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參數資料
| 型號： | MAX9814EVKIT+ |
| 廠商： | Maxim Integrated Products |
| 文件頁數： | 13/14頁 |
| 文件大小： | 0K |
| 描述： | EVALUATION KIT FOR MAX9814 |
| 產品培訓模塊： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 標準包裝： | 1 |
| 放大器類型： | AB 類 |
| 輸出類型： | 1-通道（單聲道） |
| 電源電壓： | 2.7V ~ 5.5V |
| 工作溫度： | -40°C ~ 85°C |
| 板類型： | 完全填充 |
| 已用 IC / 零件： | MAX9814 |
| 已供物品： | 板 |
Attack Time
The attack time is the time it takes for the AGC to
reduce the gain after the input signal has exceeded the
threshold level. The gain attenuation during the attack
time is exponential, and defined as one-time constant.
The time constant of the attack is given by 2400 x CCT
seconds (where CCT is the external timing capacitor):
Use a short attack time for the AGC to react quickly
to transient signals, such as snare drum beats
(music) or gun shots (DVD).
Use a longer attack time to allow the AGC to ignore
short-duration peaks and only reduce the gain when
a noticeable increase in loudness occurs. Short-
duration peaks are not reduced, but louder pas-
sages are. This allows the louder passages to be
reduced in volume, thereby maximizing output
dynamic range.
Hold Time
Hold time is the delay after the signal falls below the
threshold level before the release phase is initiated.
Hold time is internally set to 30ms and nonadjustable.
The hold time is cancelled by any signal exceeding the
set threshold level, and the attack time is reinitiated.
Release Time
The release time is how long it takes for the gain to
return to its normal level after the output signal has fall-
en below the threshold level and 30ms hold time has
expired. Release time is defined as release from a
20dB gain compression to 10% of the nominal gain set-
ting after the input signal has fallen below the TH
threshold and the 30ms hold time has expired. Release
time is adjustable and has a minimum of 25ms. The
release time is set by picking an attack time using CCT
and setting the attack-to-release time ratio by configur-
ing A/R as shown in Table 1:
Use a small ratio to maximize the speed of the AGC.
Use a large ratio to maximize the sound quality and
prevent repeated excursions above the threshold
from being independently adjusted by the AGC.
AGC Output Threshold
The output threshold that activates AGC is adjustable
through the use of an external resistive divider. Once
the divider is set, AGC reduces the gain to match the
output voltage to the voltage set at the TH input.
Microphone Bias
The MAX9814 features an internal low-noise micro-
phone bias voltage capable of driving most electret
condenser microphones. The microphone bias is regu-
lated at 2V to provide that the input signal to the low-
noise preamplifier does not clip to ground.
Applications Information
Programming Attack and Release Times
Attack and release times are set by selecting the
capacitance value between CT and GND, and by set-
ting the logic state of A/R (Table 1). A/R is a tri-level
logic input that sets the attack-to-release time ratio.
The attack and release times can be selected by utiliz-
ing the corresponding capacitances listed in Table 2.
Microphone Amplifier with AGC and
Low-Noise Microphone Bias
10ms/div
VCT
500mV/div
VMICOUT
(AC-COUPLED)
1V/div
ATTACK
RELEASE
HOLD
0V
A/R
ATTACK/RELEASE RATIO
GND
1:500
VDD
1:2000
Unconnected
1:4000
Figure 2. Input Burst Exceeding AGC Limit
Table 1. Attack-and-Release Ratios
tRELEASE (ms)
CCT
tATTACK
(ms)
A/R =
GND
A/R =
VDD
A/R =
UNCONNECTED
22nF
0.05
25
100
200
47nF
0.11
55
220
440
68nF
0.16
80
320
640
100nF
0.24
120
480
960
220nF
0.53
265
1060
2120
470nF
1.1
550
2200
4400
680nF
1.63
815
3260
6520
1F
2.4
1200
4800
9600
Table 2. Attack-and-Release Time
MAX9814
8
Maxim Integrated
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| MAX9814EVKIT+ | 功能描述:音頻 IC 開發工具 MAX9814 Eval Kit RoHS:否 制造商:Texas Instruments 產品:Evaluation Kits 類型:Audio Amplifiers 工具用于評估:TAS5614L 工作電源電壓:12 V to 38 V |
| MAX981CPA | 功能描述:校驗器 IC Single Comparator / Reference RoHS:否 制造商:STMicroelectronics 產品: 比較器類型: 通道數量: 輸出類型:Push-Pull 電源電壓-最大:5.5 V 電源電壓-最小:1.1 V 補償電壓（最大值）:6 mV 電源電流（最大值）:1350 nA 響應時間: 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:SC-70-5 封裝:Reel |
| MAX981CPA+ | 功能描述:校驗器 IC Single Comparator / Reference RoHS:否 制造商:STMicroelectronics 產品: 比較器類型: 通道數量: 輸出類型:Push-Pull 電源電壓-最大:5.5 V 電源電壓-最小:1.1 V 補償電壓（最大值）:6 mV 電源電流（最大值）:1350 nA 響應時間: 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:SC-70-5 封裝:Reel |
| MAX981CSA | 功能描述:校驗器 IC RoHS:否 制造商:STMicroelectronics 產品: 比較器類型: 通道數量: 輸出類型:Push-Pull 電源電壓-最大:5.5 V 電源電壓-最小:1.1 V 補償電壓（最大值）:6 mV 電源電流（最大值）:1350 nA 響應時間: 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:SC-70-5 封裝:Reel |
| MAX981CSA+ | 功能描述:校驗器 IC Single Comparator / Reference RoHS:否 制造商:STMicroelectronics 產品: 比較器類型: 通道數量: 輸出類型:Push-Pull 電源電壓-最大:5.5 V 電源電壓-最小:1.1 V 補償電壓（最大值）:6 mV 電源電流（最大值）:1350 nA 響應時間: 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:SC-70-5 封裝:Reel |
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