IEEE Solid-State Circuits Magazine - Summer 2017 - 22

VOUTN

VDD

MP

Power
Down

Power up

t

VOUTN
φ

φb

φ1

φ1b
MN
Half
H-Bridge

Pumping Up Pumping Down

FIGURE 21: Class D power driver ramping.

PWM Output

VDD

t

-VDD
Power Up

Normal Operation

Power Down

FIGURE 22: The differential PWM pulses during power up and power down.

Feedforward
ADC Path

Loop
Filter
RIN

+
-
+
-

PWM
GEN

Predriver
RFDBK

Feedback
Filter Path

FIGURE 23: The enhanced class D architecture.

is the half H-bridge and its predriver.
The source impedance of the predriver
is realized with the NMOS transistor
operating in the linear region. The
gate voltage of the NMOS transistor is

22

SU M M E R 2 0 17

slowly ramped with switched capacitor charge pump circuit. During power
up, the gate voltage Voutn is slowly
ramped up, while during power down,
the gate voltage is slowly ramped down.

IEEE SOLID-STATE CIRCUITS MAGAZINE

During power up, the gate voltage of
the PMOS power switch Mp is slowly
ramped down. As a result, the Mp onresistance is slowly ramped down.
The gate voltage of the NMOS power
switch Mn is also slowly ramped down,
implying that the NMOS switch is firmly
turned on initially. As a result, the
speaker is firmed tied to ground at the
beginning of power up. The differential PWM pulse during power up and
power down are shown in Figure 22.
Unlike a conventional class D amplifier
where the PWM pulses abruptly start
with rail-to-rail amplitude, the PWM
pulses are slowly ramped up during
power up and slowly ramped down during power down. It is worth mentioning that the dc offset is reflected by the
width of the PWM pulses. So the effective dc offset is also slowly ramped.
Enhanced analog feedback class D
architecture [15], shown in Figure 23,
resolves all of the aforementioned
issues. It includes a feedforward analog-to-digital converter (ADC) path,
feedback filters, and edge rate control
in the driver stage. The feedforward
path is designed to process the signal, using the loop filter to integrate
only the difference between the input
and the feedback signals. The loop
filter, therefore, mainly responds to
errors injected into the loop. This
architecture significantly extends the
loop filter operation range to support
a much larger signal level and, thus,
large output power capability. To avoid
PSRR performance degradation due
to the feedforward architecture, the
loop filter, feedback, and feedforward
paths are powered from an internal
low drop out regulator. The feedforward path basically provides a period
modulated ramp signal for PWM generation. This is very different from
conventional PWM generation with a
period-fixed ramp signal.
The feedforward path, as shown in
Figure 24, consists of an ADC, digital
PWM, and analog ramp generators.
The accuracy requirements for the
ADC and analog ramp circuits are
relaxed because the feedback loop
also attenuates any errors introduced
in the feedforward path. The digital



Table of Contents for the Digital Edition of IEEE Solid-State Circuits Magazine - Summer 2017

IEEE Solid-State Circuits Magazine - Summer 2017 - Cover1
IEEE Solid-State Circuits Magazine - Summer 2017 - Cover2
IEEE Solid-State Circuits Magazine - Summer 2017 - 1
IEEE Solid-State Circuits Magazine - Summer 2017 - 2
IEEE Solid-State Circuits Magazine - Summer 2017 - 3
IEEE Solid-State Circuits Magazine - Summer 2017 - 4
IEEE Solid-State Circuits Magazine - Summer 2017 - 5
IEEE Solid-State Circuits Magazine - Summer 2017 - 6
IEEE Solid-State Circuits Magazine - Summer 2017 - 7
IEEE Solid-State Circuits Magazine - Summer 2017 - 8
IEEE Solid-State Circuits Magazine - Summer 2017 - 9
IEEE Solid-State Circuits Magazine - Summer 2017 - 10
IEEE Solid-State Circuits Magazine - Summer 2017 - 11
IEEE Solid-State Circuits Magazine - Summer 2017 - 12
IEEE Solid-State Circuits Magazine - Summer 2017 - 13
IEEE Solid-State Circuits Magazine - Summer 2017 - 14
IEEE Solid-State Circuits Magazine - Summer 2017 - 15
IEEE Solid-State Circuits Magazine - Summer 2017 - 16
IEEE Solid-State Circuits Magazine - Summer 2017 - 17
IEEE Solid-State Circuits Magazine - Summer 2017 - 18
IEEE Solid-State Circuits Magazine - Summer 2017 - 19
IEEE Solid-State Circuits Magazine - Summer 2017 - 20
IEEE Solid-State Circuits Magazine - Summer 2017 - 21
IEEE Solid-State Circuits Magazine - Summer 2017 - 22
IEEE Solid-State Circuits Magazine - Summer 2017 - 23
IEEE Solid-State Circuits Magazine - Summer 2017 - 24
IEEE Solid-State Circuits Magazine - Summer 2017 - 25
IEEE Solid-State Circuits Magazine - Summer 2017 - 26
IEEE Solid-State Circuits Magazine - Summer 2017 - 27
IEEE Solid-State Circuits Magazine - Summer 2017 - 28
IEEE Solid-State Circuits Magazine - Summer 2017 - 29
IEEE Solid-State Circuits Magazine - Summer 2017 - 30
IEEE Solid-State Circuits Magazine - Summer 2017 - 31
IEEE Solid-State Circuits Magazine - Summer 2017 - 32
IEEE Solid-State Circuits Magazine - Summer 2017 - 33
IEEE Solid-State Circuits Magazine - Summer 2017 - 34
IEEE Solid-State Circuits Magazine - Summer 2017 - 35
IEEE Solid-State Circuits Magazine - Summer 2017 - 36
IEEE Solid-State Circuits Magazine - Summer 2017 - 37
IEEE Solid-State Circuits Magazine - Summer 2017 - 38
IEEE Solid-State Circuits Magazine - Summer 2017 - 39
IEEE Solid-State Circuits Magazine - Summer 2017 - 40
IEEE Solid-State Circuits Magazine - Summer 2017 - 41
IEEE Solid-State Circuits Magazine - Summer 2017 - 42
IEEE Solid-State Circuits Magazine - Summer 2017 - 43
IEEE Solid-State Circuits Magazine - Summer 2017 - 44
IEEE Solid-State Circuits Magazine - Summer 2017 - 45
IEEE Solid-State Circuits Magazine - Summer 2017 - 46
IEEE Solid-State Circuits Magazine - Summer 2017 - 47
IEEE Solid-State Circuits Magazine - Summer 2017 - 48
IEEE Solid-State Circuits Magazine - Summer 2017 - 49
IEEE Solid-State Circuits Magazine - Summer 2017 - 50
IEEE Solid-State Circuits Magazine - Summer 2017 - 51
IEEE Solid-State Circuits Magazine - Summer 2017 - 52
IEEE Solid-State Circuits Magazine - Summer 2017 - 53
IEEE Solid-State Circuits Magazine - Summer 2017 - 54
IEEE Solid-State Circuits Magazine - Summer 2017 - 55
IEEE Solid-State Circuits Magazine - Summer 2017 - 56
IEEE Solid-State Circuits Magazine - Summer 2017 - 57
IEEE Solid-State Circuits Magazine - Summer 2017 - 58
IEEE Solid-State Circuits Magazine - Summer 2017 - 59
IEEE Solid-State Circuits Magazine - Summer 2017 - 60
IEEE Solid-State Circuits Magazine - Summer 2017 - 61
IEEE Solid-State Circuits Magazine - Summer 2017 - 62
IEEE Solid-State Circuits Magazine - Summer 2017 - 63
IEEE Solid-State Circuits Magazine - Summer 2017 - 64
IEEE Solid-State Circuits Magazine - Summer 2017 - Cover3
IEEE Solid-State Circuits Magazine - Summer 2017 - Cover4
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2023
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2023
https://www.nxtbook.com/nxtbooks/ieee/mssc_spring2023
https://www.nxtbook.com/nxtbooks/ieee/mssc_winter2023
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2022
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2022
https://www.nxtbook.com/nxtbooks/ieee/mssc_spring2022
https://www.nxtbook.com/nxtbooks/ieee/mssc_winter2022
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2021
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2021
https://www.nxtbook.com/nxtbooks/ieee/mssc_spring2021
https://www.nxtbook.com/nxtbooks/ieee/mssc_winter2021
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2020
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2020
https://www.nxtbook.com/nxtbooks/ieee/mssc_spring2020
https://www.nxtbook.com/nxtbooks/ieee/mssc_winter2020
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2019
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2019
https://www.nxtbook.com/nxtbooks/ieee/mssc_2019summer
https://www.nxtbook.com/nxtbooks/ieee/mssc_2019winter
https://www.nxtbook.com/nxtbooks/ieee/mssc_2018fall
https://www.nxtbook.com/nxtbooks/ieee/mssc_2018summer
https://www.nxtbook.com/nxtbooks/ieee/mssc_2018spring
https://www.nxtbook.com/nxtbooks/ieee/mssc_2018winter
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_winter2017
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_fall2017
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_summer2017
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_spring2017
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_winter2016
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_fall2016
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_summer2016
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_spring2016
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_winter2015
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_fall2015
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_summer2015
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_spring2015
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_winter2014
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_fall2014
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_summer2014
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_spring2014
https://www.nxtbookmedia.com