UT213

Preliminary

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

6 of 8

www.unisonic.com.tw

QW-R103-144.a



DETAILED DESCRIPTION

Charge-Pump Voltage Converter

The UTC UT213 consists of a regulated dual charge pumps that provide output voltages of +5.5V and -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 UT213’s transmitters are inverting level translators that convert CMOS-logic levels to 5.0V EIA/TIA-232 levels.

They guarantee a 120kbps data rate with worst-case loads of 3kΩ in parallel with 1000pF, providing compatibility

with PC-to-PC communication software.

Input thresholds are both CMOS and TTL compatible. The inputs of unused drivers can be left unconnected since

unused drivers low. The input pullup resistors typically source 15μA; therefore, the driver inputs should be driven

high or open circuited to minimize power-supply current in shutdown mode.

RS-232 Receivers

The UTC UT213’s receivers convert RS-232 signals to CMOS logic output levels. Receiver outputs are inverting,

maintaining compatibility with driver outputs. The guaranteed receiver input thresholds of +0.8V and +2.4V are

significantly tighter than the Q3.0V threshold required by the EIA/TIA-232E specification. This allows receiver inputs

to respond to TTL/CMOS logic levels and improves noise margin for RS-232 levels.

Receiver inputs have approximately +0.5V hysteresis. This provides clean output transitions, even with slow rise

and fall time input signals with moderate amounts of noise and ringing. In shutdown, the UTC UT213’s receivers R4

and R5 have no hysteresis.

During normal operation, the UTC UT213’s receiver propagation delay is typically 1us. When entering shutdown

with receivers active, R4 and R5 are not valid until 80Fs after SHDN is driven low. In shutdown mode, propagation

delays increase to 4us for a high-to-low or a low-to-high transition.

Shutdown Function

ground, and the transmitter outputs are disabled. This reduces supply current typically to 15μA. The time required to

exit shutdown is 1ms, All receivers except R4 and R5 on the UTC UT213 are put into a high-impedance state in

shutdown mode. The UTC UT213’s R4 and R5 receivers still function in shutdown mode. These two receivers are

useful for monitoring external activity while maintaining minimal power consumption.

The enable control is used to put the receiver outputs into a high-impedance state, so that the receivers can be

connected directly to a three-state bus. It has no effect on the RS-232 drivers or on the charge pumps.

Table 1. Shutdown Logic Control Truth Table

SHDN

EN

OPERATION STATUS

TRANSMITTERS T1–T4

R1, R2, R3

R4, R5

0

0

Shutdown

High-Z

High-Z

High-Z

0

1

Shutdown

High-Z

High-Z

Active*

1

0

Normal operation

Active

High-Z

High-Z

1

1

Normal operation

Active

Active

Active

* Active with reduced performance.