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| 型号： | MAX1499ECJ+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 21/33页 |
| 文件大小： | 0K |
| 描述： | IC ADC 3 1/2DIG W/LED DVR 32TQFP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,000 |
| 位数： | 3.5 位 |
| 采样率（每秒）： | 5 |
| 数据接口： | MICROWIRE?，QSPI?，串行，SPI? |
| 转换器数目： | 1 |
| 电压电源： | 模拟和数字 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 32-LQFP |
| 供应商设备封装： | 32-LQFP（7x7） |
| 包装： | 带卷 (TR) |
| 输入数目和类型： | 1 个差分，双极 |
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MAX1497/MAX1499
3.5- and 4.5-Digit, Single-Chip ADCs with LED
Drivers and C Interface
28
______________________________________________________________________________________
Choosing Supply Voltage to Minimize
Power Dissipation
The MAX1497/MAX1499 drive a peak current of
25.5mA into LEDs with a 2.2V forward-voltage drop
when operated from a supply voltage of at least 3.0V.
Therefore, the minimum voltage drop across the inter-
nal LED drivers is (3.0V - 2.2V) = 0.8V. The MAX1497/
MAX1499 sink (8 x 25.5mA = 204mA) when the outputs
are operating and LED segment drivers are at full cur-
rent. For a 3.3V supply, the MAX1497/MAX1499 dissi-
pate (3.3V - 2.2V) x 204 = 224.4mW. If a higher supply
voltage is used, the driver absorbs a higher voltage,
and the driver’s power dissipation increases according-
ly. However, if the LEDs used have a higher forward
voltage drop than 2.2V, the supply voltage must be
raised accordingly to ensure that the driver always has
at least 0.8V headroom.
For a VLED supply voltage of 2.7V, the maximum LED
forward voltage is 1.9V to ensure 0.8V driver headroom.
The voltage drop across the drivers with a nominal +5V
supply (5.0V - 2.2V = 2.8V) is almost three times the
drop across the drivers with a nominal 3.3V supply
(3.3V - 2.2V = 1.1V). Therefore, the driver’s power dissi-
pation increases three times. The power dissipation in
the part causes the junction temperature to rise accord-
ingly. In the high ambient temperature case, the total
junction temperature may be very high (>+125°C). At
higher junction temperatures, the ADC performance
degrades. To ensure the dissipation limit for the
MAX1497/MAX1499 is not exceeded and the ADC per-
formance is not degraded, a diode can be inserted
between the power supply and VLED.
Computing Power Dissipation
The following can be used to compute power dissipa-
tion:
PD = (VLED x IVLED ) + (VLED - VDIODE)
(DUTY x ISEG x N) + VSUPPLY x ISUPPLY
VLED = LED driver supply voltage
IVLED = VLED bias current
VDIODE = LED forward voltage
DUTY = segment ON time during each digit ON time
ISEG = segment current set by RISET
N = number of segments driven (worst case is eight)
VSUPPLY = supply voltage of the part
ISUPPLY = supply current from VDD for the MAX1497 or
AVDD + DVDD for the MAX1499
Dissipation Example
For ISEG = 25.5mA, N = 8, DUTY = 127 / 128, VDIODE =
1.5V at 25.5mA, VLED = VSUPPLY = 5.25V:
PD = (5.25 x 2mA) + (5.25V - 1.5) [(127 / 128)
x 25.5mA x 8)] + 5.25 x 1.080mA
PD = 0.7751W
28-Pin SSOP Package Example
For the 28-pin SSOP package (TJA = 1 / 0.009496 =
+105.3°C/W), the maximum allowed ambient tempera-
ture TA is given by:
TJ (max) = TA + (PD x TJA) =
+125°C = TA + (0.7751W x +105.3°C/W)
TA = +43°C
Thus, the device cannot operate safely at a maximum
package temperature of +85°C. The power dissipates
in the part need to be lowered.
(PD x TJA) max = (+125°C) - (+85°C) = +40°C
PD (max) = +40°C /+105.3°C/W = 380mW
(VLED - VDIODE) = [380mW - (5.25V x 2mA) - 5.25V x
1.080mA] / [(127 / 128) x 25.5mA x 8]
VLED - VDIODE = 1.854V
VLED - VDIODE should have the following condition to
ensure it operates safely:
0.8V < VLED - VDIODE < 2.08V
28-Pin PDIP Package Example
PD x TJA (max) = (+125°C) - (+85°C) = +40°C
PD (max) = +40°C /+70°C/W = 571mW
VLED - VDIODE = [571mW - (5.25V x 2mA) - 5.25V x
1.080mA] / [(127 / 128) x 25.5mA x 8]
VLED - VDIODE = 2.80V
For a 28-pin PDIP package, VLED - VDIODE should
have the following condition to ensure it operates safe-
ly:
0.8V < VLED - VDIODE < 3.18V
32-Pin TQFP Package
The MAX1499 TQFP package can operate safely for all
supply voltages provided VDIODE > 1.5V.
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| MAX1499EVC16 | 功能描述:模数转换器 - ADC 3.5- and 4.5-Digit Single-Chip ADCs with LED Drivers and uC Interface RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| MAX1499EVKIT | 功能描述:数据转换 IC 开发工具 Evaluation Kit/Evaluation System for the MAX1499 RoHS:否 制造商:Texas Instruments 产品:Demonstration Kits 类型:ADC 工具用于评估:ADS130E08 接口类型:SPI 工作电源电压:- 6 V to + 6 V |
| MAX149ACAP | 功能描述:模数转换器 - ADC Integrated Circuits (ICs) RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| MAX149ACAP+ | 功能描述:模数转换器 - ADC 10-Bit 8Ch 133ksps 5.25V Precision ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| MAX149ACAP+T | 功能描述:模数转换器 - ADC 10-Bit 8Ch 133ksps 5.25V Precision ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
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