Datasheet

MAX3218
Diode Selection
Key diode specifications are fast recovery time (<10ns),
average current rating (>100mA), and peak current rat-
ing (>350mA). Inexpensive fast silicon diodes, such as
the 1N6050, are generally recommended. More expen-
sive Schottky diodes improve efficiency and give slightly
better performance at very low V
CC
voltages. Table 1
lists suppliers of both surface-mount and through-hole
diodes. 1N914s are usually satisfactory, but specifica -
tions and performance vary widely with different manu-
facturers.
Capacitor Selection
Use capacitors with values at least as indicated in
Figure 1. Capacitor C2 determines the ripple on V+, but
not the absolute voltage. Capacitors C1 and C3 deter -
mine both the ripple and the absolute voltage of V-.
Bypass V
CC
to GND with at least 1 µF (C4) placed close
to pins 5 and 6. If the V
CC
line is not bypassed else -
where (e.g., at the power supply), increase C4 to 4.7µF.
You may use ceramic or polarized capacitors in all
locations. If you use polarized capacitors, tantalum
types are preferred because of the high operating fre-
quency of the power supplies (about 250kHz). If alu-
minum electrolytics are used, higher capacitance
values may be required.
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
6 _______________________________________________________________________________________
MANUFACTURER PHONEPART NUMBER FAX
USA [phone]LQH4N150K-TAMurata-Erie USA [phone]
USA [phone]
Japan [phone]
CD43150Sumida
USA [phone]
Japan [phone]
USA [phone]TMPD6050LTAllegro USA [phone]
USA [phone]
Japan [phone]
NLC453232T-150KTDK
USA [phone]
Japan [phone]
USA [phone]CMPSH-3 (Schottky)Central Semiconductor USA [phone]
USA [phone]MMBD6050LT1 (silicon)Motorola USA [phone]
USA [phone]PMBD6050 (silicon)Philips USA [phone]
USA (408) 749-05101N6050 (silicon),
1N5817 (Schottky)
Motorola
USA [phone]
Table 1. Suggested Component Suppliers
GND
T2
T1
T2OUT
R1IN
R2IN
T1OUT
C1-
C1+
V-
T2IN
R1OUT
R2OUT
T1IN 14
18
C3
1µF
C1
0.47µF
C4
1µF
C2
1µF
16
15
13
12
11
5, 17, 20
V
CC
3
61
19
4
2
7
8
9
10
1.8V to
4.25V
LX
15µH 1N6050
V+
FORCEON
INVALID
FORCEOFF
5k
5k
R1
R2
MAX3218


Figure 1. Typical Operating Circuit
Inductors
Diodes—Surface-Mount
Diodes—Through-Hole