MAX8660ETL+T Maxim Integrated Products, MAX8660ETL+T Datasheet - Page 39

• Manufacturer Part Number: MAX8660ETL+T
• Description: IC POWER MANAGE XSCALE 40-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX8660ETL+T

• Applications: Processor
• Voltage - Supply: 2.6 V ~ 6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 40-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

inductance values than L
higher output current, but typically require physically
larger inductor size. Refer to the MAX8660 EV kit data
sheet for specific inductor recommendations.
The input capacitor in a step-down DC-DC converter
reduces current peaks drawn from the battery or other
input power source and reduces switching noise in the
controller. The impedance of the input capacitor at the
switching frequency should be less than that of the
input source so that high-frequency switching currents
do not pass through the input source.
The input capacitor must meet the input-ripple-current
requirement imposed by the step-down converter.
Ceramic capacitors are preferred due to their resilience
to power-up surge currents. Choose the input capacitor
so that the temperature rise due to input ripple current
does not exceed approximately 10°C. For a step-down
DC-DC converter, the maximum input ripple current is
1/2 of the output. This maximum input ripple current
occurs when the step-down converter operates at 50%
duty factor (V
Refer to the MAX8660 EV kit data sheet for specific
input capacitor recommendations.
The step-down DC-DC converter output capacitor
keeps output ripple small and ensures control-loop sta-
bility. The output capacitor must also have low imped-
ance at the switching frequency. Ceramic, polymer,
and tantalum capacitors are suitable, with ceramic
exhibiting the lowest ESR and lowest high-frequency
impedance.
Figure 12. Step-Down Converter Maximum Output Current Example
TO FIND THE ABSOLUTE WORST CASE MAXIMUM OUTPU
V
OUT
I
OUTMAX
=
1 2
. V V L
Voltage Management for Mobile Applications
IN
High-Efficiency, Low-I
,
= 2 x V
=
______________________________________________________________________________________
1
=
I
+
L L IM
Output Capacitor Selection
1 2
(
.
R
Input Capacitor Selection
D
OUT
N
µ
−
H
=
+
V
IDEAL
R
±
OUT
V
).
2
V
L
30
OUT
IN
× ×
)
%,
2
(
f L
1
+
1
× ×
+
−
can be used to obtain
I
−
OUTTAR
AND R
f L
I
D
OUTTAR
D
)
-
=
L
1
(
R
( (
=
+ +
R
N
( .
50
N
0 08
−
+
1 85
m
R
.
R
P
Ω
Ω
L
)
)
A
+
=
−
0 05
1 2
.
4 2
2
.
.
×
Ω
V
V
( .
1 9 10
)
+
+
2
1 6 0 08Ω 0 0 05
1 6 0 08
×
.
.
×
Output ripple due to capacitance (neglecting ESR) is
approximately:
Additional ripple due to capacitor ESR is:
Refer to the MAX8660 EV kit data sheet for specific out-
put capacitor recommendations.
The maximum output current for each step-down con-
verter is listed in the Electrical Characteristics table.
This current is guaranteed by correlation to the p-chan-
nel current-limit threshold, p-channel on-resistance, n-
channel on-resistance, oscillator frequency, input
voltage range, and output voltage range. The maximum
output current in the Electrical Characteristics table is
for the components shown in Figure 3 over then entire
specified range of input and output voltage. For differ-
ent components or voltage ranges, the maximum out-
put current changes. Typically, inductors with a higher
inductance increase the maximum output current, but
they are physically larger and decrease the output volt-
age response time due to a load transient.
Calculate the maximum output current for a particular
application using following the two-step process (see
Figure 12). Use the maximum expected value for input
voltage (V
the p-channel current-limit (I
(f), and inductance (L) provides the absolute worst-
case maximum output current (i.e., the lowest value).
T T CURRENT FOR REG WITH V
( .
A
1 9 10
A
( .
( .
Q
6
1 1 2 1 0 34
Hz
×
.
, PMICs with Dynamic
V
) ( .
Ω
(
×
Step-Down Converter Output Current
6
+
−
−
Hz
V
1 2 10
IN
RIPPLE
0 12
1 0 34
) ( .
.
.
.
−
). Using the minimum expected values for
×
V
×
RIPPLE(ESR)
Ω
)
1 2 10
Ω
.
)
)
−
6
=
=
×
0 34
H
2π
.
×
−
3
6 6
0 7
x f
. )
H
I
L PEAK
OSC
(
= I
×
0 7
L(PEAK)
. )
LIM
x C
IN
)
=
), oscillator frequency
OUT
=
0 482
.
3 2
.
x ESR
V TO
A
4 2
.
V
,
39