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| LTC2801 Datasheet, PDF (11/16 Pages) Linear Technology – 1.8V to 5.5V RS-232 Single and Dual Transceivers | |||
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LTC2801/LTC2802/
LTC2803/LTC2804
APPLICATIONS INFORMATION
Table 3. Recommended Inductors
PART
NUMBER
ISAT MAX DCR
(mA) (Ω)
SIZE
(mm)
MANUFACTURER
LQH2MCN100K02L 225
1.2 2 Ã 1.6 Ã 0.95 Murata
www.murata.com
LBC2016T100K
245 0.85 2 Ã 1.6 Ã 1.6 Taiyo Yuden
www.t-yuden.com
FSLB2520-100K 220 1.1 2.5 Ã 2 Ã 1.6 Toko
www.tokoam.com
Capacitor Selection
The small size of ceramic capacitors makes them ideal for
the LTC2801 family. X5R and X7R (preferred) types are
recommended because their ESR is low and they retain their
capacitance over relatively wide voltage and temperature
ranges. Use a voltage rating of at least 10V.
Table 4. Recommended Ceramic Capacitor Manufacturers
MANUFACTURER
URL
Murata
www.murata.com
TDK
www.tdk.com
Taiyo Yuden
www.t-yuden.com
AVX
www.avxcorp.com
Kemet
www.kemet.com
ï¬owing through inductor L1 and capacitors C1, C2. The
peak inrush current must not exceed 2A. To avoid this
condition, add a 1Ω resistor as shown in Figure 8. This
precaution is not relevant for supply voltages below 4.5V
or rise times longer than 10μs.
Board Layout
The board layout should minimize the length and area of
the SW and CAP traces. Suggested compact layouts for
the LTC2801 family are shown in Figure 9 (a) and (b).
VL
GND
C5
TOP VIEW
= VIA
C1
GND
GND
C2
L1
GND
C3
VCC
GND
C4
Inrush Current and Supply Overshoot Precaution
In certain applications, such as battery-operated and
wall-adapter devices, fast supply slew rates are generated
when power is connected. If VCCâs voltage is greater than
4.5V and its rise time is faster than 10μs, the pins VDD
and SW can exceed their ABS MAX values during start-
up. When supply voltage is applied to VCC, the voltage
difference between VCC and VDD generates inrush current
4.5V TO 5.5V
L1
10μH
C1
220nF
R1
1Ω
INRUSH
CURRENT
SW
CAP
1/8W
VCC
C4
1μF
VDD
GND
C2
1μF
SCALE R1 WITH C1, C2, 1/C4
2801F08
Figure 8. Supply Overshoot Protection for Input
Supplies of 4.5V or Higher
VL
C5
GND
C1
GND
GND
C2
L1
VCC
GND
C4
GND
C3
TOP VIEW
= VIA
2801F09
Figure 9. Recommended Board Layouts for (a) Single and
(b) Dual Transceiver Parts
2801234fc
11
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