DA9021 datasheet(140/142 Pages) DIALOG

140 / 142 page

DA9021/22

System PMIC with high efficiency USB power manager

Company confidential

Datasheet

Revision 2.5

17-Feb-2017

CFR0011-120-00 Rev 5

140 of 142

25.2.2

Power supply rejection

Power supply rejection (PSRR) is especially important in the supplies to the RF and audio parts of

the telephone. In a TDMA system such as GSM, the 217 Hz transmit burst from the power amplifier

results in significant current pulses being drawn from the battery. These can peak at up to 2 A before

reaching a steady state of 1.4 A (see below). Due to the battery having a finite internal resistance

(typically 0.5

Ω) these current peaks induce ripple on the battery voltage of up to 500 mV. As the

supplies to the audio and RF are derived from this supply it is essential that this ripple is removed

otherwise it would show as a 217 Hz tone in the audio and could also affect the transmit signal.

Power supply rejection should always be specified under worst case conditions when the battery is at

its minimum operating voltage, when there is minimum headroom available due to dropout.

25.2.3

Line regulation

Static line regulation is a measurement that indicates a change in the regulator output voltage

∆Vreg

(regulator operating with a constant load current) in response to a change in the input voltage

∆Vin.

Transient line regulation is a measurement of the peak change

∆Vreg in regulated voltage seen

when the line input voltage changes.

4.6ms TDMA frame rate

577µS

bat

reg

Figure 49: Line regulation

25.2.4

Load regulation

Static load regulation is a measurement that indicates a change in the regulator output voltage ∆Vreg

in response to a change in the regulator loading ∆load whilst the regulator input voltage remains

constant. Transient load regulation is a measurement of the peak change in regulated voltage ∆Vreg

seen when the regulator load changes.

reg

load max

load min

Figure 50: Load regulation

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