http://www.union-ic.com Rev.01 Mar.2015

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UM3243

Typical Operating Circuits

C1+

C1-

C2+

C2-

TIN1

TIN2

TIN3

ROUT2B

ROUT1

ROUT2

ROUT3

ROUT4

ROUT5

FORCEON

FORCEOFF

INVALID

GND

25

5k

Ω

RIN5

5k

Ω

5k

Ω

5k

Ω

5k

Ω

RIN4

RIN3

RIN2

RIN1

TOUT3

TOUT2

TOUT1

V-

V+

26

27

3

9

10

11

4

5

6

7

8

21

22

23

15

16

17

18

19

20

12

13

14

2

1

24

28

+3.3V

0.1µF

C1+

0.1µF

0.1µF

0.1µF

0.1µF

C2

LOGIC

INPUTS

LOGIC

OUTPUTS

TO POWER

MANAGEMENT UNIT

RS-232

INPUTS

RS-232

OUTPUTS

C4

C3

UM3243

+

+

+

+

Figure 7

Application Information

RS-232 Receivers

The UM3243’s receivers convert RS-232 signals to CMOS-logic output levels. All receivers have

inverting three-state outputs and can be active or inactive. The UM3243’s receivers are

high-impedance when the part is in Forced Power-Off mode (FORCEOFF

_____________________

=low).

The UM3243 features an always-active complementary output (ROUT2B). ROUT2B monitors

receiver activity while the other receivers are high-impedance. This allows Ring Indicator to be

monitored without forward biasing other devices connected to the receiver outputs. This is ideal for

The UM3243 features an INVALID

_________________

output that is enabled low when no valid RS-232 signal levels

have been detected on all receiver inputs. INVALID

_________________

is functional in any mode (Figure 6).