收藏本站
LTC6990
19
6990fc
For more information www.linear.com/LTC6990
Figure 14. Digitally Controlled Oscillator with VSET Variation Eliminated
6990 F14
LTC6990
OE
GND
SET
OUT
V+
DIV
C1
0.1F
R1
R2
RSET
V+
RVCO
–
+
V+
1/2
LTC6078
LTC1659
V+
VCC
REF
GND
VOUT
P
DIN
CLK
CS/LD
fOUT =
1MHz 50k
NDIV RVCO
1
+
RVCO
RSET
DIN
4096
DIN = 0 to 4095
Additionally, by choosing the VCO’s specifications
shrewdly, the frequency error (in percent) due to VSET
variation is reduced to VSET/VSET = ±3%. To realize this
improvement, the design must abide by three conditions.
First, the VIN voltage must be positive throughout the
range. Second, choose VMAX/VMIN ≥ fMAX/fMIN. Last,
choose RVCO/RSET ≥ R4/R3.
Figure 13 shows a design similar to the previous design
example where the VMIN voltage is now specified to be
0.4V. This satisfies the VMAX/VMIN ≥ fMAX/fMIN condition
and the design assures that the output frequency error
due to VSET variation is only ±3%.
Eliminating VSET Error Effects with DAC Frequency
Control
Many DACs allow for the use of an external reference.
If such a DAC is used to provide the VCTRL voltage, the
VSET error is eliminated by buffering VSET and using it as
the DAC’s reference voltage, as shown in Figure 14. The
DAC’s output voltage now tracks any VSET variation and
eliminates it as an error source. The SET pin cannot be
tied directly to the reference input of the DAC because
the current drawn by the DAC’s REF input would affect
the frequency.
APPLICATIONS INFORMATION
ISET Extremes (Master Oscillator Frequency Extremes)
Pushing ISEToutsideoftherecommended1.25Ato20A
range forces the master oscillator to operate outside of the
62.5kHz to 1MHz range in which it is most accurate. The
oscillator will still function with reduced accuracy in its
extendedrange(seetheElectricalCharacteristicssection).
The LTC6990 is designed to function normally for ISET
as low as 1.25A. At approximately 500nA, the oscillator
output will be frozen in its current state. For NDIV = 1 or 2,
OUT will halt in a low state. But for larger divider ratios,
it could halt in a high or low state. This avoids introduc-
ing short pulses while modulating a very low frequency
output. Note that the output will not be
disabled as when
OE is low (e.g. the output will not enter a high impedance
state if Hi-Z = 1).
At the other extreme, the master oscillator frequency can
reach 2MHz for ISET = 40μA (RSET = 25k). It is not recom-
mended to operate the master oscillator beyond 2MHz
because the accuracy of the DIV pin ADC will suffer.
发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

*型号 *数量 厂商 批号 封装
添加更多采购

我的联系方式

*
*
*
相关PDF资料
LTC6991MPS6#TRPBF IC OSCILLATOR RESET LF TSOT23-6
LTC6992MPS6-4#TRPBF IC OSC PWM VOLT CTLR TSOT23-6
LTC6994CDCB-2#TRPBF IC DELAY LINE 6-DFN
LTC7541ABN#PBF IC CMOS D/A CONV 12BIT 18-DIP
LTC7545ACG#TRPBF IC D/ACONV MULTIPLY 12BIT 20SSOP
LTC8043EN8 IC D/A CONV 12BIT SERIAL 8-DIP
LTC8143ESW#TRPBF IC D/A CONV 12BIT SERIAL 16-SOIC
LTM9011CY-14#PBF IC ADC 14BIT UMODULE 140BGA
相关代理商/技术参数
LTC6991 制造商:LINER 制造商全称:Linear Technology 功能描述:TimerBlox: Resettable, Low Frequency Oscillator
LTC6991CDCB#TRMPBF 功能描述:IC OSC SILICON 977HZ 6-DFN RoHS:是 类别:集成电路 (IC) >> 时钟/计时 - 可编程计时器和振荡器 系列:TimerBlox® 标准包装:3,000 系列:- 类型:振荡器 - 晶体 计数:- 频率:- 电源电压:2.3 V ~ 5.5 V 电流 - 电源:1.07mA 工作温度:-30°C ~ 80°C 封装/外壳:SOT-665 包装:带卷 (TR) 供应商设备封装:SS迷你型-5D 安装类型:表面贴装 其它名称:AN8955SSMTXLTR
LTC6991CDCB#TRPBF 功能描述:IC OSC SILICON 977HZ 6-DFN RoHS:是 类别:集成电路 (IC) >> 时钟/计时 - 可编程计时器和振荡器 系列:TimerBlox® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:45 系列:- 类型:温度 - 补偿晶体振荡器（TCXO） 计数:- 频率:25MHz 电源电压:3.135 V ~ 3.465 V 电流 - 电源:1.5mA 工作温度:-40°C ~ 85°C 封装/外壳:16-SOIC（0.295"，7.50mm 宽） 包装:管件 供应商设备封装:16-SOIC W 安装类型:表面贴装
LTC6991CDCBPBF 制造商:LINER 制造商全称:Linear Technology 功能描述:TimerBlox: Resettable, Low Frequency Oscillator
LTC6991CS6#PBF 制造商:Linear Technology 功能描述:OSCILLATOR 977HZ 5.5V TSOT-23-6 制造商:Linear Technology 功能描述:OSCILLATOR, 977HZ, 5.5V, TSOT-23-6, Operating Mode:-, No. of Timers:1, Frequency 制造商:Linear Technology 功能描述:OSCILLATOR, 977HZ, 5.5V, TSOT-23-6, Operating Mode:(Not Available), No. of Timers:1, Frequency:977Hz, Supply Voltage Min:2.25V, Supply Voltage Max:5.5V, Digital IC Case Style:TSOT-23, No. of Pins:6, Operating Temperature Min:0C , RoHS Compliant: Yes
LTC6991CS6#TRMPBF 功能描述:IC OSC SILICON 977HZ TSOT23-6 RoHS:是 类别:集成电路 (IC) >> 时钟/计时 - 可编程计时器和振荡器 系列:TimerBlox® 标准包装:3,000 系列:- 类型:振荡器 - 晶体 计数:- 频率:- 电源电压:2.3 V ~ 5.5 V 电流 - 电源:1.07mA 工作温度:-30°C ~ 80°C 封装/外壳:SOT-665 包装:带卷 (TR) 供应商设备封装:SS迷你型-5D 安装类型:表面贴装 其它名称:AN8955SSMTXLTR
LTC6991CS6#TRPBF 功能描述:IC OSC SILICON 977HZ TSOT23-6 RoHS:是 类别:集成电路 (IC) >> 时钟/计时 - 可编程计时器和振荡器 系列:TimerBlox® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:45 系列:- 类型:温度 - 补偿晶体振荡器（TCXO） 计数:- 频率:25MHz 电源电压:3.135 V ~ 3.465 V 电流 - 电源:1.5mA 工作温度:-40°C ~ 85°C 封装/外壳:16-SOIC（0.295"，7.50mm 宽） 包装:管件 供应商设备封装:16-SOIC W 安装类型:表面贴装
LTC6991CS6PBF 制造商:LINER 制造商全称:Linear Technology 功能描述:TimerBlox: Resettable, Low Frequency Oscillator