MT91600AN1 데이터 시트보기 (PDF) - Zarlink Semiconductor Inc

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MT91600AN1

Programmable SLIC

Zarlink Semiconductor Inc 

MT91600

From (Equation 1)

R11 = k * (R1 + R2)

R11 = 120 * (220Ω + 220Ω)

∴ R11 = 52k8Ω

Power Sharing Resistor (R23)

To determine the value of R23, use the following equations:

R23(max)= |Vbat(min)| - 100 - (2*R2 + Lr + DCRP)

30mA

R23(min)= |Vbat(max)| - Pd(max) - R2

40mA 1.6mA

where,

Vbat(min/max) = the expected variation of Vbat.

R2 = the feed resistor.

Lr = maximum DC loop resistance.

DCRP = DC resistance of the phone set.

Pd(max) = the maximum power dissipation of the ring drive transistor Q3.

If R23(max) > R23(min), then set R23 to be the geometric center:

R23 = Square Root (R23(max) * R23(min))

If R23(max) < R23(min), then a violation has occurred. Pd(max) will have to be increased.

If R23 = negative value, power sharing is not required, i.e., R23=0

A numerical example:

Given:

R2 = 220Ω

Lr = 325Ω (2.5km of 28 gauge wire, averaged at 65Ω/km)

DCRP = 200Ω

Pd(max) = 1.5W

Vbat = -48V +/- 10% (i.e. -43V to -53V)

Therefore:

R23(max) = (43/30mA) - 100 - (2 * 220 + 325 + 200)

= 1433.3 - 100 - 965

R23(max) = 368.3Ω

R23(min) = (53/40mA) - (1.5/1.6mA) - 220

= 1325 - 937.5 - 220

R23(min) = 167.5 Ω

R23 = Square Root ( 368.3 * 167.5 )

R23 = 248.4Ω

Data Sheet

9

Zarlink Semiconductor Inc.

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