UT3223G-R20-R datasheet(6/9 Pages) UTC

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UT3223

Preliminary

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

6 of 9

www.unisonic.com.tw

QW-R502-A91.e

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DETAILED DESCRIPTION

Charge-Pump Voltage Converter

The UTC UT3223 consists of a regulated dual charge pumps that provide output voltages of +5.5V and -5.5V,

regardless of the input voltage (VCC) changing from +3.0V to +5.5V.

The charge pumps operate in a discontinuous mode: if the output voltages are less than 5.5V, the charge pumps

are enabled; if the output voltages exceed 5.5V, the charge pumps are disabled.

Each charge pump requires a flying capacitor (C1, C2) and a reservoir capacitor (C3, C4) to generate the V+ and

V- supplies, refer to application circuit.

RS-232 Transmitters

UTC UT3223’s transmitters are inverting level translators that convert CMOS-logic levels to 5.0V EIA/TIA-232

levels. They guarantee a 250kbps data rate with worst-case loads of 3kΩ in parallel with 1000pF, providing

compatibility with PC-to-PC communication software.

Transmitters can be paralleled to drive multiple receivers or mouse. When FORCEOFF is driven to ground, or

shutdown circuitry senses invalid voltage levels at all receiver inputs, the transmitters are disabled and the outputs

are forced into a high-impedance state.

RS-232 Receivers

The UTC UT3223’s receivers convert RS-232 signals to CMOS-logic output levels. All receivers have one

inverting three-state output. In shutdown or in autoshutdown, the UT3223’s receivers are active. Drive EN high to

place the receiver in a high-impedance state.

Table 1. EN Control Truth Table

R_OUT

Active

High-Z

Shutdown Function

A 1µA supply current is achieved with shutdown feature, which operates when FORCEON is low and

FORCEOFF is high. When the UTC UT3223 senses no valid signal levels on all receiver inputs for 30µs, the

on-board power supply and drivers are shut off, reducing supply current to 1µA. This occurs if the RS-232 cable is

disconnected or the connected peripheral transmitters are turned off. The system turns on again when a valid level is

applied to any RS-232 receiver input. As a result, the system saves power without changes to the existing BIOS or

operating system. INVALID indicates the receiver inputs’ condition, when using shutdown function, the INVALID

output is high when the device is on and low when the device is shut down.

Table 2. Shutdown Logic Control Truth Table

OPERATION STATUS

FORCEOFF

INPUT

FORCEON

INPUT

INVALID

OUTPUT

T_OUT

Normal Operation (Forced On)

Active

Normal Operation (AutoShutdown)

Active

Normal Operation (AutoShutdown)

High-Z

Shutdown (Forced Off)

High-Z

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