MAX17007EVKIT+ Maxim Integrated Products, MAX17007EVKIT+ Datasheet - Page 29

• Manufacturer Part Number: MAX17007EVKIT+
• Description: KIT EVAL FOR MAX17007
• Manufacturer: Maxim Integrated Products
• Series: Quick-PWM™r

Specifications of MAX17007EVKIT+

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 2, Non-Isolated
• Voltage - Output: 1.2V, 1.5V
• Current - Output: 12A, 12A
• Voltage - Input: 7 ~ 24V
• Regulator Topology: Buck
• Frequency - Switching: 270kHz, 330kHz
• Board Type: Fully Populated
• Utilized Ic / Part: MAX17007
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

The minimum current-limit threshold must be high
enough to support the maximum load current when the
current limit is at the minimum tolerance value. The val-
ley of the inductor current occurs at I
half the ripple current; therefore:
where I
threshold voltage divided by the output sense element
(inductor DCR or sense resistor).
The four-level ILIM setting sets a valley current limit of
15mV, 30mV, 45mV, or 60mV across the CSH_ to CSL_
differential input.
Special attention must be made to the tolerance and
thermal variation of the on-resistance in the case of
DCR sensing. Use the worst-case maximum value for
R
gin for the rise in R
eral rule is to allow 0.5% additional resistance for each
°C of temperature rise, which must be included in the
design margin unless the design includes an NTC ther-
mistor in the DCR network to thermally compensate the
current-limit threshold.
The current-sense method (Figure 14) and magnitude
determine the achievable current-limit accuracy and
power loss. The sense resistor can be determined by:
Figure 14. Current-Sense Configurations (Sheet 1 of 2)
DCR
from the inductor data sheet, and add some mar-
LIMIT(LOW)
I
LIMIT LOW
a) OUTPUT SERIES RESISTOR SENSING
Setting the Valley Current Limit
Core Controllers for Notebook Computers
R
(
MAX17007
MAX17008
SENSE_
______________________________________________________________________________________
DCR
equals the minimum current-limit
)
>
I
PGND
Dual and Combinable QPWM Graphics
CSH_
with temperature. A good gen-
CSL_
LOAD MAX
= V
DH_
DL_
LX_
N
LIM_
PH
(
/I
N
N
LIMIT_
H
)
L
⎛
⎜
⎝
1
LOAD(MAX)
−
LIR
2
⎞
⎟
⎠
C
D
IN
L
INPUT (V
minus
L
IN
)
For the best current-sense accuracy and overcurrent
protection, use a 1% tolerance current-sense resistor
between the inductor and output as shown in Figure
14a. This configuration constantly monitors the inductor
current, allowing accurate current-limit protection.
However, the parasitic inductance of the current-sense
resistor can cause current-limit inaccuracies, especially
when using low-value inductors and current-sense
resistors. This parasitic inductance (L
celled by adding an RC circuit across the sense resis-
tor with an equivalent time constant:
Alternatively, low-cost applications that do not require
highly accurate current-limit protection can reduce the
overall power dissipation by connecting a series RC
circuit across the inductor (Figure 14b) with an equiva-
lent time constant:
and:
where R
R
worst-case inductance and R
the inductor manufacturer, adding some margin for the
inductance drop over temperature and load.
DCR
R
L
SENSE RESISTOR
EQ
ESL
is the inductor’s series DC resistance. Use the
CS
is the required current-sense resistance and
C
R
EQ
SENSE
R
DCR
C
R
EQ EQ
CS
=
R
=
C
R
L
EQ
1
R
=
+
C
2
R
R
×
OUT
2
L
SENSE
⎡
⎢
⎣
DCR
ESL
R
R
1
1
C
DCR
EQ
+
R
values provided by
EQ
R
1
2
=
ESL
⎤
⎥
⎦
R
L
SENSE
ESL
) can be can-
29