■山东临沂师范学院物理与电子科学系 马存 云
山 东 大 学 电 子 工 程 系 范坤泰
B^sH① 功率放大 器芯 片 sT^575
立 体声
STA57⒌ Stcrcophonic Sound BASHR Powcr Amp
"认
:的 -利 IAC
Vin(pCak)=± 8ˇ 鼓 大 峰 ″i输 入 lL流
也 Ij古 |顷 输 人信 1∫ jLFk电 lF和
AB类 输 出并 勹数宁处胛器
575足 ST公 i刂
i户
IC订 却 17
Iin(pcak)=⊥ ImA,丿 k缩 器输 人 闸 限 屯
、
STABPOl结 合使川的 一种宀效衤和冖
叮
丨
J咱 订衤片如衍 、闸阝
丿
【V1h亻 i关。Fl9芒
k【 匕
k Vl"R⒈ s"=^5~0Y〗 却 stby/Mutc I吐 大
丿
J宀 丿
贡讧丨
本声f BAsH°
输人
助1I辶 丿 l|l,电 路 的 约 束 条 件 为 V山 =
-5~0ˇ 山t人 输 人 峰 位 电 丿
k Vinpk
'丨
耦合输 人
J力
氵
攵丿cP挎 丿
芯片∷
钌方
l匕
/人
l丨
流 Istby(n1ax)=200卜 1A, Ⅱ作
Jl吐 竞汛
Il∫ 攴
Tamb=o~70℃ ∶
(nla x)=8V 仃不「
J(Vth下 ,∫ 【
刂门限电丿
j输 人电丿
k巾 Ⅰ
缩 器哀减 丨
i￠ I Ⅵ npk之 问
=
功 能与工作原 理
关 系如囡 2所 尔
sTA575柒 成 r构 筑 ψ
l/lx丿
功衤放 人糌所必需 的电路 ∵何 一
l;缩 后 的仁i盱 进衍
绝 对仃i屯 路 对∫
个讪 逆 以 输 出电桥 功 率放 大 料
检波,以 为外 邮数宁变换 糌提供控制电
忙缩 Ij检 波 电
l1础 ,丨 时加进 丿
为丿
k=Jt输 ∫
||电 丿
丿
i:樱 巾
∴
i丫
￡
各和吒笊 电l符 Ⅱ
/l|9辶
礻
年 丨 ‘
丨
i刂
lxl闸
l/、
rl∶
1.工 作 模 式 设 定
止
川
u ll
方
色力
"J IC
Mutc)的 电压决定
图
)叮
l sTA575芯 片 电路 纽 成 框 图
V脚
IC I∶ 作状态
:
大糌,i刂 以J沪 端连接到古频亻
f号 的差分
氵
:'朽k
变换 .— 个放大糌采川 冂桕拓朴 ,增 益
l丨 :'丬
'人
"(08V时 ,lC进
足 ⒉ 另
蚺荣
P丶
刂
〓`^
封装 。它在芯片上集成 了预放大搽输人
静噪抑制 (无 声 )模 式 ,扬 声器输 出降
・
s
级 、外部可编程反饶 型压缩搽 、绝对 t1
为地 电位 。当 IC检 测到危险情况时 ,脚
12
11内 的开/关 时序 电路迫使
IC迅 速进
ˉ
1B
检波 电路 、输 出电桥放大器 、接通/关
断时序 电路及安仝 I作 区 (sOA)、 过
人待机模式或 静噪抑制状态。
人待机模式,与 估号逦路有关的所亻j电
1所 示 。
为防止 大功率 消耗 和信号削波失
真 ,sTA575的 压缩器电路对 输入∫
;号
言
下 的输 出功率 为 75W× 2,在 Rl=8Ω 和
T缩 。输人端预放大器的电压增益
进行丿
|∶
l∶
竹:范 |Ⅱ 限制 r[分 别为
i
丨
:Vs=-10~24V,山 t人 山
电丿
【
帑″i愉 人电丿
加 侈 竹
唧
岬
“ ″略
5
6
7
压缩 器哀减与输入电压幅值之问关系
刂
luM甲
{[{、 ;1传
,
编TJ反 dtI【 刂 缩 糌
`【
【缩 `"∶ 能实际 ⒈足逦
降低 26dB。 IC的 丿
反馈网纟
过 冫 小夕卜
钥‘
符的Ⅱlllt实 现 的,和
|戈
tr,J’ J
∵卩甲蹿髀胛哪呷猡稗叩W哪 狃晖犟甲Ⅱ暂呷呷叩呷猡唧
Ι
∶
:
l乜 源 丨
Π∶
L川 艹Vs=20~32V负 电祝
γ
=5,在 大 信号输 人或 低 I匕 源 电 ∫【下
J tJ"溢 迪过 外部
lB)
大戊 ・
4
sTΛ 575在 R1=418Ω 和 THD=05%
该糌饣 的
忄 `¨ △攀诨嘿 哪
吖∷
lYl位 增
扭
2,信 号 压 缩
il∫
个采川反桕拓 朴 ,带
,IC进 人
屯压和过热保护 等电路,内 部结构如图
CΓ
14Ⅱ
输 出电桥放 大器利川两 个功率 放
=16~3V时
路关闭 ;当 V脚 ”
100W× 2
被阝
K制 ,增
l lxl邮
却 Stby/
(川
")4V"忄 ,IC进 、
态操作;当 V脚
rl∶
l∶
4.输 出 电桥放大器
封装 、 内部结构 及 电气特性
STA575采 fFl27脚 FLEXIWATT
THD=10%下 的输 出功率达
;
3.绝 对 值 检 波
lf
!
图 3 功率 保护 电路
饣丿
r`k
l序 电路
,’
益 (uni9gain)。 为保证在输 人
闷 定 刂兀 件
夫
刂
‖P、 VR~INPl和 丨P、/R~INP2
Tattack=13nls,平 ∮方
攵 Ⅱ
刂
|丨
有 一 个高输人 阻抗 ,在 每 — 个
(汩
|li|i丨
凵Ⅱ刂
"刂
1△
通道 中的功放级 电路 中,第 工
clcasc=lS)∷ i刂 却6夕 卜
闸‘
丨
乜阻lR1‘ 禾刚却22夕 卜
击丨
乜
|‘
个放大器 由第 一 个放大器的输
阻 R17(均 为 01Ω /4W),
JJ驱 动 。
∞
分 别 是安 伞 丁作
,
5.功 率 保 护
(SOA)检 测器 的电流感
" sTA575
叱
为保护功率桥路的输 出品
测元件 。
脚 16和 ll却
几
体管 ,sTA575内 置功率检波器
CD+
器 sTABpOl捉 供参考和
吣
咖
CD+l与
保护信号 。
m僻
猡
之间连接的电流感测电阻 RsENsE
sTA575与 数字处理
器 sTABP01芯 片结合使
检测 ,同 时内部电路也测量其电
压 降落。检测信号经变换和倍
图4
乘,产 生电流 IPⅡ 并且该电流正
与参考电流 IPM相 比较,当 电流较大时,若
功耗 Pρ 32⒒ 电流 IP巛 订则施加到保护脚
,
以 为数字 变换 器 中处 J驻 器芯 片捉供保
护信号 ,减 小数字变换器输 出级 屯压和
功率消耗 。当 IPD达 到 ^个 较南的门限
P沪 60W)日 寸,经 电流 比较器从 PDP1
输 出到开/关 程序 电路 ,使 芯片关闭。如
果流过限值是 0.1Ω 的
g却
CD"与
`cIlsc电
sTA575的 测 试 与应 用 电路
用 时 的 电路框 图如 图
流达 7A
CD+之 问电丿
i;降 达 07V),
5
丿
9i/J1c sTABPOl丿 Ⅱ
放 大搽 r昀 高效
比于输 出品体管上 的瞬时消耗功率。IPD
(即
12L
的输 出分别 为数字处 理
电路 ,如 图 3所 示 。流过功率电
桥的电流通过脚
I区
li三
Rl和 R2
控制数字变换 器,通 过
为输人电阻
分析 占频输 人,处 理器
率 。
,
R3和 R4是 反 钅
决定适 当的开/关 过稆
馈 电阻,预 放大
为 数 字 变换 器 产 -L数
5
k缩 )的 图
器 (未 丿
阴
As75与
盯
ABPOl救 字 处 理 器 应 用 电 路 框 囚
宁 脉
,
冲 并 咬 换 成 功 率
士
曾益 G=R3/Rl=R4/R2=5okΩ /10kΩ =5。
信号馈送到功率放大器 。反馈 系统 允沟
IC脚 17为 压缩 搽 门 限 电压 输 人 ,脚
处理 器不陶亍
适 应 奸 lfli估 号并Ⅰ
Π彩i产 Ⅱ
ll
外 部 RC网 络 及 开关 用作 决 定 放 大 器 I
作 状 态 。脚 3外 部 的
外部 的
C3和 R5及 脚
25
i
数字脉
, l,N丨
l扌 舯 卜
J七 丫
输 Jll获 得一-彳
`′
}11
`Ⅱ
l;c【
定电丿
"I臼
C4和 R6分 别 为 冲击 和 释 放 时
芯片同样被关 闭。
sTA575内 置热保护电路。当平均
结温达 130℃ ,且 输 出电桥进人 Mu亿
模式或 当平均结温达 150℃ 时,芯 片关
闭。此外 ,当 电源 电压之和 Vs++Vs~
(20V和
在
[(VcDD-(VcD)]/2>5V情
况下 ,芯 片也会关 闭。
摄 琶 ・Γ 百 ・
仁 琶 ・编 查
o2025
姓名:尤 祖茵
职务:工 程师
单位名称:福 建省南平地区电子研究所
:福
179号
地址
建省南平市延平区东山胳
邮编:353000
TeI: 0599ˉ 8833656
Fax: 0559-8849115
我们正在研制或生产的产品是:水 声仪器
需要采购的产品是:密 封防水超声波发射 、接收传感器。
应 用 电路
sTA575的 典型应用及 测试电路如
Vs偏
图 4所 示 。信号电路通过+Vs和 ˉ
置 ,而 输 出放大器最后一级电路通过两
使输 出晶体管保持在最小电平上 ,获 得
娃名:马 金娥
职务:采 购员
地址:北京 28s3信 箱
箱
"分
Tel: 010ˉ 64872754-8o15
单位名称:北 京市环佳通信技术公司
邮编 :100085
Fax: o1o~64872754ˉ 8o01
我们正在研制或生产的产品是:数宇微波、模拟微波、扩频设备、光端机
需采购的产品:高 颁管以及所有器件
【●I∝ 臼
2口 ″.亻
世 界电子元器件
JJ
髑
〓
∷:
∷
∷
∷
〓
一
∷
一
≡
・
∷∷
个外部 电压 (CD+和 CD-)施 加 ,从 而
o2026
缃
STA575
100+100W STEREO
■
■
■
■
■
■
■
■
■
■
POWER AMPLIFIER
MONOCHIP BRIDGE STEREO AMPLIFIER
ON BASH ® ARCHITECTURE
80+80W OUTPUT POWER @ RL = 4/8 Ω,
THD = 0.5%
100+100W OUTPUT POWER @ RL = 4/8 Ω,
THD = 10%
HIGH DYNAMIC PREAMPLIFIER INPUT
STAGES
EXTERNAL PROGRAMMABLE FEEDBACK
TYPE COMPRESSORS
AC COUPLED INPUT TO CLASS AB BRIDGE
OUTPUT AMPLIFIER
PRECISION RECTIFIERS TO DRIVE THE
DIGITAL CONVERTER
ON-OFF SEQUENCE/ TIMER WITH MUTE
AND STANDBY
PROPORTIONAL OVER POWER OUTPUT
CURRENT TO LIMIT THE DIGITAL
CONVERTER
ABSOLUTE POWER BRIDGE OUTPUT
FLEXIWATT27
■
■
■
■
■
TRANSISTOR POWER PROTECTION
ABSOLUTE OUTPUT CURRENT LIMIT
INTEGRATED THERMAL PROTECTION
POWER SUPPLY OVER VOLTAGE
PROTECTION
FLEXIWATT POWER PACKAGE WITH 27 PIN
BASH® LICENCE REQUIRED
DESCRIPTION
The STA575 is a fully integrated power module designed to implement a BASH® amplifier when used
in conjunction with STABP01 digital processor.
BLOCK DIAGRAM
+VS
GND
-VS
OUT_ PRE1
TRK_1
PWR_INP1
ABSOLUTE
VALUE
BLOCK
+
-
CD+1
+2
∆G
IN_PRE1
OUT1+
-1
OUT1-
COMPRESSOR
OUTPUT BRIDGE
CD-1
V/l
ATT_REL1
CD+
PEAK/2
DETECTOR
S1
Ict
VOLTAGE
PROTECTION
Ict
THERMAL
PROTECTION
SOA
DETECTOR
PROT.
TURNON/OFF
SEQUENCE
STBY/MUTE
TRK_OUT
THRESH
PEAK/2
DETECTOR
S1
ATT_REL2
V/l
CD+2
+2
COMPRESSOR
-1
-
ABSOLUTE
VALUE
BLOCK
+
OUT_ PRE2
July 2003
OUT2+
∆G
IN_PRE2
TRK_2
OUT2-
OUTPUT BRIDGE
PWR_INP2
CD-2
D01AU1263
1/20
STA575
DESCRIPTION (continued)
Notice that normally only one Digital Converter is needed to supply a stereo or multi-channel amplifier system,
therefore most of the functions implemented in the circuit have summing outputs
The signal circuits are biased by fixed negative and positive voltages referred to Ground. Instead the final stages of the output amplifiers are supplied by two external voltages that are following the audio signal . In this way
the headroom for the output transistors is kept at minimum level to obtain a high efficiency power amplifier.
The Compressor circuits, one for each channel, performs a particular transfer behavior to avoid the dynamic
restriction that an adaptive system like this requires. To have a high flexibility the attack / release time and the
threshold levels are externally programmable. The tracking signal for the external digital converter is generated
from the Absolute Value block that rectifies the audio signal present at the compressor output. The outputs of
these blocks are decoupled by a diode to permit an easy sum of this signal for the multichannel application. The
output power bridges have a dedicated input pin to perform an AC decoupling to cancel the compressor output
DC offset. The gain of the stage is equal to 4 (+12dB). A sophisticated circuit performs the output transistor power detector that , with the digital converter, reduces the power supply voltage . Moreover, a maximum current
output limiting and the over temperature sensor have been added to protect the circuit itself. The external voltage applied to the STBY/MUTE pin forces the two amplifiers in the proper condition to guarantee a silent turnon and turn-off.
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
Value
Unit
+Vs
Positive supply voltage referred to pin 13 (GND)
30
V
-Vs
Negative supply voltage referred to pin 13 (GND)
-24
V
VCD+
Positive supply voltage tracking rail referred to pin 13 (GND)
22
V
VCD+
Positive supply voltage operated to Vs+(1)
0.3
V
VCD-
Negative supply voltage referred to -Vs (1)
-0.3
V
VCD-
Negative supply voltage tracking rail referred to pin 13 (GND)
-22
V
VAtt_Rel1
VAtt_Rel2
Pin 3, 25 Negative & Positive maximum voltage referred to GND
(pin 13)
-0.5 to +20
V
VPwr_Imp1
VPwr_Imp2
VTrk_1
VTrk_2
Pin 7, 21, 18, 10 Negative & Positive maximum voltage referred to
GND (pin 13)
-20 to +20
V
VIn_pre1
VIn_pre2
Pin 8, 20 Negative & Positive maximum voltage referred to GND
(pin 13)
-0.5 to +0.5
V
Vthreshold
Pin 17 Negative & Positive maximum voltage referred to GND (pin
13)
-7 to +0.5
V
Pin 11 maximum input current (Internal voltage clamp at 5V)
500
µA
Pin 11 negative maximum voltage referred to GND (pin 13)
-0.5
V
Output current
7.7
A
Istb-max
Vstbymute
Iout
Note 1: VCD- must not be more negative than -Vs and VCD+ must not be more positive than +VS
Note 2: All pins withstand ±2KV ESD but not pin 11
2/20
STA575
THERMAL DATA
Symbol
Tj
Parameter
Max Junction temperature
Rth j_case Thermal Resistance Junction to case .............................. ..max
Value
Unit
150
°C
1
°C/W
Value
Unit
OPERATING RANGE
Symbol
Parameter
+Vs
Positive supply voltage
+20 to +28
V
-Vs
Negative supply voltage
-10 to -23
V
5V ≤ (Vs+ - VCD+) ≤ 10V
V
∆Vs+
Delta positive supply voltage
VCD+
Positive supply voltage tracking rail
+3 to 20.7
V
VCD-
Negative supply voltage tracking rail
-20.7 to -3
V
Current at pin In_Pre1, In_Pre2, related to compressor behaviour
-1 to +1
mA peak
Voltage at pin Threshold
-5 to 0
V
Ambient Temperature Range
0 to 70
°C
200
µA
Iin_Max
Vtrheshold
Tamb
Isb_max
Pin 11 maximum input current (Internal voltage clmp at 5V)
PIN CONNECTION
CD-2
OUT2+
ATT_REL2
CD+2
OUT2-
IN_PRE2
PWR_INP2
TRK_2
OUT_PRE2
TRK_OUT
THRESHOLD
+VS
CD+
GND
PROTECTION
TRK_1
STBY/MUTE
IN_PRE1
OUT_PRE1
CD+1
PWR_INP1
OUT1-
OUT1+
ATT-REL1
-VS
CD-1
-Vs
27
1
D01AU1251
Note: Slug connected to pins n. 1 and 27
3/20
STA575
PIN FUNCTION
N°
Name
1
-Vs
2
CD-1
3
Att_Rel1
4
Out1+
Channel 1 speaker positive output
5
Out1-
Channel 1 speaker negative output
6
CD+1
Channel 1 positive power supply
7
Pwr_Inp1
8
In_pre1
9
Out_pre1
10
Trk_1
11
Stby/mute
Standby/mute input voltage control
12
Protection
Protection signal for STABP01 digital processor
13
Gnd
Analog Ground
14
+Vs
Positive Bias Supply
15
CD+
Time varying tracking rail positive power supply
16
Trk_out
Reference output for STABP01 digital processor
17
Threshold
18
Trk_2
19
Out_pre2
20
In_pre2
21
Pwr_Inp2
22
CD+2
Channel 2 positive power supply
23
Out2-
Channel 2 speaker negative output
24
Out2+
Channel 2 speaker positive output
25
Att_Rel2
26
CD-2
27
-Vs
4/20
Description
Negative Bias Supply
Channel 1 Time varying tracking rail negative power supply
Attack release rate for channel 1
Input to channel 1 power stage
Pre-amp input for channel 1 (virtual ground)
Output channel 1 pre-amp
Absolute value block input for channel 1
Compressor threshold input
Absolute value block input for channel 2
Output channel 2 pre-amp
Pre-amp input for channel 2 (virtual ground)
Input to channel 2 power stage
Attack release rate for channel 2
Channel 2 Time varying tracking rail negative power supply
Negative Bias Supply
STA575
ELECTRICAL CHARACTERISTCS (Test Condition: Vs+ = 28V, Vs- = -23V, V CD+ = 20V, VCD- = -20V, RL =
8Ω, external components at the nominal value f = 1KHz, Tamb = 25°C unless otherwise specified
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
9
11
13
Vpeak
0.8
mA
0.65
12
V
V
V
-1
V
PREAMPLIFIER AND COMPRESSOR
Vout clamp Maximum Voltage at Out_pre pin
Iin
Audio input current
Vcontrol
Voltage at Attack_Release pin
Attenuation = 0dB
Attenuation = 6dB
Attenuation = 26dB
0.35
6
0
0.5
9
Th
Input voltage range for the
compression
Zth
Input impedance of Threshold pin
Voffset
Output Offset at Out_pre pin with:
VCRT= 0V; Attenuation = 0dB
VCRT= 0.5V; Attenuation = 6dB
VCRT= 9V; Attenuation = 26dB
THD
Distortion at Out_pre:
VCRT= 0V; Attenuation = 0dB
VCRT= 0.5V; Attenuation = 6dB
VCRT= 9V; Attenuation = 26dB
0.01
EN
Noise at Out_pre pin :
VCRT= 0V; Attenuation = 0dB
VCRT= 0.5V; Attenuation = 6dB
VCRT= 9V; Attenuation = 26dB
10(2)
50
60
Ict
Attack time current at pin
Attack_release
VComp_
-5
100
KΩ
-15
-250
-1000
15
250
450
mV
mV
mV
0.1
0.5
2
%
%
%
µV
µV
µV
0.5
1.5
3
mA
Tracking reference voltage gain
13
14
15
V
Vtrk_out
Tracking ref. output voltage
0
20
Itrk_out
Current capability
5
6
Ztrk_in
Input impedance (TRK1/2)
1. This value is due to the thermal noise of the external resistors Rr and Ri.
TRACKING PARAMETERS
Gtrk
V
7
1
mA
MΩ
OUTPUT BRIDGE
Gout
Half Output bridge gain
5.5
6
6.5
dB
Gch
Output bridge differential gain
11
12
13
dB
∆Gch
Output bridges gain mismatch
-0.5
0.5
dB
Pout
Continuous Output Power
THD
Total harmonic distortion of the
output bridge
THD = 0.5%
THD = 10%
75
95
80
100
W
W
THD = 10%; RL= 4Ω; VCD+ = 16V;
VCD- = -16V; VS+ = 22V; VS- = -22V
90
100
W
Po = 5W
0.01
f = 20Hz to 20KHz; Po = 50W
VOff
Output bridge D.C. offset
-70
0.1
%
0.2
%
70
mV
5/20
STA575
ELECTRICAL CHARACTERISTCS (continued)
Symbol
EN
Parameter
Noise at Output bridge pins
Test Condition
Min.
f = 20Hz to 20KHz; Rg = 50Ω
Typ.
Max.
Unit
µV
12
Zbr_in
Input impedance
Rdson
Output power Rdson
OLG
Open Loop Voltage Gain
100
dB
GB
Unity Gain Bandwidth
1.4
MHz
SR
Slew Rate
8
V/µs
100
IO = 1A
140
180
KΩ
200
400
mΩ
PROTECTION
Vstby
Stby voltage range
0
0.8
V
Vmute
Mute voltage range
1.6
2.5
V
Vplay
Play voltage range
4
5
V
Th1
First Over temperature threshold
130
°C
Th2
Second Over temperature
threshold
150
°C
Unbal.
Ground
Upper Unbalancing ground
threshold
Referred to (CD+ - CD-)/2
5
V
Unbal.
Ground
Lower Unbalancing ground
threshold
Referred to (CD+ - CD-)/2
-5
V
Under voltage threshold
|Vs+| + |Vs-|
18
20
22
V
Pd_reg.
Power dissipation threshold for
system regulation
Iprot = 50µA; @ Vds = 10V
26
32
39
W
Pd_max
Switch off power dissipation
threshold
@ Vds = 10V
60
W
Iprot
Protection current slope
for Pd > Pdreg
400
µA/W
Ilct
Limiting Current threshold
UVth
I+Vs
I-Vs
Positive supply current
Negative supply current
6.3
7
7.5
A
Stby (Vstby/mute pin = 0V)
Mute (Vstby/mute pin = 2.5V)
Play (Vstby/mute pin = 5V no signal)
20
20
5
35
35
7
50
50
mA
mA
mA
Stby (Vstby/mute pin = 0V)
Mute (Vstby/mute pin = 2.5V)
Play (Vstby/mute pin = 5V no signal)
20
20
5
35
35
7
50
50
mA
mA
mA
ICD+
Positive traking rail supply current
Stby (Vstby/mute pin = 0V)
Mute (Vstby/mute pin = 2.5V)
Play (Vstby/mute pin = 5V no signal)
50
60
60
100
110
110
200
180
180
µA
mA
mA
ICD-
Negative traking rail supply current Stby (Vstby/mute pin = 0V)
Mute (Vstby/mute pin = 2.5V)
Play (Vstby/mute pin = 5V no signal)
50
60
60
100
110
110
200
180
180
µA
mA
mA
6/20
STA575
FUNCTIONAL DESCRIPTION
The circuit contains all the blocks to build a stereo amplifier. Each single channel is based on the Output Bridge
Power Amplifier, and its protection circuit. Moreover, the compression function and a signal rectifier are added
to complete the circuit.
The operation modes are driven by The Turn-on/off sequence block. In fact the IC can be set in three states by
the Stby/mute pin:
Standby ( Vpin < 0.8V), Mute (1.6V < Vpin < 2.5V), and Play (Vpin > 4V).
In the Standby mode all the circuits involved in the signal path are in off condition, instead
in Mute mode the circuits are biased but the Speakers Outputs are forced to ground potential.
These voltages can be get by the external RC network connected to Stby/Mute pin.
The same block is used to force quickly the I.C. In standby mode or in mute mode when the I.C. dangerous
condition has been detected. The RC network in these cases is used to delay the Normal operation restore.
The protection of the I.C. are implemented by the Over Temperature, Unbalance Ground, Output Short circuit,
Under voltage, and output transistor Power sensing as shown in the following table:
Table 1. Protection Implementation
Fault Type
Condition
Protection strategy
Action time
Release time
Chip Over
temperature
Tj > 130 °C
Mute
Fast
Slow Related to
Turn_on sequence
Chip Over
temperature
Tj > 150 °C
Standby
Fast
Slow, Related to
Turn_on sequence
Unbalancing
Ground
|Vgnd| > ((CD+) (CD-))/2 + 5V
Standby
Fast
Slow, Related to
Turn_on sequence
Short circuit
Iout > 7A
Standby
Fast
Slow, related to
Turn_on sequence
Under Voltage
|Vs+| + |Vs-|< 20V
Standby
Fast
Slow, related to
Turn_on sequence
Extra power
dissipation
at output transistor
Pd tr. > 32W
Reducing DIGITAL
CONVERTER output
voltage.
Related to the
DIGITAL
CONVERTER
Related to the
DIGITAL
CONVERTER
Maximum power
dissipation
at output transistor
Pd tr. > 60W
Standby
Fast
Slow, related to
Turn_on sequence
See the POWER PROTECTION paragraph for the details
Compression
An other important function implemented, to avoid high power dissipation and clipping distortion, is the Compression of the signal input. In fact the preamplifier stage performs a voltage gain equal to 5, fixed by Ri and Rr
external resistor, but in case of high input signal or low power supply voltage, its gain could be reduced of 26dB.
This function is obtained with a feedback type compressor that , in practice, reduces the impedance of the external feedback network. The behavior of compression it's internally fixed but depends from the Audio input voltage signal level, and from the Threshold voltage applied to the Threshold pin. The attack and release time are
programmable by the external RC network connected to the Att_Rel pins.
The constraints of the circuit in the typical application are the following:
Vthreshold range
= -5 to 0
Vin peak max
= 8V
Vout peak max
= 10V
7/20
STA575
Gain without compression (G)
=5
Max Attenuation ratio
= 26 dB
The following graph gives the representation of the Compressor activation status related to the Vthreshold and
the input voltage. The delimitation line between the two fields, compression or not, is expressed by the formula :
2 ⋅ ( Vth resho ld + 200 mV )
-------------------------------------------------------------------------G
Where G is the preamplifier gain without compression.
In the compression region the gain of the preamplifier will be reduced
(G = 2·Vthreshold/Vin) to maintain at steady state the output voltage equal 2*|Vthreshold| .
Instead in the other region the compressor will be off (G = 5).
The delimitation line between the two fields can be related to the output voltage of the preamplifier: in this case
the formula is :
V out = 2 ⋅ ( Vthre sho ld + 200mV )
Figure 1. Compressor activation field
VIN PEAK
8
6
COMPRESSION
G<5
4
2
G=5
D01AU1264
1
2
3
4
5
|Vthreshold|
The relative attenuation introduced by the variable gain cell is the following :
2 ( V th + 200 mV )
Atten uation = 20 log --- ⋅ -----------------------------------------V in_peak
5
The total gain of the stage will be:
Gdb = 20log5 + Attenuation
The maximum input swing is related to the value of input resistor, to guarantee that the input current remain
under Iin_Max value (1 mA).
V in_peak
R i > ---------------------I in_max
8/20
STA575
Figure 2. Compressor attenuation vs. input amplitude
Attenuation(dB)
0
-6
|Vth
-12
=5|
|Vth
-18
|Vt
=2.
5|
h=
1|
-24
D01AU1265
1
2
3
4
5
6
7
8
|Vinpk|
ABSOLUTE VALUE BLOCK
The absolute value block rectifies the signal after the compression to extract the control voltage for the external
digital converter. The output voltage swing is internally limited, the gain is internally fixed to 14.
The input impedance of the rectifier is very high , to allow the appropriate filtering of the audio signal before the
rectification (between Out_pre and Trk pins).
OUTPUT BRIDGE
The Output bridge amplifier makes the single-ended to Differential conversion of the Audio signal using two
power amplifiers, one in non-inverting configuration with gain equal to 2 and the other in inverting configuration
with unity gain. To guarantee the high input impedance at the input pins, Pwr_Inp1 and Pwr_Inp2, the second
amplifier stages are driven by the output of the first stages respectively.
POWER PROTECTION
To protect the output transistors of the power bridge a power detector is implemented (fig 3).
The current flowing in the power bridge and trough the series resistor Rsense is measured reading the voltage
drop between CD+1 and CD+. In the same time the voltage drop on the relevant power (Vds) is internally measured. These two voltages are converted in current and multiplied: the resulting current , Ipd, is proportional to
the instantaneous dissipated power on the relevant output transistor. The current Ipd is compared with the reference current Ipda, if bigger (dissipated power > 32W) a current, Iprot, is supplied to the Protection pin. The
aim of the current Iprot is to reduce the reference voltage for the digital converter supplying the power stage of
the chip, and than to reduce the dissipated power. The response time of the system must be less than 200µSec
to have an effective protection. As further protection, when Ipd reaches an higher threshold (when the dissipated
value is higher then 60W) the chip is shut down, forcing low the Stby/Mute pin, and the turn on sequence is
restarted.
9/20
STA575
Figure 3. Power Protection Block Diagram
RSENSE
CD+
CD+1
ILOAD
V/I
OC1
ILIM
MULTIPLIER
CURRENT COMP
X
PDP1
IPD
V/I
IPDP
I_PD
TO TURN-ON/OFF
SEQUENCE
CURRENT COMP
IPD
OPA
TO TURN-ON/OFF
SEQUENCE
IPROT
TO PROT PAD
OPA
IPDA
OUT1+
CD-
D01AU1266
OUT1-
In fig. 3 there is the power protection strategy pictures. Under the curve of the 32W power, the chip is in normal
operation, over 60W the chip is forced in Standby. This last status would be reached if the digital converter does
not respond quikly enough reducing the stress to less than 60W.
The fig.4 gives the protection current, Iprot, behavior. The current sourced by the pin Prot follows the formula:
–4
( Pd – Pd_av _th ) ⋅ 5 ⋅ 10
Iprot ≡ -----------------------------------------------------------------1.25V
for Pd < Pd_av_th the Iprot = 0
Independently of the output voltage, the chip is also shut down in the folowing conditions:
When the currentthrough the sensing resistor, R sense, reaches 7A (Voltage drop (CD+) - (CD+1) = 700mV).
When the average junction temperature of the chip reaches 150°C.
When the ground potential differ from more than 5V from the half of the power supply voltage, ((CD+)-(CD-))/2
When the sum of the supply voltage |Vs+| + |Vs-| <20V
The output bridge is muted when the average junction temperature reaches 130°C.
10/20
STA575
Figure 4. Power protection threshold
Figure 5. Protection current behaviour
Ids mA)
(
Iprot(mA)
Ilim = 6A
7
6
20
Standby
cK
Bu
4
Pd_M ax =48W
10
Li
mi
2
ta
Normal
ti
on
Operation
Iprot slope=0.4mA/W
Pd_reg = 25W
Vds (V
10
20
30
40
10
D01AU1268
50
20
30
40
50
Pd(W)
60
Figure 6. Test Circuit for STA575 Stand-alone
C5
C17
C7
R3
INPUT1
OUT_PRE1
R1
R7
R9
C1
TRK_1
9
8
R11
PWR_INP1
10
7
4
OUT1+
IN_PRE1
R5
ATT_REL1
5V
3
5
R16
CD+1
CD+
CD+
R17
R24
C12
C14
CD+2
+VS
+VS
C13
C15
-VS
-VS
CD-
CD-1
CD-2
TRK-OUT
TRK-OUT
PROT
R19
15
11
22
STBY/
MUTE
R14
C9
14
MUTE
STBY
R15
THRESH
13
24
OUT2+
C11
-VS
D1
R20
6
C10
GND
R22
R13
OUT1-
C3
PROT
THRESH
27
23
1
OUT2-
2
C4
26
16
25
ATT_REL2
12
17
R18
21
18
PWR_INP2
C2
19
TRK_2
R10
R12
R8
20
R6
IN_PRE2
INPUT2
R2
OUT_PRE2
C8
C6
R4
C16
D01AU1267
11/20
STA575
EXTERNAL COMPONENTS (refer to fig. 6)
Name
Function
Value
Formula
Ri
R1 = R2
Input resistor
10KΩ
(|G| = 5, Rr = 50KΩ)
Rr
R i = ------G
Rr
R3 = R4
Feedback resistor
50KΩ
(|G| = 5, Ri = 10KΩ
Rr = G ⋅ Rr
Cac
C1 = C2
AC Decoupling capacitor
100nF
(fp = 16Hz,
Rac =100KΩ )
1
Cac = --------------------------------2π ⋅ fp ⋅ Rac
Cct
C3 = C4
Capacitor for the attack time
2.2µF
(Tattack = 13mSec,
Vcontrol = 9V,
Ict = 1.5mA)
Ict
Cct = attack ------------------------Vcontrol
R5 = R6
Release constant time Resistor
470KΩ
(t = 1 Sec. ,
Cct = 2.2 µF )
τ
Rct = --------Cct
R7 = R8
Resistor for tracking input voltage
filter
10KΩ
R9 = R10
Resistor for tracking input voltage
filter
56KΩ
R11 = R12
Resistor for tracking input voltage
filter
10KΩ
C5 = C6
Capacitor for Tracking input
voltage filter
1nF
C7 = C8
Dc decoupling capacitor
1µF
R13
Bias Resistor for Stby/Mute
function
10KΩ
R14
Stby/Mute constant time resistor
30KΩ
R15
Mute resistor
30KΩ
C9
Capacitor for Stby/Mute resistor
2.2µF
R16 = R17
Sensing resistor for SOA detector
100mΩ
5% 4W
R18
Conversion resistor for threshold
voltage
100KΩ
C10 = C11
Power supply filter capacitor
100nF
R22 = R24
Centering resistor
C12 = C13
Tracking rail power supply filter
400 Ω , 1W
680nF
R19
Protection
1KΩ
R20
TRK_out
40KΩ
470 µF , 63V
C14 = C15
Power supply filter capacitor
C16 = C17
Feedback capacitor
100pF
Schottky diode
SB360
D1
Note: Vcontrol is the voltage at Att_Rel pin.
12/20
STA575
APPLICATION HINTS (refer to fig. 6)
PREAMPLIFIER AND COMPRESSOR
In the test circuit showed in figure 6, R1/R3 (or R2/R4) ratio fix the gain of the preamplifier.
If the input signal is very low, is possible to increase the gain fixing the product Vin∗G = cost.
In that case is possible to increase G decreasing R1,2 from 10KΩ until 2KΩ without relevant effetcs on the circuitbehavior and remaining in the operating range Iin_max = Vin_max/R1(2),<1mA.
So it is possible to increase the preamplifier gain until 25.
If no compression is present (equivalnt compressor Gm=0), the effects are:
– The output voltage offset increase
– The SNR decrease
The following table shows these variations:
R1,2
VIN MAX
G
VOFFSET
EN
10KΩ
8V
5
15mV
10µV
5KΩ
4V
10
30mV
13µV
2KΩ
1.6V
25
75mV
20µV
R3(4) = 50KΩ and all the other external components are the same
Attenuation = 0 dB
If the compression is active the circuit behaviour is the same.
It”s also possible to eliminate the compressor. In this case the ATT_REL (1,2) pin must be connected to gnd.
STBY-MUTE CIRCUIT
In the suggested application circuit (figure 6), the resistor for Standby/Mute function (R13) is connected between
the Standby/Mute switches and 5V Supply.
It is possible to connect the resistor to another Supply Voltage level VL, but in that case also the resistor value
(R13,14) must be changed according to the following formula (fixing VSTBY/MUTE = 2.5V and R15 = 10KΩ):
R 13 = ( 4 ⋅ VL – 10 )KΩ
R 14 = ( 4 ⋅ VL + 10 )KΩ
HEADROOM
In the suggested application circuit the supply voltage to obtain 75W (Power Output) on 8Ω (Rload)
is:
V supply = ∆V + I L, MAX ⋅ R DS on
It is also possible to increase the system’s efficiency forcing the headroom to follow the output signal (variable
drop insteadof a constant drop).
In that case:
V sup ply = ∆ V + IL ( V ) ⋅ RDS on
13/20
STA575
Figure 7. BASH® module SAM351 5.1 with 2 x STA575 (see application note AN1656)
Signal Power Supply
+/-24V DC / 50
mA
+50VDC
Dynamic Power Supply
(CD+ & CD-)
Buck
Regulator
STA575
2 x100Watts
Audio
Inputs
Lines
of
Controls
STABP01
Controller
STA575
2 x 100Watts
6 Ohm Loads
Audio
Input
STA575
2 x 100Watts
+/-24V DC / 50
mA
Signal Power Supply
Power - On-Off sequences:
In order to avoid damages to the SAM261 board it is important to follow these sequences:
At Power-On apply in the first the Auxiliary Power Supply (±24V) and after the Main Power Supply
(+50V), in this condition the system is in "Mute state" and it can move in "play state" with the switch present
on the pcb.
At Power-Off is better to bring the SAM module in "Mute state" and after that to follow this order: switchoff the Main Supply Voltage (+50V) and subsequently the Auxiliary Power Supply. (±24V).
System Description & Operating Rules
SAM351 is a BASH® 5.1 amplifier ( 6 x 100W) implementation utilizing the STA575 Integrated Circuit.
Specifically designed for multi-channel implementation in DVD - HTIB systems, Multi-Media systems, AV Receivers.
SAM351 is dimensioned to provide the maximum Output Power (THD=10 %) on two channels and instantaneously and 1/3 max Pout on the remaining Outputs, or 1/8 of max Pout continuous; this rule is important to
define the main Power Supply size (+50V).
Buck Regulator Description
The function of the buck regulator is to convert efficiently an input voltage to a lower voltage by adjusting the
ratio of the switching transistor's on-time to off-time. The resulting waveform is averaged by the output filter to
recover an analog signal.
In the BASH amplifier this output is in effect split in half by centering it on the audio ground to provide CD+ and
CD- rails.
To avoid the need for a high side driver for the transistor switch in the buck regulator the buck circuit recommended has the switch in the return path. Hence the gate drive circuit (part of the STPB01) is referenced to the
negative return of the main supply that provides power for the buck regulator.
14/20
STA575
Interfacing STA575 to STPB01 (Feedback circuit)
This circuit produces a control signal current that is fed back to the STPB01 digital controller. The network used
in this example compares the track signal (STA575 track out) to a fixed ratio of buck regulator's output (CD+)
using a transistor. This method is effective because the controller's reference is the negative of the main DC
supply, which is not referenced to audio ground.
The tracking signal is generated inside the STA575 (track out) by taking the absolute value of the pre-amp's
output. The outputs of each channel and of each STA575 are then tied together in a diode-oring arrangement.
This means that the highest of any given output is the output that determines the tracking signal.
The absolute value circuit inside the STA575 has gain. This makes it possible to use an RC network and a resistor divider to create a phase shift in the tracking signal at higher frequencies. This is also useful in optimizing
the alignment of the buck regulator's output with the output signal of the bridge amplifier at high frequency
This circuit first converts the buck switch current to a peak voltage. The control current is then converted to a
voltage (using a resistor) and added to the peak voltage. By doing this, the buck is better able to maintain the
desired headroom over a wide load range and output level.
Centering Network for CD+ & CD- Rails
The power rail of a bridge amplifier has no current flowing through the ground node, as the load is not connected
to ground. However there are several different small sources of dynamic and continuos ground currents flowing
from either CD+ or CD- to support the function of various things such as the control signal to the STABP01 controller.
The centering network prevents these currents from shifting the CD+/- rails away from center i.e. away from a
symmetric split of the buck's output about ground. This is critical, even a small centering error requires an increase in headroom which results in a significant drop in output losses. In its simplest form the centering network
could be a resistor divider from CD+ to CD- with its center tied to ground.
As long as the impedance is low enough (for example 200 ohms) this will swamp the smaller offset currents. It
is helpful to put this kind of passive network on the board with the STA575 devices to help when testing this
board on its own.
Power Amplifier Heatsink requirements
The heatsink requirements are dependent on several design goals. However there are two common references:
Pink noise at 1/8 of full power, all channels loaded. This would approximate a system with all channels reproducing music at full volume with clipping occurring only occasionally. The second would be full power at 1kHz
for 5 minutes after a one hour pre-soak at 1/8 power.
The worse of these two is the full power test. A conservative approach is to assume that the heatsink would
come to thermal equilibrium after 5 minutes. Thus the Rth of the heatsink can be determined by:
T jmax – T amb
R th heatsink = ---------------------------------- – R th –j
Pd
ca se
– R th
c as e to heatsink
For example in the STA575 the Rth jc is 1°C / W. R case-to-heatsink with grease is about 0.5°C / W. The maximum operating junction temperature is 130°C, which for margin should be derated to 120°C
Buck Regulator Heatsink
The Buck regulator heatsink can be designed in a similar manner and does not change by varying power supply.
In general the efficiency will be in the order of 85%. The thermal impedances from the junction(s) to the heatsink
may be lower and the maximum operating temperature will be higher.
Usually either the sub or the remaining channels are tested at full power. The result is that usually the Buck
heatsink is about ¼ the size of the linear heatsink, but this can be strongly affected by the design.
15/20
STA575
Figure 8. PCBs AND COMPONENTS LAYOUT
4 Pin Harness
Power Supply Connections
50 VDC
Input
+/-24 VDC
Input
Mute
Channel 1 and 2
Channel 3 and 4
Channel 5
Channel 6
9 Pin Harness
Audio Connections
SAM261 Specification
Parameter
Rating
Notes
Output Power
100Watts @10% - 6Ω
see graphs
THD + N
< 0.05% @ 40 Watts
< 0.05% @ 75 Watts
Measured @ 1KHZ
SNR
-104 dB (relative to full power)
-113 dB (A-weighted)
Sensitivity
1 .3VRMS
Amplifier
Crosstalk
-76dB (relative to10W)
1KHz 8 Ohms,
Main Power Supply Inputs
60Volts @ 4 Amps
Maximum Voltage is 60V
Minimum Voltage is 50V
Aux Power Supply Inputs
+ 24 Volts @ 100mA
-24 Volts @ 100mA
Vs supply
Input Board
1 .3VRMS
Suplied to facilitate testing
16/20
STA575
Figure 9. THD +N FR Channel
Figure 11. Residual Noise vs. Frequency
Audio Precision
Audio Precision
10
+0
5
-20
2
-40
1
-60
0.5
dBr
-80
%
0.2
-100
0.1
-120
0.05
-140
0.02
-160
0.01
10
20
30
40
50
60
70
80
90
100
110
120
130
140
20
50
100
200
W
Figure 10. THD + N Frequency
2k
5k
10k
20k
Audio Precision
10
5
2
1
0.5
Pout = 30W
%
0.2
Pout = 80W
0.05
0.02
0.01
20
1k
Figure 12. Frequency Response
Audio Precision
0.1
500
Hz
Pout = 5W
50
100
200
500
Hz
1k
2k
5k
10k
20k
+40
+38
+36
+34
+32
+30
+28
+26
+24
+22
dBr +20
+18
+16
+14
+12
+10
+8
+6
+4
+2
+0
10
20
50
100
200
500
Hz
1k
2k
5k
10k
20k
40k
17/20
STA575
Figure 13. APPICATION BLOCK DIAGRAM
+VS
-VS
+VS
MUTE
-VS
MUTE
MUTE
MUTE CONTROL &
THRESHOLD
REFERENCE
STA575
2 CHANNELS
MUTE
THRESH-REF
THRESH-REF
OUT1+
IN1
MUTE-BUCK
OUT1-
RED
+VS
+VS
-VS
-VS
TRACK
J1
BUCK CONTROLLER
I-SENSE
OUT2-
WHITE
PROT
DC++
GATE-DRIVE
OUT2+
IN2
MUTE-BUCK
CD-
TRACK
CD+
PROT
CD+
STA575
CD+
PWM-SPLY
DC++
GND
L2
I-SENSE
GATE-DRIVE
J2
CD-
PWM-SPLY
1800pF
J1
CD+
CD-
CD-
MUTE
2 CHANNELS
TRACK
OUT3+
IN3
300W BUCK
OUT3-
RED
DC++
15µH
J2
-VS
+VS
J3
OUT4+
IN4
1800pF
PROT
OUT4-
WHITE
J4
-VS
+VS
CD+
STA575
CD-
2 CHANNELS
MUTE-LIN
PROT
TRACK
-VS
+VS
J3
RED
IN5
OUT5+
OUT0-
J5
R77
IN6
J4
D02AU1454
18/20
R78
OUT6+
OUT8-
J6
STA575
DIM.
MIN.
4.45
1.80
A
B
C
D
E
F (1)
G
G1
H (2)
H1
H2
H3
L (2)
L1
L2 (2)
L3
L4
L5
M
M1
N
O
R
R1
R2
R3
R4
V
V1
V2
V3
0.75
0.37
0.80
25.75
28.90
22.07
18.57
15.50
7.70
3.70
3.60
mm
TYP.
4.50
1.90
1.40
0.90
0.39
1.00
26.00
29.23
17.00
12.80
0.80
22.47
18.97
15.70
7.85
5
3.5
4.00
4.00
2.20
2
1.70
0.5
0.3
1.25
0.50
MAX.
4.65
2.00
MIN.
0.175
0.070
1.05
0.42
0.57
1.20
26.25
29.30
0.029
0.014
22.87
19.37
15.90
7.95
0.869
0.731
0.610
0.303
4.30
4.40
0.145
0.142
0.031
1.014
1.139
inch
TYP.
0.177
0.074
0.055
0.035
0.015
0.040
1.023
1.150
0.669
0.503
0.031
0.884
0.747
0.618
0.309
0.197
0.138
0.157
0.157
0.086
0.079
0.067
0.02
0.12
0.049
0.019
MAX.
0.183
0.079
OUTLINE AND
MECHANICAL DATA
0.041
0.016
0.022
0.047
1.033
1.153
0.904
0.762
0.626
0.313
0.169
0.173
5˚ (Typ.)
3˚ (Typ.)
20˚ (Typ.)
45˚ (Typ.)
Flexiwatt27 (vertical)
(1): dam-bar protusion not included
(2): molding protusion included
V
C
B
V
H
H1
V3
A
H2
O
H3
R3
L4
R4
V1
R2
L2
N
L3
R
L
L1
V1
V2
R2
D
R1
L5
Pin 1
R1
R1
E
G
G1
F
FLEX27ME
M
M1
7139011
19/20
STA575
Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences
of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted
by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject
to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not
authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics.
The ST logo is a registered trademark of STMicroelectronics
2003 STMicroelectronics - All Rights Reserved
is the registered trademark and patented technology of INDIGO manufacturing inc.
STMicroelectronics GROUP OF COMPANIES
Australia - Brazil - Canada - China - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan -Malaysia - Malta - Morocco Singapore - Spain - Sweden - Switzerland - United Kingdom - United States.
http://www.st.com
20/20
AN1656
APPLICATION NOTE
6 CH VOLUME CONTROLLER
PLUS SAM351 BASH AMPLIFIER
by Luigi Pagotto & Marco Motta
In this document is explained how to connect the Audio processor TDA7448 to the board BASH
SAM351, in order to obtain a complete amplifier with the volume controlled via I2C bus.
Before to start the description we summarize what are the characteristic of the two boards.
TDA7448 Board:
With this board is possible to obtain the independent Volume Control for six channels in 1.0dB Steps, the
Volume attenuation ranges from 0 to -79dB.
All functions are programmable via serial Bus (I2C).
The board is feed with a supply voltage ranging from 4.75 to10V.
It will be also described how to use the control sw.
SAM351 BOARD:
SAM351 is a [email protected] (6x100W) amplifier utilizing the STA575 IC.
This board is specifically designed for multi-channel implementation in DVD - HTIB
Systems, Multi - Media systems, AV Receivers.
SAM351 is dimensioned to provide the maximum Output Power (@ THD= 10%) on two channels and 1/
3 max Pout on the remaining Outputs, this assumption is important to define the main Power Supply size
(+50V).
In this document we describe an application configuration where the used loads are:
6 x 100W @ 6 ohm
CONTROL SOFTWARE
Figure 1.
February 2003
1/6
AN1656 APPLICATION NOTE
Once installed, the control software will appear as shown in fig.1, here below is explained how to work with
it.
STEP 1:
Clicking on the "parallel port" icon it will appear the following image.
Figure 2.
The program automatically detects the printer ports installed in the system and enables them. Select the
port connected to the device evaluation board through the appropriate interface. To verify if the device is
working, press the button with the binocular.
The program scans all possible device address and stops when it receives the acknowledge. To restore
default device address press the button with the default value.
The clock frequency slider allows the user to vary the communication speed.
Three buttons set the bus operating mode:
– ACK detection. It toggles ACK detection ON/OFF. If the ack detection is ON and the device is not
acknowledging the commands, the button is RED, signaling that ack error occurred on last command.
Incremental mode. It toggles incremental bus ON/OFF .When incremental bus is active all the preset commands are sent by using incremental bus mode (i.e. the message is made by the first subaddress and then all the data bytes follow. The device automatically increments the destination address internally). The Send button acts as well
– Block mode. It toggles block mode ON/OFF . When block mode is ON , any variation in Volume is
not sent to the device in real time. Commands are sent all together either when user click on Send
command or block mode is turned to OFF.
STEP 2:
Push the Button 0 in order to Load the default reset condition.
It is possible now to Increment /Decrement the Volume attenuation acting on the Sliders
command or pushing the buttons that allow to attenuate by one step.
It is possible to save 4 settings for the Volume pressing the Buttons [1…4] + SHIFT.
2/6
AN1656 APPLICATION NOTE
Additional Features:
Acting on the button
is shown the registers' table, where is shown the current value of all the device's registers. It is real time updated as the user modifies any parameter. It is possible to entry directly
a value in binary, hexadecimal or decimal notation by clicking on the correspondent cell and inserting a
new value.
The send command
refresh all registers of the device with current settings.
It may use the incremental mode it is enabled.
PCB and Components Layout
In fig.2 is shown how to connect the two boards TDA7448 and SAM351 in order to have a complete amplification system with Volume control via I2C.
To complete the application it is necessary to provide the correct Power Supply for the two boards as follows:
TDA7448: (connector J6)
The supply voltage to be used can range from +5 up to +10V
SAM351: (connector J9)
SAM351 module utilize two supply voltages:
– Signal Supply Voltage +/-Vs: +/- 24Vdc / 100mA
– Power Section Voltage +/-DC: +50V /4.0A
In the dimensioning of the power section is important to know that the module is able to provide the maximum power (@THD=10%) on two channels and instantaneously 1/3 Max Pout on the remaining outputs
or continuously 1/8 of Max. Pout.
The two supply voltages are completely separated between them: the signal VS is splitted (+/-24V) and
its central point (A-gnd) is the reference ground for the STA575 circuits (inputs, stand-by, etc.), while the
Power DC is a single supply and its reference must be completely isolated from A-gnd.
In order to implement the Mute function for the SAM351 module it is necessary to connect a wire to the
pin.9 of the connector J8:
– when pin.9 open: SAM351 module is Muted
– when pin.9 is at 15V: SAM351 module is in Play.
All the 6 channels are configurated in BTL and completely separated among them and isolated from the
rest of the system.
3/6
J9
4DC3DC+
2VS1VS+
Audio
nput
signals
I2C Bus
Connector Description
9
J4
8
Gnd
7
Out6
Out5
Out4
Out3
Out2
Out1
Power Supply
Connector
Speakers connectors
J8
NC
6
5
4
3
2
1
50v
+15V Play
OpenMute
GND to Supply
-24v
+24v
AN1656 APPLICATION NOTE
Connector
Audio
Signals
– Interfacing TDA7448 to BASH@SAM351
Figure 3.
4/6
Vcc
AN1656 APPLICATION NOTE
BASH@SAM351 module 6.1 configuration:
Figure 4. Block Diagram
STA575
2 x 100Watts
Audio Inputs
STABP01
Converter
60VDC
6 Ohm Loads
STA575
2 x 100Watts
+/- 24VDC 50mA
For each STA530
Audio Inputs
STA575
2 x 100Watts
Audio Inputs
System Specification
Table 1.
Parameter
Rating
Notes
Output Power
Sats @6ohm – 100W@THD10%
See Graphs
THD+N
<0.05% @ 40W
<0.05% @ 75W
Measured
@ 1KHz
SNR
-104dB (relative to full power)
-113dB (A-weighted)
Sensitivity
1.3VRMS
Amplifier
Crosstalk
-76dB (relative to 10W)
1KHz, 8 ohms
Main Power Supply
60V / 4A
Max Voltage is 60V
Min. Voltage is 50V
Aux Power Supply
+/- 24V / 100mA
Vs supply
Input Board
Supplied to facilitate
5/6
AN1656 APPLICATION NOTE
Power - Up sequences:
In order to avoid damages to the SAM351 board it is important to follow these sequences:
At Power-On apply in the first the Auxiliary Power Supply (±24V) and after the Main Power Supply
(+50V), in this condition the system is in "Mute state" and it can move in "play state" with the switch present
on the pcb.
At Power-Off is better to bring the SAM module in "Mute state" and after that to follow this order: switchoff the Main Supply Voltage (+50V) and subsequently the Auxiliary Power Supply. (±24V).
Figure 5. Thd +noise vs. Output Power
10
5
2
1
0.5
%
0.2
0.1
0.05
0.02
0.01
0
10
20
30
40
50
60
70
80
90
100
110
W
Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences
of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted
by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject
to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not
authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics.
The ST logo is a registered trademark of STMicroelectronics
© 2003 STMicroelectronics - All Rights Reserved
STMicroelectronics GROUP OF COMPANIES
Australia - Brazil - Canada - China - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan -Malaysia - Malta - Morocco Singapore - Spain - Sweden - Switzerland - United Kingdom - United States.
http://www.st.com
6/6