0.8V. The transcon-
CS
C
R
R
R
R
C
C
LOAD
is 3.5. The frequencies at
LOAD
LOAD
C
LOAD
OUT
C
1
Low-Cost, Current-Mode PWM Buck
1
C
F
1
1
1
C
(
, and g
R
set a dominant pole.
O
R
R
f
f
S
f
R
S
f
C
C
S
S
ESR
R
mc
C
L
L
EA(DC)
O
LOAD
)
L
L
) is typically
= 1 / (A
C
, the out-
):
R
= g
ESR
mc
FB
CS
m
=
x
x
x
The f
tor pole f
be less than 1/8th of the switching frequency:
Therefore, the loop-gain equation at the crossover fre-
quency is:
When f
then R
where g
The error-amplifier compensation zero formed by R
and C
is calculated by:
If f
tion capacitor, C
ESR zero. C
As the load current decreases, the modulator pole also
decreases. However, the modulator gain increases
accordingly and the crossover frequency remains
the same.
When f
at f
G
EA fC
zMOD
C
( )
C
is:
C
C
zMOD
zMOD
should be much higher than the power modula-
mEA
should be set at the modulator pole f
is calculated as:
is less than 5 x f
PMOD
g
mEA
G
C
f
G
= 110µs.
is greater than f
is calculated by:
EA fC
C
is less than f
MOD fC
R
. Also, the crossover frequency should
C
( )
C
f
f
R and G
R
f
pMOD
, from COMP to GND to cancel the
( )
C
R
LOAD
g
LOAD
2
mEA
G
MOD fC
G
R
MOD fC
C
MOD DC
C
V
, add a second compensa-
C
, the power-modulator gain
( )
V
FB
f
C
f
1
S
C
(
OUT
f
:
( )
S
(
f
zMOD
G
)
L
MOD fC
V
L
g
f
V
8
OUT
S
)
mc
FB
f
f
pMOD
zMOD
( )
C
OUT
R
R
LOAD
1
C
pMOD
f
pMOD
f
C
. C
15
C
C