- 您现在的位置：买卖IC网 > PDF目录1774 > A8293SETTR-T (Allegro Microsystems Inc)IC REG LNB BOOST/LINEAR 28QFN PDF资料下载
参数资料
| 型号： | A8293SETTR-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 6/19页 |
| 文件大小： | 0K |
| 描述： | IC REG LNB BOOST/LINEAR 28QFN |
| 标准包装： | 9,000 |
| 应用： | 转换器，模拟和数字式卫星信号 STB 接收器/SatTV |
| 输入电压： | 9 V ~ 16 V |
| 输出数： | 1 |
| 输出电压： | 可调 |
| 工作温度： | -20°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-VFQFN |
| 供应商设备封装： | 28-QFN |
| 包装： | 带卷 (TR) |
A8293
Single LNB Supply and Control Voltage Regulator
Functional Description
Protection
The A8293 has a wide range of protection features and fault diag-
nostics which are detailed in the Status Register section.
Boost Converter/Linear Regulator
The A8293 solution contains a tracking current-mode boost
converter and linear regulator. The boost converter tracks the
requested LNB voltage to within 800 mV, to minimize power
dissipation. Under conditions where the input voltage, V BOOST ,
is greater than the output voltage, V LNB , the linear regulator must
drop the differential voltage. When operating in these conditions,
care must be taken to ensure that the safe operating temperature
range of the A8293 is not exceeded.
The boost converter operates at 352 kHz typical: 16 times
the internal 22 kHz tone frequency. All the loop compensation,
current sensing, and slope compensation functions are provided
internally.
The A8293 has internal pulse-by-pulse current limiting on
the boost converter and DC current limiting on the LNB output
to protect the IC against short circuits. When the LNB output is
shorted, the LNB output current is limited to 700 mA typical,
and the IC will be shut down if the overcurrent condition lasts
for more than 48 ms. If this occurs, the A8293 must be reenabled
for normal operation. The system should provide sufficient time
between successive restarts to limit internal power dissipation; a
minimum of 2 s is recommended.
At extremely light loads, the boost converter operates in a
pulse-skipping mode. Pulse skipping occurs when the BOOST
voltage rises to approximately 450 mV above the BOOST target
output voltage. Pulse skipping stops when the BOOST voltage
drops 200 mV below the pulse skipping level.
In the case that two or more set top box LNB outputs are con-
nected together by the customer (e.g., with a splitter), it is pos-
sible that one output could be programmed at a higher voltage
than the other. This would cause a voltage on one output that is
higher than its programmed voltage (e.g., 19 V on the output of a
13 V programmed voltage). The output with the highest voltage
will effectively turn off the other outputs. As soon as this voltage
is reduced below the value of the other outputs, the A8293 output
will auto-recover to their programmed levels.
Charge Pump. Generates a supply voltage above the internal
tracking regulator output to drive the linear regulator control.
Slew Rate Control. During either start-up, or when the output
voltage at the LNB pin is transitioning, the output voltage rise
and fall times can be set by the value of the capacitor connected
from the TCAP pin to GND (C TCAP or C7 in the Applications
Schematic). Note that during start-up, the BOOST pin is pre-
charged to the input voltage minus a voltage drop. As a result,
the slew rate control for the BOOST pin occurs from this voltage.
The value of C TCAP can be calculated using the following for-
mula:
C TCAP = ( I TCAP × 6) / SR ,
where SR is the required slew rate of the LNB output voltage,
in V/s, and I TCAP is the TCAP pin current specified in the data
sheet. The recommended value for C TCAP , 10 nF, should provide
satisfactory operation for most applications. However, in some
cases, it may be necessary to increase the value of C TCAP to avoid
activating the current limit of the LNB output. One such situa-
tion is when two set-top boxes are connected in parallel. If this is
the case, the following formula can be used to calculate C TCAP :
C TCAP ≥ (I TCAP × 6)(2 × C BOOST ) / I LIMLNB ,
C TCAP ≥ (10 μ A × 6)(2 × 100 μ F) / 500 mA = 24 nF .
The minimum value of C TCAP is 2.2 nF. There is no theoretical
maximum value of C TCAP however too large a value will prob-
ably cause the voltage transition specification to be exceeded.
Tone generation is unaffected by the value of C TCAP .
Pull-Down Rate Control. In applications that have to operate at
very light loads and that require large load capacitances (in the
order of tens to hundreds of microfarads), the output linear stage
provides approximately 40 mA of pull-down capability. This
ensures that the output volts are ramped from 18 V to 13 V in a
reasonable amount of time.
ODT (Overcurrent Disable Time)
If the LNB output current exceeds 700 mA, typical, for more than
48 ms, then the LNB output will be disabled and the OCP bit will
be set.
Short Circuit Handling
If the LNB output is shorted to ground, the LNB output current
will be clamped to 700 mA, typical. If the short circuit condition
lasts for more than 48 ms, the A8293 will be disabled and the
OCP bit will be set.
Auto-Restart
After a short circuit condition occurs, the host controller should
periodically reenable the A8293 to check if the short circuit has
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
6
相关PDF资料 |
PDF描述 |
|---|---|
| A8436EEJTR-T | IC PHOTOFLASH CHARGER 10-MLP |
| A8437ECGLT | IC PHOTOFLASH CAP CHARGER WLCSP |
| A8438EEJTR-T | IC PHOTOFLASH CHARGER 10-MLP |
| A8439EEJTR-T | IC CHARGER PHOTO FLASH 10-MLP |
| A8447SLJTR-T | IC REG BUCK ADJ 3A 8SOIC |
相关代理商/技术参数 |
参数描述 |
|---|---|
| A8294 | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:Single LNB Supply and Control Voltage Regulator |
| A8294SESTR-T | 功能描述:IC REG LNB SGL SUPPLY QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 专用型 系列:- 标准包装:43 系列:- 应用:控制器，Intel VR11 输入电压:5 V ~ 12 V 输出数:1 输出电压:0.5 V ~ 1.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:48-VFQFN 裸露焊盘 供应商设备封装:48-QFN（7x7） 包装:管件 |
| A8295SESTR-T | 功能描述:IC REG LNB SGL SUPPLY 20-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 专用型 系列:- 标准包装:43 系列:- 应用:控制器，Intel VR11 输入电压:5 V ~ 12 V 输出数:1 输出电压:0.5 V ~ 1.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:48-VFQFN 裸露焊盘 供应商设备封装:48-QFN（7x7） 包装:管件 |
| A82963-000 | 制造商:TE Connectivity 功能描述:VARISTOR 39V 7MM RADIAL T/R 制造商:TE Connectivity 功能描述:VARISTOR 39V 250A DISC 7MM 制造商:TE CONNECTIVITY RAYCHEM-POLYSWITCH 功能描述:Var MOV 25VAC 31VDC 250A 39V Thru-Hole T/R |
| A8296SESTR-T | 功能描述:IC REG LNB SGL SUPPLY 16-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 专用型 系列:- 标准包装:43 系列:- 应用:控制器，Intel VR11 输入电压:5 V ~ 12 V 输出数:1 输出电压:0.5 V ~ 1.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:48-VFQFN 裸露焊盘 供应商设备封装:48-QFN（7x7） 包装:管件 |
发布紧急采购，3分钟左右您将得到回复。