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参数资料
| 型号： | A8285SLBTR-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 7/18页 |
| 文件大小： | 0K |
| 描述： | IC LNB SUPPLY/VOLTAGE REG 16SOIC |
| 标准包装： | 1 |
| 应用： | 转换器，模拟和数字式卫星信号接收器 |
| 输入电压： | 6 V ~ 16 V |
| 输出数： | 1 |
| 输出电压： | 12.7 V ~ 20.4 V |
| 工作温度： | -20°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-SOIC（0.295"，7.50mm 宽） |
| 供应商设备封装： | 16-SOIC W |
| 包装： | 标准包装 |
| 产品目录页面： | 1141 (CN2011-ZH PDF) |
| 其它名称： | 620-1202-6 |
A8285 and
A8287
LNB Supply and Control Voltage Regulator
Functional Description
Boost Converter/Linear Regulator . A current-mode boost
converter provides the tracking regulator a supply voltage that
tracks the requested LNB output voltage. The converter operates
at 16 times the internal tone
frequency, 352 kHz nominal.
The tracking regulator provides minimum power dissipation
across the range of output voltages, assuming the input voltage is
less than the output voltage, by adjusting the BOOST pin voltage
600 mV nominal above the LNB output voltage selected. Under
conditions where the input voltage is greater than the output
voltage, the tracking regulator must drop the differential voltage.
When operating in this condition, care must be taken to ensure
that the safe operating temperature range of the A8285/A8287 is
not exceeded. For additional information, see Power Dissipation
in the Application Information section.
Note: To conserve power at light loads, the boost converter oper-
ates in a pulse-skipping mode.
Overcurrent Protection. The A8285/A8287 is protected
against both overcurrent and short circuit conditions by limit-
ing the output current to I LIM . In the event of an overcurrent,
the current limit can be applied indefinitely. Alternatively, if
the ODT feature is enabled, and the fault current appears for
longer than the disable time t DIS , then the device is turned off.
The device can be enabled again via the I 2 C? interface. If the
overcurrent is removed before the disable time has elapsed, the
device remains functioning. These settings are made in the Con-
trol register and the Status register.
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 on the BOOST pin is being changed, the output voltage
rise and fall times can be programmed by an external capacitor
located on the TCAP pin. Note that during start-up, the BOOST
pin is precharged to the input voltage minus a diode drop. As a
result, the slew rate control occurs from this point.
The value for TCAP can be calculated using the following for-
mula:
TCAP = (I CAP × 8) / ( Δ V/s)
where Δ V/s is required slew rate. The smallest value for TCAP
is 2.2 nF.
Modulation is unaffected by the choice of TCAP. If limiting
LNB output voltage rise and fall times is not required, the TCAP
terminal must have a value of at least a 2.2 nF to minimize
output noise.
External Tone Modulation . To improve design flexibility
and to allow implementation of proposed LNB remote control
standards, the logic modulation input pin EXTM is provided.
The logic signal supplied to this pin creates a 650 mV ±250 mV
tone signal on the TOUT pin by controlling a 40 mA current
pull-down device through the
DiSEqC? filter. The shape of the tone waveform depends on the
filter components used and the LNB/cable capacitance.
Tone Detection . A 22 kHz tone envelope detector is provided
in the A8287 solution. The detector extracts the tone signal and
provides it as an open-collector signal on the TDO pin. The maxi-
mum tone out error is ±1 tone cycle, and the maximum tone out delay
with respect to the input is ±1 tone cycle.
Control Register . The main functions of the A8285/A8287
are controlled via the I 2 C interface by writing to the control
register. The power-up states for the control functions are all
zero. Control functions include the following:
? Internal Tone Modulation Enable (ENT) . When the
ENT bit is set to 1, the internal tone generator controls a 40
mA pull-down device, thus creating the tone signal after the
DiSEqC? filter in a way identical to the EXTM scheme. The
internal oscillator is factory-trimmed to provide a tone of 22 ±2
kHz. No further adjustment is required. Burst coding of the 22
kHz tone is accomplished due to the fast response of the serial
command and rapid tone response. This allows implementation
of the
DiSEqC? 2.0 protocols.
? Select Output Voltage Amplitude (VSEL0, VSEL1, VSEL2,
VSEL3). The LNB output voltage can be programmed to a partic-
ular voltage according to the Output Voltage Amplitude Selection
table shown on the following page.
? Enable (ENB) . When set to 1, the LNB output is enabled.
When reset to 0, the LNB output is disabled.
? Overcurrent Limit (I LIM ) . Selects the output overcurrent limit.
When set to 0, the limit is 500 mA. When set to 1, the limit is 700
mA.
? Overcurrent Disable Time (ODT) . When set to 1, in the
event of an overcurrent occuring for a duration exceeding the
disable time, the device is turned off. When set to 0,
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
7
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相关代理商/技术参数 |
参数描述 |
|---|---|
| A8286 | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:Dual LNB Supply and Control Voltage Regulator |
| A8286SETTR-T | 功能描述:IC REG LNB SUPPLY/CONTROL 28-MLP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 专用型 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,000 系列:- 应用:电源，ICERA E400，E450 输入电压:4.1 V ~ 5.5 V 输出数:10 输出电压:可编程 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:42-WFBGA，WLCSP 供应商设备封装:42-WLP 包装:带卷 (TR) |
| A8286SETTR-TB | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:Dual LNB Supply and Control Voltage Regulator |
| A8286SLBTR-T | 制造商:Allegro MicroSystems LLC 功能描述: |
| A8287 | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:LNB Supply and Control Voltage Regulator |
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