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

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-.

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

PHONE

PART NUMBER

FAX

USA (814) 237-1431

LQH4N150K-TA

Murata-Erie

USA (814) 238-0490

USA (708) 956-0666

Japan (03) 3607-5111

CD43150

Sumida

USA (708) 956-0702

Japan (03) 3607-5428

USA (508) 853-5000

TMPD6050LT

Allegro

USA (508) 853-7556

USA (708) 803-6100

Japan (03) 3278-5111

NLC453232T-150K

TDK

USA (708) 803-6296

Japan (03) 3278-5358

USA (516) 435-1110

CMPSH-3 (Schottky)

Central Semiconductor

USA (516) 435-1824

USA (408) 749-0510

MMBD6050LT1 (silicon)

Motorola

USA (408) 991-7420

USA (401) 762-3800

PMBD6050 (silicon)

Philips

USA (401) 767-4493

USA (408) 749-0510

1N6050 (silicon),

1N5817 (Schottky)

Motorola

USA (408) 991-7420

Table 1. Suggested Component Suppliers

GND

T2

T1

T2OUT

R1IN

R2IN

T1OUT

C1-

C1+

V-

T2IN

R1OUT

R2OUT

T1IN

14

18

C3

1

µF

C1

0.47

µF

C4

1

µF

C2

1

µF

16

15

13

12

11

5, 17, 20

3

61

19

4

2

7

8

9

10

1.8V to

4.25V

LX

15

µH

1N6050

V+

FORCEON

INVALID

FORCEOFF

5k

5k

R1

R2

MAX3218

Figure 1. Typical Operating Circuit

Inductors

Diodes—Surface-Mount

Diodes—Through-Hole