UT3227G-R16-R datasheet(6/9 Pages) UTC

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UT3227

Preliminary

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

6 of 9

www.unisonic.com.tw

QW-R103-146.a

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DETAILED DESCRIPTION

Charge-Pump Voltage Converter

The UTC UT3227 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 Transmitter

UTC UT3227’s transmitter is inverting level translators that convert CMOS-logic levels to 5.0V EIA/TIA-232 levels.

They guarantee a 1Mbps data rate with worst-case loads of 3kΩ in parallel with 1000pF, providing compatibility with

PC-to-PC communication software.

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

shutdown circuitry senses invalid voltage levels at receiver input, the transmitter is disabled and the output are

forced into a high-impedance state.

RS-232 Receiver

The UTC UT3227’s receiver convert RS-232 signals to CMOS-logic output levels. The receiver has one inverting

three-state output. In shutdown or in autoshutdown, the UT3227’s receiver is active.

The UTC UT3227 features an INVALID output that is enabled low when no valid RS-232 voltage levels have been

detected on receiver input. Because INVALID indicates the receiver input’s condition, it is independent of FORCEON

and FORCEOFF states

Table 1. INVALID Control Truth Table

RS-232 SIGNAL PRESENT AT RECEIVER INPUT

INVALID

OUTPUT

YES

High

Low

Shutdown Function

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

FORCEOFF is high. When the UTC UT3227 do not sense a valid signal transition on any receiver and transmitter

input for 30sec, the on-board charge pumps are shutdown, 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 transition is applied to any RS-232 receiver or transmitter input (Table 2). 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

Valid signal at

Transmitter or

Receiver

T1OUT

Normal Operation (AutoShutdown

Disable)

Active

Normal Operation (AutoShutdown)

YES

Active

Normal Operation (AutoShutdown)

High-Z

Shutdown

High-Z

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