MAX1514 Maxim Integrated Products, MAX1514 Datasheet - Page 20

• Manufacturer Part Number: MAX1514
• Description: (MAX1513 / MAX1514) TFT-LCD Power-Supply Controllers
• Manufacturer: Maxim Integrated Products

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Because V
cuit in Figure 9 should be used and the scale factor is:
Calculate R
The closest 1% standard values for R
866Ω and 1.13kΩ, respectively.
If the 2.2µH inductor used in the typical operating cir-
cuit (Figures 1 and 2) has a typical DCR of 10mΩ and a
maximum DCR of 14mΩ, the RC time constant of the
sense network is:
TFT-LCD Power-Supply Controllers
20
Figure 10. Lossless Current Sensing with V
V
SENSE
V
IN
______________________________________________________________________________________
C
=
S+
SENSE
S1
2 6
R
R
.
S
S
1
and R
2
A
SF
C
S
=
MAX1513
MAX1514
=
τ
×
would be greater than 100mV, the cir-
=
489
0 571
=
L
56
856
S2
.
1
100
175
m
2 2
10
R
:
Ω
S4
-
.
Ω
×
m
0 571
µ
mV
mV
(
=
.
Ω
1
H
0 571
C
GATE
.
+
S-
GND
856
FB
=
=
R
0 005
S3
.
220
Ω
0 571
=
.
µ
1139
s
×
SENSE
S1
40
Ω
°
and R
C
< 80mV
)
=
175
S2
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V
MAIN
are
mV
Select C
Assuming ∆T is 40°C and TC is 0.5%, the worst-case
high sense voltage over temperature is:
Because V
circuit in Figure 10 can be used to improve the current-
limit accuracy. Calculate R
The closest 1% standard values for R
2.61kΩ and 14.0Ω, respectively.
The output capacitor and its equivalent series resistance
(ESR) affect the circuit’s stability, output voltage ripple,
and transient response. The Output-Capacitor Stability
Requirement section discusses the output capacitance
requirement based on the loop stability. This section
deals with how to determine the output capacitance
according to the ripple voltage and load-transient
requirements.
The total output voltage ripple has two components: the
ohmic ripple due to the capacitor’s equivalent series
resistance (ESR), and the capacitive ripple caused by
the charging and discharging of the output capacitance:
where V
lator, I
capacitance, R
f
inductor current (see the Inductor Selection section).
R
R
OSC
S
S
V
3
4
SENSE
is the switching frequency, and I
=
=
MAIN
1
V
V
V
MAIN
S
2614
5V -
RIPPLE
RIPPLE ESR
RIPPLE C
= 0.1µF, R
=
SENSE
2 6
is the output current, C
Ω
.
4
is the output voltage of the step-up regu-
.5V -
ESR
(
( )
A
-
R
15
S
2600
=
would be much less than 80mV, the
×
V
≈
)
V
=
is the ESR of the output capacitor,
14
S
-
RIPPLE ESR
0
Ω
C
I
≈
MAIN
is:
.1V
m
4 5
220
0 1
OUT
.
.
Ω
=
I
PEAK
V
µ
µ
S3
+
14
Output-Capacitor Selection
(
F
(
1 0 005 40
s
0 044
×
Ω
+
and R
.
=
×
⎛
⎜
⎝
)
.
V
2200
+
R
V
MAIN
V
MAIN
ESR
S4
V
×
×
RIPPLE C
OUT
:
Ω
PEAK
2600
S3
×
-
°
C
f
is the output
and R
V
OSC
Ω
( )
IN
)
is the peak
=
=
⎞
⎟
⎠
44
2614
S4
mV
are
Ω
DataShee