PCA5007 datasheet(59/112 Pages) PHILIPS

59 / 112 page

1998 Oct 07

Philips Semiconductors

Product speciﬁcation

Pager baseband controller

PCA5007

6.22.2

TYPICAL OPERATING CHARACTERISTICS

The maximum power delivered by the DC/DC converter is

given by equation (1).

(1)

Rs is the total series resistance which is the sum of

RBAT +Rind +Rsw + ESR(Co). In Figs 30 and 31 the

maximum available output current (IL) is shown as a

function of VBAT and Rs.

o(max)

Bat

()

--------------------

≤

The efficiency is determined by the series resistance RS

and the current consumption of the converter itself. RS is

the sum of the battery resistance RBAT, the DC resistance

SRL of the coil, the on resistance of the MOSFET RDS,on

and the ESR of the output capacitor Co. Figure 32a shows

the efficiency when using a 470

µH coil with a SRL of 5 Ω

and a load capacitor of 4.7

µF with an ESR of 0.5 Ω.

In Fig.32b the efficiency for the same configuration is

shown but with a SRL of only 0.1

Ω. To increase efficiency

for extremely low output currents, the converter should be

set into standby mode (see Fig.33).

Fig.30 Maximum available output current (mA) in normal mode.

VDD = 2.2 V; RS =RBAT +Rind +Rsw

handbook, full pagewidth

MGR345

0.8

1.2

1.6

1.4

VBAT (V)

(

Ω)

100

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