MAX17528GTJ+ Maxim Integrated Products, MAX17528GTJ+ Datasheet - Page 24

• Manufacturer Part Number: MAX17528GTJ+
• Description: IC PWM CTRLR STP-DWN 32TQFN-EP
• Manufacturer: Maxim Integrated Products
• Series: Quick-PWM™r

Specifications of MAX17528GTJ+

• Applications: Controller, Intel IMVP-6.5™ GMCH
• Voltage - Input: 4.5 ~ 5.5 V
• Number Of Outputs: 1
• Voltage - Output: 0.01 ~ 1.5 V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 32-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 4. Current-Sense Methods
The current-limit circuit employs a “valley” current-sens-
ing algorithm that uses a current-sense element (see
Figure 4) between the current-sense inputs (CSP to
CSN) to detect the inductor current. If the differential
current-sense voltage exceeds the current-limit thresh-
old, the PWM controller does not initiate a new cycle
until the inductor current drops below the valley current-
limit threshold. Since only the valley current level is
actively limited, the actual peak inductor current
exceeds the valley current-limit threshold by an amount
equal to the inductor ripple current. Therefore, the exact
current-limit characteristic and maximum load capability
are a function of the current-sense impedance, inductor
value, and battery voltage. When combined with the
undervoltage protection circuit, this current-limit method
is effective in almost every circumstance.
1-Phase Quick-PWM
Intel IMVP-6.5/GMCH Controllers
24
______________________________________________________________________________________
A) OUTPUT SERIES RESISTOR SENSING
B) LOSSLESS INDUCTOR SENSING
MAX17528
MAX17528
PGND
PGND
CSP
CSN
CSP
CSN
DH
DL
DH
DL
LX
LX
N
N
N
N
H
H
L
L
D
D
C
C
L
L
IN
IN
Current Limit
L
INPUT (V
INPUT (V
R1
R1
L
SENSE RESISTOR
ESL
L
IN
IN
INDUCTOR
)
)
The positive valley current-limit threshold voltage at
CSP to CSN equals precisely 1/10 of the differential
TIME to ILIM voltage over a 0.1V to 0.5V range (10mV
to 50mV current-sense range). Connect ILIM directly to
V
22.5mV nominal.
The negative current-limit threshold (forced-PWM mode
only) is nominally -125% of the corresponding valley
current-limit threshold. When the inductor current drops
below the negative current limit, the controller immedi-
ately activates an on-time pulse—DL turns off, and DH
turns on—allowing the inductor current to remain above
the negative current threshold.
Carefully observe the PCB layout guidelines to ensure
that noise and DC errors do not corrupt the current-sense
signals seen by the current-sense inputs (CSP, CSN).
CC
R
SENSE
DCR
to set the default current-limit threshold setting of
C
C
R2
EQ
EQ
FOR THERMAL COMPENSATION:
R2 SHOULD CONSIST OF AN NTC RESISTOR IN
SERIES WITH A STANDARD THIN-FILM RESISTOR.
C
C
OUT
OUT
R
R
CS
C
DCR
EQ
=
R1 =
(
=
R1 + R2
C
R2
L
EQ
L
R
SENSE
SENSE
[
)
R
R1
DCR
1
+
R2
1
]