HT8691R
内置 BOOST 升压 D/AB 类音频功率放大器
内置BOOST升压和防破音功能的11W D/AB类音频功率放大器
◼ 特点
・小尺寸LCD电视/监视器
◼ 概述
・防削顶失真功能(防破音, Anti-Clipping Function,
ACF)
・免滤波器数字调制，直接驱动扬声器
・输出功率
9.0W (VBAT=3.7V, PVDD = 7.5V, RL=3Ω,
THD+N=10%)
11.0W (VBAT=3.7V, PVDD = 7.5V, RL=2Ω,
THD+N=10%
5.5W (VBAT=3.7V, PVDD = 6.5V, RL=4Ω,
THD+N=10%)
3.15W (VBAT=3.7V, PVDD = 7.5V, RL=8Ω,
THD+N=1%)
・电源
-升压输入VBAT：2.5V至5.5V
-升压输出PVDD：VBAT至7.5V
・BOOST输出电压可调
・AB/D类可切换
・保护功能:过流/过热/欠压异常保护功能
・无铅封装， SOP8L-PP
HT8691R是一款内置BOOST升压模块的D类音
频功率放大器。内置的BOOST升压模块可通过外置
电阻调节升压值，即使是锂电池供电，在升压至7.5V，
2Ω负载条件下则能连续输出11W功率。其支持外部
设置调节BOOST输出电压。
HT8691R的最大特点是防削顶失真（ACF）输
出控制功能，可检测并抑制由于输入音乐、语音信号
幅度过大所引起的输出信号削顶失真（破音），也能
自适应地防止在BOOST升压电压下降所造成的输出
削顶，显著提高音质，创造非常舒适的听音享受，并
保护扬声器免受过载损坏。同时芯片具有ACF-Off 模
式。
HT8691R具有AB类和D类的自由切换功能，在
受到D类功放EMI干扰困扰时，可随时切换至AB类音
频功放模式。
HT8691R内部集成免滤波器数字调制技术，能
够直接驱动扬声器，并最大程度减小脉冲输出信号的
失真和噪音。输出无需滤波网络，极少的外部元器件
节省了系统空间和成本，是便携式应用的理想选择。
◼ 应用
・蓝牙音箱
・2.1声道小音箱
・iphone/ipod/ipod docking
・平板电脑，笔记本电脑
・便携式游戏机
・便携式音箱
・扩音器
・MP4, 导航仪
・智能手机
此外，HT8691R内置的关断功能使待机电流最
小化，还集成了输出端过流保护、片内过温保护和电
源欠压异常保护等功能。
◼ 典型应用图
Dx
10 µF
Battery
1 µF
2
470 µF
LX
HT8691R PVDD
3
1µF 10 µF
470 µF
Rd1
1Ω
FB
1nF
1
Rd2
CTRL
1KΩ
8
CIN
R IN
6
CIN
R IN
7
版权所有©2019, 嘉兴禾润电子科技有限公司
3.3nF
9-GND
IN+
OUT+
IN-
OUT-
-1-
5
4
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
◼ 引脚信息
FB
LX
PVDD
1
8
2
7
9-GND
3
CTRL
IN-
6
IN+
4
5
OUT-
OUT+
SOP8L-PP Top View
◼ 引脚定义1
SOP
Terminal
No.
1
2
3
4
5
6
7
8
9
Name
I/O
ESD
Protection
FB
LX
PVDD
OUTOUT+
IN+
INCTRL
GND2
I
I
Power
O
O
I
I
I
GND
PN
PN
PN
PN
PN
PN
Function
升压反馈点
升压整流管输入
升压输出和功率电源
输出负端l(BTL-)
输出正端(BTL+)
输入正端 (differential +)
输入负端 (differential -)
模式控制输入端
电源地
◼ 订货信息
1
2
产品型号
封装形式
顶面标记
工作温度范围
包装和最小起订量
HT8691RSPET
SOP8L-PP
HT8691RSP
-40℃～85℃
料管 /100颗
HT8691RSPER
SOP8L-PP
HT8691RSP
-40℃～85℃
编带 / 2500颗
I: 输入端 O: 输出端
请确保 GND 脚连接至电源地。.
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-2-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
11W Anti-Clipping Mono Class D/AB Audio Amplifier with
Boost Converter
◼ FEATURE
・LCD TV/Monitor
・Anti-Clipping Function (ACF)
◼ GENERAL DESCRIPTION
HT8691R integrates a boost converter with a
filter-less stereo class D audio power amplifier to
provide 11W continuous power into a 2Ω speaker
when operating from a Li-battery voltage boosted
to 7.5V. Meanwhile, the boost output voltage is
adjustable.
HT8691R features Anti-Clipping Function
(ACF) which detects output signal clip due to the
over input signal and suppresses the output signal
clip automatically. Also, the ACF function can adapt
the output clip caused by power supply voltage
down with battery. It can significantly improve the
sound quality, creating a very comfortable musical
enjoyment, and to protect the speakers from
overload damage. It also supplies ACF OFF mode.
Class AB amplifier mode is also available for
HT8691R. Once the EMI Interference from class D
and Boost Converter becomes an annoying
problem, HT8691R can be changed into Class AB
mode.
HT8691R has a filter-less modulation circuit
which directly drives speakers while realizes low
distortion and low noise characteristics. Thanks to
filter-less, circuit design with fewer external parts
can be made in portable applications.
HT8691R has the independent Shutdown
function which can minimize the power
consumption at standby and MUTE function. As for
protection function, over current protection function
for speaker output terminals, over temperature
protection function, and low supply voltage
malfunction preventing function are also prepared.
・Filter-less Modulation, Eliminating Output Filter
・Output Power
9.0W (VBAT=3.7V, PVDD = 7.5V, RL=3Ω,
THD+N=10%)
11.0W (VBAT=3.7V, PVDD = 7.5V, RL=2Ω,
THD+N=10%
5.5W (VBAT=3.7V, PVDD = 6.5V, RL=4Ω,
THD+N=10%)
3.15W (VBAT=3.7V, PVDD = 7.5V, RL=8Ω,
THD+N=1%)
・Power Supply
-Boost Input VBAT：2.5V to 5.5V
-Boost Output PVDD：VBAT to 7.5V
・Adjustable BOOST Output Voltage
・Class AB / Class D
・Over Current Protection, Thermal Protection,
Low voltage malfunction prevention function
included
・Pb-Free Packages , SOP8L-PP
◼ APPLICATIONS
・Bluetooth Speakers
・Portable Speakers
・2.1 Channel Speakers
・Megaphone
・iphone/ipod/ipod docking
・MP4/GPS
・Tablet PC/Note Book
・Smart Phones
・Portable Gamers
◼ TYPICAL APPLICATION
Dx
10 µF
Battery
1 µF
2
470 µF
LX
HT8691R PVDD
3
1µF 10 µF
470 µF
Rd1
1Ω
FB
1nF
1
Rd2
CTRL
1KΩ
8
CIN
R IN
6
CIN
R IN
7
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
3.3nF
9-GND
IN+
OUT+
IN-
OUT-
-3-
5
4
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
◼ TERMINAL CONFIGURATION
FB
LX
PVDD
1
8
2
7
9-GND
3
CTRL
IN-
6
IN+
4
5
OUT-
OUT+
SOP8L-PP Top View
◼ TERMINAL FUNCTION 1
SOP
Terminal
No.
1
2
Name
I/O
ESD
Protection
FB
LX
I
I
PN
-
3
PVDD
Power
PN
4
5
6
7
8
9
OUTOUT+
IN+
INCTRL
GND2
O
O
I
I
I
GND
PN
PN
PN
PN
Function
Regulator Feedback Input
Internal Switch Input
Boost Converter Output Voltage and Power
Supply
Negative Output Terminal (BTL-)
Positive Output (BTL+)
Positive Input Terminal (differential +)
Negative Input Terminal (differential -)
Mode Control Terminal
Power Ground
◼ ORDERING INFORMATION
1
2
Part Number
Package Type
Marking
Operating
Temperature Range
MOQ/Shipping Package
HT8691RSPET
SOP8L-PP
HT8691RSP
-40℃～85℃
100PCS / Tube
HT8691RSPER
SOP8L-PP
HT8691RSP
-40℃～85℃
2500PCS / Tape and Reel
I: Input
O: Output
Do make sure that the GND pin is grounded into the Ground plane connecting into the power ground.
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-4-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
⚫
ELECTRICAL CHARACTERISTIC
⚫ Absolute Maximum Ratings1
Item
BOOST converter output voltage and Power supply voltage
range
Input terminal voltage range (IN+, IN-)
Symbol
Min.
Max.
Unit
PVDD
-0.3
7.8
V
VIN
－0.6
PVDD＋0.6
V
Input terminal voltage range (except IN+, IN-)
VIN
－0.3
PVDD＋0.3
V
Operating Ambient Temperature
TA
-40
85
℃
Junction Temperature
TJ
-40
150
℃
Storage Temperature
TSTG
-50
150
℃
⚫ Recommended Operating Condition
Item
BOOST converter output voltage and Power
supply voltage range2
Operating Ambient Temperature
Symbol
Conditions
PVDD
Ta
Speaker Impedance
RL
Min.
Typ.
Max.
Unit
VBAT
6.5
7.5
V
-40
25
85
℃
SOP8L-PP
Ω
4
⚫ Electrical Specification3
Item
BOOST Converter
Boost converter output
voltage
Boost converter
frequency
Boost converter input
current limit
Item
Symbol
Conditions
PVDD
Min.
Typ.
Max.
Unit
VBAT
6.5
7.5
V
fSW
410
kHz
ILIMTRIP
5
A
Symbol
Conditions
Min.
Typ.
Max.
Unit
Class D Channel VSS=0V, VBAT =3.7V, RIN = 0ohm, Ta=25ºC, CIN=2.2uF, ACF-Off mode, unless otherwise specified
Carrier clock frequency
fPWM
Over current protection
Imax
System Gain
Start-up time (power-on
or shutdown release)
ACF attenuation gain
Consumption current in
shutdown mode
Total Harmonic
Distortion plus Noise
Av0
410
kHz
6
External RIN=0Ω
tSTUP
Aa
A
28
dB
130
ms
-16
0
dB
ISD
CTRL=VSS
7
µA
THD+N
PO=1.0W, RL=4Ω, f=1kHz
0.10
%
Output Noise
VN
f=20Hz~20kHz, A weighted,
Av=28dB
135
µVrms
Output offset voltage
VOS
±2
mV
Quiescent current
IBAT
20
mA
20
mA
No Load
With Load4
Input Grounded,
PVDD = 6.5V
1
Absolute Maximum Ratings is values which must not be exceeded to guarantee device reliability. With a system in which
supply voltage might exceed supply voltage of PVDD/GND, external diodes are recommended to be used to assure that the
voltage does not exceed the absolute maximum rating
2 The rising time of PVDD should be more than 1µs.
3 Depending on parts and pattern layout, characteristics may be changed.
4
4ohm resistor and 22uH coil are used as an output load in order to simulate a speaker.
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-5-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
Item
Symbol
Conditions
Min.
Typ.
Max.
Class D Channel PVDD = 6.5V VSS=0V, VBAT =3.7V, RIN = 0ohm, Ta=25ºC, CIN=2.2uF, ACF-Off mode, unless
otherwise specified
RL=4Ω
5.5
V
BAT
=3.7V,
RL=3Ω
7
f=1kHz,
RL=2Ω+33uH
9
THD+N=10%
Output Power
PO
RL=8Ω
3.1
RL=4Ω
4.4
RL=3Ω,
RL=2Ω+33uH
Efficiency (Class D +
Boost)
η
VBAT=3.7V,
f=1kHz,
THD+N=1%
RL=8Ω
VBAT=4.2V, RL=4Ω, THD+N =
10%
VBAT=4.2V, RL=3Ω, THD+N =
10%
VBAT=4.2V, RL=2Ω+33uH,
THD+N = 10%
VBAT=4.2V, RL=8Ω+33uH,
THD+N = 10%
W
5.5
5.5
2.5
75
%
70
%
66
%
80
%
Item
Symbol
Conditions
Min.
Typ.
Max.
Class D Channel PVDD = 7.0V VSS=0V, VBAT =3.7V, RIN = 0ohm, Ta=25ºC, CIN=2.2uF, ACF-Off mode, unless
otherwise specified
RL=4Ω
6.2
VBAT=3.7V,
RL=3Ω
Output Power
PO
RL=2Ω+33uH
RL=4Ω
RL=3Ω,
Efficiency (Class D +
Boost)
η
f=1kHz,
THD+N=10%
VBAT=3.7V,
f=1kHz,
THD+N=1%
RL=2Ω+33uH
VBAT=4.2V, RL=4Ω, THD+N =
10%
VBAT=4.2V, RL=3Ω, THD+N =
10%
VBAT=4.2V, RL=2Ω+33uH,
THD+N = 10%
Efficiency (Class D +
Boost)
η
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-6-
Unit
7.6
9.5
W
5.1
6.2
7.5
73
%
69
%
66
%
Item
Symbol
Conditions
Min.
Typ.
Max.
Class D Channel PVDD = 7.5V VSS=0V, VBAT =3.7V, RIN = 0ohm, Ta=25ºC, CIN=2.2uF, ACF-Off mode, unless
otherwise specified
RL=8Ω
3.9
VBAT=3.7V,
RL=4Ω
7
f=1kHz,
RL=3Ω
9
THD+N=10%
RL=2Ω+33uH
11
Output Power
PO
RL=8Ω
3.15
V
BAT
=3.7V,
RL=4Ω
5.5
f=1kHz,
RL=3Ω,
7
THD+N=1%
RL=2Ω+33uH
VBAT=4.2V, RL=8Ω, THD+N =
10%
VBAT=4.2V, RL=4Ω, THD+N =
10%
VBAT=4.2V, RL=3Ω, THD+N =
10%
VBAT=4.2V, RL=2Ω+33uH,
THD+N = 10%
Unit
Unit
W
8.8
82
72
%
68
66
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
Class AB Channel
1
VSS=0V, VBAT =3.6V, CIN = 2.2uF, RIN = 0ohm, Ta=25ºC, CIN=0.1uF, unless otherwise specified
RL=4Ω,
1.3
W
VBAT=3.6V
RL=4Ω,
f=1kHz,
1.8
VBAT=4.2V
THD+N=10%
RL=4Ω,
2.65
W
VBAT=5.0V
Output Power
PO
RL=4Ω,
1.0
W
VBAT=3.6V
RL=4Ω,
f=1kHz,
1.5
W
VBAT=4.2V
THD+N=1%
RL=4Ω,
2.1
W
VBAT=5.0V
PO=0.01W
0.1
%
Total
Harmonic
RL=4Ω,
THD+N
Distortion plus Noise
f=1kHz
PO=0.1W
0.09
%
Output Noise
VN
f=20Hz~20kHz, A weighted
Signal to Noise Ratio
SNR
A weighted, THD+N = 1%
Output offset voltage
VOS
η
Efficiency
Quiescent current
IBAT
System Gain
Start-up time
(power-on, shutdown
release, or switch from
Class D to Class AB)
Av0
Item
60
92
dB
±4
mV
RL=4Ω+22uH, THD+N = 10%
70
%
RL=8Ω+33uH, THD+N = 10%
74.5
%
20
mA
20
mA
22
dB
130
ms
No Load
With Load
Input
Grounded
External RIN=0Ω
tSTUP
Symbol
µVrms
Conditions
CTRL Terminal Voltage
ACF Off (Class D,
Boost On) mode setting
VMOD1
threshold voltage
ACF-1 (Class D, Boost
On) mode setting
VMOD2
threshold voltage
ACF Off (Class AB,
Boost Off) mode setting
VMOD3
threshold voltage2
SD mode setting
VMOD4
threshold voltage
SD wake up voltage
VCTRL_ON
Min.
Max.
Unit
2.4
VBAT
V
1.6
2.2
V
0.4
1.4
V
VSS
0.2
V
0.8
Typ.
1.0
V
Internal pull-down
Resistor of CTRL
RCTRL
300
KΩ
MISCELLANEOUS
VBAT start-up threshold
voltage
VBAT shut-down
threshold voltage
VUVLH
2.5
V
VUVLL
2.0
V
1
In Class AB amplifier mode, boost converter is shutdown automatically. Due to the schottky rectifier, the voltage of PVDD terminal can be
lower than VBAT, depending on the forward voltage of the rectifier VF.
2 ACF ON mode is only available in Class D amplifier mode.
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-7-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
◼ TYPICAL OPERATING CHARACTERISTICS
Class D Channel
Condition: Class D mode, VBAT = 3.7V, fIN = 1kHz, CIN = 2.2uF, external RIN = 0ohm, ACF off, unless otherwise specified
PVDD = 7.5V, Load = 4ohm
Output Power vs THD+N
fIN vs THD+N
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-8-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
Audio Precision
PVDD
= 7.5V, Load = 8ohm
12/29/20 09:45:40
20
10
5
2
1
%
0.5
0.2
0.1
0.05
0.02
0.01
10m
20m
50m
100m
200m
500m
1
2
5
W
Audio Precision
Sweep
11
12/29/20 10:04:05
Trace
Color
Line Style
Thick
Data
Axis
1
Red
Solid
2
Analyzer.THD+N Ratio A
Left
5
Po vs THD+N.ats2
0.9
%
Comment
4.5
0.8
4
0.7
3.5
0.6
3
0.5
2.5
0.4
2
0.3
W
1.5
0.2
1
0.1
500m
20
50
100
200
500
1k
2k
5k
10k
20k
Hz
Sweep
Trace
Color
Line Style
Thick
Data
Axis
1
1
1
2
Red
Green
Solid
Solid
2
2
Analyzer.THD+N Ratio A
Analyzer.Level A
Left
Right
Comment
f vs THD+N.ats2
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-9-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
PVDD = 7.5V, Load = 3ohm
Output Power vs THD+N
fIN vs THD+N
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-10-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
PVDD = 7.5V, Load = 2ohm+33uH
Output Power vs THD+N
fIN vs THD+N
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-11-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
PVDD = 7.0V, Load = 4ohm
Output Power vs THD+N
fIN vs THD+N
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-12-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
PVDD = 7.0V, Load = 3ohm
Output Power vs THD+N
fIN vs THD+N
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-13-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
PVDD = 7.0V, Load = 2ohm+33uH
Output Power vs THD+N
fIN vs THD+N
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-14-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
Frequency Respond
Input Voltage Level vs Output Voltage Level (PVDD = 7.5V, Load = 4ohm)
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-15-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-16-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-17-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-18-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
Class AB Channel
Condition: Class AB mode, VBAT = 3.7V, fIN = 1kHz, CIN = 2.2uF, external RIN = 0ohm, Load = 4ohm, unless otherwise
specified
Load = 4ohm
Output Power vs THD+N
fIN vs THD+N
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-19-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
Load = 3ohm
Output Power vs THD+N
fIN vs THD+N
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-20-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
Load = 2ohm+33uH
Output Power vs THD+N
fIN vs THD+N
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-21-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
Frequency Respond (RIN = 0ohm)
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-22-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-23-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
◼ APPLICATION INFORMATION
⚫ BOOST Converter
(1) Setting Output Voltage
The output voltage is set by a resistive voltage divider from the output voltage to FB terminal, which is
shown below. The output voltage can be calculated by PVDD = 1.24*(Rd1+Rd2)/Rd2.
Cd2
Rd1
PVDD
Rd2
FB
Fig. 1 FB Terminal Configuration
Some typical output voltages can be got by following settings.
Table 1. Output Voltage Setting
PVDD
5.0V
6.5V
7.0V
7.5V
Rd1
510K
510K
510K
510k
Rd2
165K
120K
110K
100k
Cd2
3.3nF
3.3nF
3.3nF
3.3nF
(2) LX Terminal
It is strongly recommended to place an RC circuit from the terminal of LX to Ground, shown as following, so
that the ripple current of Boost Converter can be decreased. Meanwhile, the total consumption current of
the system will be larger so that the efficiency of the system will be lower. Specifications in this file is
measured under the condition with RC.
Notes: RC should be placed as closely to LX pin as possible.
LX
RLX
1Ω
CLX
1nF
Fig. 2 LX Terminal Configuration
(3) Capacitor Selection
The input and output capacitor (CIN and COUT) is required to maintain the DC voltage. Low ESR capacitors
are preferred to reduce the output voltage ripple. 1uF//10uF//220uF (paralleled) is highly recommended to
be placed in both input and output terminal as closely to the pin as possible. If possible, 470uF is better
than 220uF.
(4) Inductor Selection
The inductor is selected based on different conditions. Normally, L≥2.2uH, DCR 12V, VFM＜0.5V, and do make sure that IF is higher than the maximum current of output power
supply.
(6) Layout Consideration
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
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12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
1. The power traces, consisting of the GND, LX, VBAT and PVDD trace should be kept short, direct, wide,
and as closely to the pin as possible. The switching node LX should be paid more attention for EMI and
reliability consideration.
2. Place CIN and COUT near VBAT and PVDD as closely as possible to maintain voltage steady, and filter
out the pulsing current.
3. The resistive divider R should be connected to pin directly as closely as possible. FB is a sensitive
node. Please keep it away from switching node, LX.
4. The GND of the IC, CIN and COUT should be connected close together directly to ground plane.
⚫ Analog Signal Input Configuration
HT8691R is an amplifier with analog input (single-ended or differential). For a differential operation, input signals
into IN+ and IN- pins via DC-cut capacitors (CIN) and external input resistors RIN. The input signal gain is
calculated by Gain RF (External RIN +Internal RIN ) . And the high pass cut-off frequency of input signal can be
calculated by
.
For a single-ended operation, input signals to IN+ pin via a DC-cut capacitor (CIN) and external input resistor
(RIN). IN- pin should be connected to ground via a DC-cut capacitor and external input resistor (RIN) (with the
same value of CIN and RIN). The Gain and high pass Cut-off frequency are the same as the above case.
Table. 2
Internal input resistors and feedback resistors
Working Mode
Class D mode
Class AB mode
Front Circuit
Internal RIN(ohm)
17.8k
17.8k
Front Circuit
HT8691R
IN+
ZOUT
CIN
External
RIN
RF(ohm)
450K
225K
HT8691R
IN+
ZOUT
Internal
RIN
CIN
External
RIN
IN-
Internal
RIN
IN-
Fig. 3 (1) Differential Input;
(2) Single-ended Input
⚫ Output Configuration
As mentioned, HT8691R can directly drive speakers without any other components. But there are
exceptions. Once HT8691R works in class D mode, the cable lined to the speaker is very long, and EMI is
concerned, ferrite beads or L-C filter is needed.
⚫ CTRL Terminal Mode Control
HT8691R can work in different modes by setting the CTRL terminal, shown as follow.
Table. 3
CTRL Terminal Mode Control
MODE
SYMBOL
Class D mode in ACF-Off with Boost
Converter
Class D mode in ACF-ON with Boost
Converter
Class AB mode in ACF-Off without Boost
Converter
SD(Shutdown) Mode
MIN.
CTRL Voltage
TYP.
MAX.
UNIT
VMOD1
2.4
VBAT
V
VMOD2
1.6
2.2
V
VMOD3
0.4
1.4
V
VMOD4
VSS
0.2
V
Notes: ACF-ON mode can only be worked in class D mode. A 300kΩ pull-down resistor are inside of the
CTRL terminal, shown as follows.
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
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12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
HT8691
300KΩ
CTRL
Fig. 4 CTRL Terminal
HT8691R can only be turned into operation from shutdown mode when the voltage of CTRL is
higher than 0.8V (1.0V is recommended).
⚫ Anti-Clipping Function (ACF) and mode Configuration
(1) ACF ON Mode
In ACF-ON modes, HT8691R attenuates system gain to an appropriate value when an excessive input is applied,
so as not to cause the clipping at the differential signal output. In this way, the output audio signal is controlled in
order to obtain a maximum output level without distortion. And HT8691R also follows to the clips of the output
waveform due to the decrease in the power-supply voltage.
(1) Excessive Inputs
Input
Initial Gain
Av0
Total
Gain
ACF ON
Peak -
Av=Av0+Aa
Attack Time
Excessive
Inputs
Peak +
Clipping
Detection
Release Time
ACF OFF
Peak +
ACF
Attenuation
Gain
Peak -
-10dB≤Aa≤0
(2) Appropriate inputs
Initial Gain
Av0
Power Supply
Decreasing
Total
Gain
ACF ON
+
+
PVDD
Decrease
-
Av=Av0+Aa
Clipping
Detection
Attack Time
Release Time
ACF
Attenuation
Gain
-10dB≤Aa≤0
Fig. 5 the ACF Function Operation Outline
The Attack time of ACF Function is a time interval until system gain falls to target attenuation gain -3dB when a
big enough signal input. And, the Release Time is a time from target attenuation gain to not working of ACF. The
maximum attenuation gain is 16dB.
Table 4 Attack time and Release time
ACF mode
ACF ON
(2) ACF OFF Mode
Attack time
Release time
50ms
64ms
In ACF-Off mode, ACF function is disenabled. HT8691R will not detect output clipping and the system gain is
kept to be Av=Av0. The audio quality would worsen due to clipping distortion.
(3) Class AB mode
HT8691R works as Class AB audio Amplifier in ACF off mode, the boost converter is disenabled.
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
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12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
(4) SD Mode
In shutdown mode, HT8691R shuts all circuit down and minimizes the power consumption. And, the output
terminals become Weak Low (A high resistance grounded state).
⚫ Pop-Click Noise Reduction
The Pop-Click Noise Reduction Function of HT8691R works in the cases of Power-on, Power-off, Shutdown on,
and Shutdown off. To achieve a more excellent noise reduction performance, it is recommended to use a DC-cut
capacitor (CIN) of 0.1µF or less.
Besides, POP noise can be minimal according to the following procedure of shutdown control.
・During power-on, Shutdown mode is not cancelled until the power supply is stabilized enough.
・Before Power-off, set Shutdown mode first.
The pop-click noise: Power-on/-off > Shutdown on/off.
tDELAY>tSTUP
VBAT
tDELAY>50ms
VUVLH
VUVLL
ACF-Off
ACF-On
ClassAB
CTRL
SD
tSTUP
OUT
Power off
SD
Operation
SD
Power off
Fig. 6 Pop-Click Noise Reduction by Shutdown
⚫ Protection Function
HT8691R has the protection functions such as Over-Current Protection function, Thermal Protection function,
and Low Voltage Malfunction Prevention function.
(1) Over-current Protection function
When a short circuit occurs between one output terminal and Ground, PVDD, or the other output, the
over-current protection mode starts up. In the over current protection mode, the differential output terminal
becomes a high impedance state. Once the short circuit conditions are eliminated, the over current protection
mode can be cancelled automatically.
(2) Thermal Protection function
When excessive high temperature of HT8691R (150℃) is detected, the thermal protection mode starts up. In the
thermal protection mode, the differential output terminal becomes Weak Low state (a state grounded through
high impedance).
(3) Low voltage Malfunction Prevention function
This is the function to establish the low voltage protection mode when PVDD terminal voltage becomes lower
than the detection voltage (VUVLL) for the low voltage malfunction prevention. And the protection mode is
canceled when PVDD terminal voltage becomes higher than the threshold voltage (V UVLH). In the low voltage
protection mode, the differential output pin becomes Weak Low state (a state grounded through high impedance).
HT8691R will start up within the start-up time (TSTUP) when the low voltage protection mode is cancelled
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-27-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
⚫ PCB Layout
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-28-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
◼ PACKAGE OUTLINE
Copyright ©2019, Jiaxing Heroic Technology Co., Ltd
-29-
12/2020 – V1.3
HT8691R
Class D/AB Audio Amplifier
IMPORTANT NOTICE
注意
Jiaxing Heroic Electronic Technology Co., Ltd (HT) reserves the right to make corrections, modifications, enhancements,
improvements, and other changes to its products and services at any time and to discontinue any products or services.
Customers should obtain the latest relevant information before placing orders and should verify that such information is
current and complete.
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提供任何产品和服务的权利。客户在下单和生产前应确保所得到的信息是最新、最完整的。
HT assumes no liability for applications assistance or customer product design. Customers are responsible for their
products and applications using HT components.
HT对相关应用的说明和协助以及客户产品的板级设计不承担任何责任。
HT products are not authorized for use in safety-critical applications (such as life support devices or systems) where a
failure of the HT product would reasonably be expected to affect the safety or effectiveness of that devices or systems.
HT的产品并未授权用于诸如生命维持设备等安全性极高的应用中。
The information included herein is believed to be accurate and reliable. However, HT assumes no responsibility for its
use; nor for any infringement of patents or other rights of third parties which may result from its use.
本文中的相关信息是精确和可靠的，但HT并不对其负责，也不对任何可能的专利和第三方权利的侵害负责。
Following are URLs and contacts where you can obtain information or supports on any HT products and application
solutions:
下面是可以联系到我公司的相关链接和联系方式：
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Jiaxing Heroic Electronic Technology Co., Ltd.
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Add:
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12/2020 – V1.3
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