TC820CKW データシートの表示（PDF） - TelCom Semiconductor Inc => Microchip

部品番号

コンポーネント説明

メーカー

TC820CKW

3-3/4 DIGIT A/D CONVERTER WITH FREQUENCY COUNTER AND LOGIC PROBE

TelCom Semiconductor Inc => Microchip 

3-3/4 A/D CONVERTER WITH

FREQUENCY COUNTER

1

AND LOGIC PROBE

TC820

HIGH *

LOW **

* "HIGH" ANNUNCIATOR WILL BE ON WHEN DP1/HI =

LOGIC HIGH

** "LOW" ANNUNCIATOR AND BUZZER WILL BE ON

WHEN DP0/LO = LOGIC HIGH

Figure 7. LCD During Logic Probe Operation

To prevent roll-over-type errors from being induced by

large common-mode voltages, CREF should be large com-

pared to stray node capacitance. A 0.1µF capacitor is

typical.

The TC820 offers a significantly improved analog

common temperature coefficient, providing a very stable

voltage suitable for use as a voltage reference. The

temperature coefficient of analog common is typically

35ppm/°C.

Analog Common

2 The analog common pin is set at a voltage potential

approximately 3.3V below VDD. This potential is guaranteed

to be between 3.15V and 3.45V below VDD. Analog common

is tied internally to an N-channel FET capable of sinking

3mA. This FET will hold the common line at 3.3V below VDD

should an external load attempt to pull the common line

toward VDD. Analog common source current is limited to

12µA, and is therefore easily pulled to a more negative

3 voltage (i.e., below VDD – 3.3V).

The TC820 connects the internal VI+N and VI–N inputs to

analog common during the auto-zero cycle. During the

reference integrate phase, VI–N is connected to analog

common. If VI–N is not externally connected to analog common,

a common-mode voltage exists. This is rejected by the

converter's 86dB common-mode rejection ratio. In battery-

powered applications, analog common and VI–N are usually

4 connected, removing common-mode voltage concerns. In

systems where VI–N is connected to the power supply ground

or to a given voltage, analog common should be connected

to VI–N.

The analog common pin serves to set the analog section

reference or common point. The TC820 is specifically

designed to operate from a battery or in any measurement

SEGMENT

DRIVE

LCD

5

BP1

BP3

MEASURED

VBUF CAZ VINT

BP2

SYSTEM

VI+N

V+

V–

GND

VI–N

TC820

ANALOG

COMMON

VR–EF

VR+EF

VDD

OSC1

VSS

OSC2

OSC3 NC

6

V+ V –

POWER GND

SOURCE

+

9V

Figure 8. Common-Mode Voltage Removed in Battery Operation With VI–N = Analog Common

7

TELCOM SEMICONDUCTOR, INC.

8

3-161

Share Link: