MAX8524 MAXIM [Maxim Integrated Products], MAX8524 Datasheet - Page 16

• Manufacturer Part Number: MAX8524
• Description: 2- to 8-Phase VRM 10/9.1 PWM Controllers with Precise Current Sharing and Fast Voltage Positioning
• Manufacturer: MAXIM [Maxim Integrated Products]

See the Clock Frequency vs. R
Operating Characteristics section for the relationship
between the clock frequency and the value of the fre-
quency-setting resistor, R
given clock frequency can also be approximated from
equation 3:
Output inductance is set by the desired amount of
inductor current ripple (LIR) and the slew rate of the
inductor current during a load transient. A larger induc-
tance value minimizes output ripple current and increas-
es efficiency but slows down the current slew rate. For
the best tradeoff of size, cost, and efficiency, an LIR of
30% to 60% is recommended (LIR = 0.3 to 0.6). Choose
LIR close to the high end when more phases are used.
The inductor value is determined from:
2- to 8-Phase VRM 10/9.1 PWM Controllers
with Precise Current Sharing and Fast Voltage
Positioning
Figure 6. Master and Slave Controller Connections
16
______________________________________________________________________________________
R
OSC
L
=
≥
VID0 INPUT
VID1 INPUT
VID2 INPUT
VID3 INPUT
VID4 INPUT
VID5 INPUT
277 704
REMOTE-SENSE
LIR
INPUT
V
INPUT
.
OUT
EN
×
f
Output Inductor Selection
SW
×
×
f
(
OSC
OSC MHz
1
×
−
I
OUT MAX
. The value of R
(
D
OSC
)
×
_
VID0
VID1
VID2
VID3
VID4
VID5
RS+
RS-
)
1 - .197
graph in the Typical
N
EN
MAX8524/
MAX8525
H
MASTER
k
Ω
(
Eq
OSC
COMP
CLKO
(
Eq
REF
4
)
for a
3
)
where f
maximum-rated output current, D is the duty ratio, and
V
the output-inductance ripple current for the ripple volt-
age it produces across the output capacitor ESR. For
an n-phase VRM converter, the output ripple voltage,
V
For ripple voltage estimate, it is safe to replace
R
output ripple voltage is not satisfied, a larger value of
output inductance should be chosen. The selected
inductor should have the lowest possible DC resistance
and the saturation current should be greater than the
peak inductor current, I
When the DC resistance of the output inductor is used
for current sensing, the range of DC resistances is limit-
ed by the following constraints:
V
OUT
RIPPLE
ESR_CO
RIPPLE
is the output voltage at a given VID code. Check
SW
I
, can be calculated using:
PEAK
=
with R
V
is the switching frequency, I
OUT
=
I
O
OUT MAX
×
, the VRM output impedance. If the
R
VID0
VID1
VID2
VID3
VID4
VID5
CLKI
REF
COMP
_
ESR CO
EN
PEAK
f
SW
MAX8524/
_
MAX8525
(
SLAVE
2
. I
2
×
+
PEAK
×
×
L
LIR
(
N
1
RS+
RS-
−
)
is found from:
(
N
OUT_MAX
×
(
Eq
D
)
6
)
)
(
Eq
is the
5
)