MAX17480 Maxim Integrated Products, MAX17480 Datasheet - Page 32

• Manufacturer Part Number: MAX17480
• Description: AMD 2-/3-Output Mobile Serial VID Controller
• Manufacturer: Maxim Integrated Products

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AMD 2-/3-Output Mobile Serial
VID Controller
where L
current-sense resistor, R
tance value, and C
stant matching components.
Using the DC resistance (R
allows higher efficiency. In this configuration, the initial
tolerance and temperature coefficient of the inductor’s
DCR must be accounted for in the output-voltage
droop-error budget and power monitor. This current-
sense method uses an RC filtering network to extract
the current information from the output inductor (see
Figure 7). The time constant of the RC network should
match the inductor’s time constant (L/R
where C
components. To minimize the current-sense error due to
Figure 7. Current-Sense Configurations
32
______________________________________________________________________________________
ESL
SENSE
is the equivalent series inductance of the
and R
R
A) OUTPUT SERIES RESISTOR SENSING
B) LOSSLESS INDUCTOR DCR SENSING
R
L
SENSE
DCR
ESL
SENSE
L
EQ
MAX17480
MAX17480
=
are the time-constant matching
=
SENSE
R
R
EQ SENSE
and R
DCR
EQ SENSE
CSP_
CSN_
CSP_
CSN_
C
DH_
DH_
DL_
DL_
LX_
LX_
C
) of the output inductor
is current-sense resis-
EQ
are the time-con-
DCR
N
N
N
N
H
L
H
L
):
D
D
C
C
L
L
IN
IN
L
INPUT (V
INPUT (V
R
LX
IN
IN
C
)
)
LX
R1
R
SENSE RESISTOR
L
EQ
ESL
L
INDUCTOR
the current-sense inputs’ bias current (I
choose R
to determine the sense capacitance (C
capacitors with 5% tolerance and resistors with 1% tol-
erance specifications. Temperature compensation is
recommended for this current-sense method. See the
Core Voltage Positioning and Loop Compensation sec-
tion for detailed information.
Additional R
LX_ and CSP_ pins if DCR sensing is used, and they
provide additional overdrive to the current-sense signal
to improve the noise immunity; otherwise, there might
be too much jitter or the system could be unstable.
The NB current sense is achieved by sensing the volt-
age across the high-side internal MOSFET during the
on-time. The current information is computed by dividing
the sensed voltage by the MOSFET’s on-resistance,
R
ON(NH3)
R
R
SENSE
DCR
C
R2
EQ
C
EQ
EQ
.
LX
less than 2kΩ and use the above equation
FOR THERMAL COMPENSATION:
R2 SHOULD CONSIST OF AN NTC RESISTOR
IN SERIES WITH A STANDARD THIN-FILM
RESISTOR.
and C
C
C
OUT
OUT
LX
C
R
R
CS
DCR
EQ
are always added between the
R
=
EQ
=
R1 + R2
C
=
R2
L
EQ
R
L
SENSE
NB SMPS Current Sense
ESL
×
× R
R1
1
DCR
+
R2
1
SENSE
CSP
and I
). Choose
CSN
),