|TEA1093 Datasheet PDF : 28 Pages |
Supply: pins SUP, SREF, VBB, GND, VA and PD
As can be seen from Fig.4, the line current is divided
between the speech-transmission circuit (ITR + ICC) and
the TEA1093 circuit (ISUP). It can be shown that:
ISUP = Iline − ITR − ICC
ITR = VSUP − VSREF/RSREF
VSUP − VSREF = 315 mV
RSREF = 100 Ω
ICC ≈ 1 mA
It follows that ISUP ≈ ILINE − 4 mA.
The TEA1093 stabilizes its own supply voltage of 3.6 V at
VBB. The voltage on VBB can be adjusted by means of an
external resistor RVA.
When RVA is connected between pin VA and GND, the
voltage on VBB is increased, when connected between
pin VA and VBB, it is decreased. This is shown in Fig.5.
Two capacitors of 4.7 nF (CSREF and CSTAB) are required
to ensure stability of the supply block. When VSUP is
greater than VBB + 0.4 V, the current ISUP is supplied to
VBB via TR1. When VSUP is less, the current is shunted to
GND via TR2, which prevents distortion on the line.
To reduce current consumption during pulse dialling or
register recall (flash), the TEA1093 is provided with a
power-down (PD) input. When the voltage on PD is HIGH,
the current consumption from SUP is 55 µA and from
VBB 400 µA. Therefore a capacitor of 470 µF (CVBB) is
sufficient to power the TEA1093 during pulse dialling.
handbook, full pagewidth
7 SREF V V
limiter POWER PD 17
VA 15 RVA
Fig.4 Supply arrangement.
1996 Feb 09
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