MAX8760ETL+T Maxim Integrated Products, MAX8760ETL+T Datasheet - Page 36

• Manufacturer Part Number: MAX8760ETL+T
• Description: IC CNTRLR QUICK PWM 40-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX8760ETL+T

• Applications: Controller, 6-bit VID AMD Mobile Turion™
• Voltage - Input: 4 ~ 28 V
• Number Of Outputs: 2
• Voltage - Output: 0.38 ~ 1.55 V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 40-TQFN Exposed Pad
• Output Voltage: 0.375 V to 1.55 V
• Output Current: 4000 mA
• Mounting Style: SMD/SMT
• Switching Frequency: 550 KHz
• Maximum Operating Temperature: + 100 C
• Minimum Operating Temperature: - 40 C
• Synchronous Pin: No
• Topology: Buck
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

increased load, and must always be greater than 1. As
h approaches 1, the absolute minimum dropout point,
the inductor current cannot increase as much during
each switching cycle and V
unless additional output capacitance is used.
A reasonable minimum value for h is 1.5, but adjusting
this up or down allows tradeoffs between V
capacitance, and minimum operating voltage. For a
given value of h, the minimum operating voltage can be
calculated as:
where η
ing regulators, V
V
the discharge and charge paths (see the On-Time One-
Shot (TON) section), t
Characteristics table, and K is taken from Table 6. The
absolute minimum input voltage is calculated with h = 1.
If the calculated V
imum input voltage, then reduce the operating frequency
or add output capacitance to obtain an acceptable V
If operation near dropout is anticipated, calculate V
be sure of adequate transient response.
Dual-Phase, Quick-PWM Controller for AMD
Mobile Turion 64 CPU Core Power Supplies
Figure 10. Voltage-Positioning Gain
36
DROP1
V
IN MIN
______________________________________________________________________________________
(
OUTPH
and V
)
=
+
η
V
OUTPH
DROP2
is the total number of out-of-phase switch-
DROP
VPS
IN(MIN)
COMPARATOR
2
⎡
⎢
⎢
⎢
⎢
⎣
is the voltage-positioning droop,
are the parasitic voltage drops in
-
1
ERROR
OFF(MIN)
V
-
is greater than the required min-
DROP
V
η
FB
OUTPH
MAX8760
-
1
SAG
V
+
is from the Electrical
VPS
V
⎛
⎜
⎝
VPS
h x t
greatly increases
+
V
OFF MIN
DROP
OAIN+
OAIN-
K
CMN
CMP
CSN
CSP
FB
SAG
(
1
SECOND
, output
PHASE
PHASE
)
SAG
MAIN
⎞
⎟
⎠
⎤
⎥
⎥
⎥
⎥
⎦
SAG
R
F
to
.
Dropout design example:
V
K
t
V
V
h = 1.5 and η
Calculating again with h = 1 gives the absolute limit of
dropout:
Therefore, V
large output capacitance, and a practical input voltage
with reasonable output capacitance would be 5V.
L1
L2
OFF(MIN)
FB
VPS
DROP1
MIN
= 1.4V
V
V
= 3mV/A × 30A = 90mV
= 3µs for f
IN MIN
IN MIN
(
(
R
R
= V
R
R
A
A
SENSE
SENSE
= 400ns
DROP2
)
IN
)
R
R
B
B
OUTPH
=
=
must be greater than 4.1V, even with very
2
2
SW
+
+
x
150
x
150
= 150mV (30A load)
= 300kHz
R
⎡
⎢
⎣
⎡
⎢
⎣
FBS
= 2
1 2
1 2
mV
mV
-
1 4
-
1 4
.
.
V
-
V
-
x
x
PC BOARD TRACE
RESISTANCE
CPU SENSE
POINT
PC BOARD TRACE
RESISTANCE
150
150
-
( .
-
( .
0 4
0 4
90
90
mV
mV
mV
µ
mV
µ
s x
s x
+
+
+
+
1 5 3 0
90
1 0 3 0
90
150
. / .
150
. / .
mV
mV
mV
mV
=
=
µ
µ
s
4 96
s
4 07
.
⎤
⎥
⎦
.
⎤
⎥
⎦
V
V