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| 型号： | DS1878T+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 8/101页 |
| 文件大小： | 0K |
| 描述： | IC CTLR SFP W/DGTL LDD RX 28TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 60 |
| 类型： | SFP+ 控制器 |
| 输入类型： | 模拟，数字 |
| 输出类型： | 数字 |
| 接口： | I²C，LDD，串行 |
| 电流 - 电源： | 2.5mA |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-WFQFN 裸露焊盘 |
| 供应商设备封装： | 28-TQFN-EP（5x5） |
| 包装： | 托盘 |
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DS1878
SFP+ Controller with Digital LDD Interface
14
______________________________________________________________________________________
(MODTC, Table 02h, Register C6h) and a temperature
index register (MODTI, Table 02h, Register C2h).
BIAS and MODULATION Control
During Power-Up
The device has two internal registers, MODULATION
and BIAS, that represent the values written to the Maxim
laser driver’s modulation DAC and bias DAC through
the 3-wire interface. On power-up, the device sets the
MODULATION and BIAS registers to 0. When VCC is
above POA, the device initializes the Maxim laser driver.
After a temperature conversion is completed and if the
VCC LO alarm is enabled, an additional VCC conversion
above the customer-defined VCC LO alarm level is
required before a Maxim laser driver MODULATION
register is updated with the value determined by the
temperature conversion and the modulation LUT.
When the MODULATION register is set, the BIAS regis-
ter is set to a value equal to ISTEP (see Figure 2). The
startup algorithm verifies whether this bias current caus-
es a feedback voltage above the APC set point, and if
not, it continues increasing the BIAS register by ISTEP
until the APC set point is exceeded. When the APC set
point is exceeded, the device begins a binary search to
quickly reach the bias current corresponding to the
proper power level. After the binary search is complet-
ed, the APC integrator is enabled and single LSB steps
are used to tightly control the average power.
The TXP HI, TXP LO, and BIAS MAX QT alarms are
masked until the binary search is completed. However,
the BIAS MAX alarm is monitored during this time to
prevent
the
BIAS
register
from
exceeding
IBIASMAX. During the bias current initialization, the
BIAS register is not allowed to exceed IBIASMAX. If this
occurs during the ISTEP sequence, then the binary
search routine is enabled. If IBIASMAX is exceeded
during the binary search, the next smaller step is acti-
vated. ISTEP or binary increments that would cause the
BIAS register to exceed IBIASMAX are not taken.
Masking the alarms until the completion of the binary
search prevents false positive alarms during startup.
ISTEP is a value controlled by registers ISTEPH,
ISTEPL, and ISTEPTI (Table 02h, Registers BAh, BBh,
and C5h, respectively). See the register descriptions for
more information. During the first steps, a Maxim laser
driver’s bias DAC is directly written using SET_IBIAS.
ISTEP should be programmed to the maximum safe
increase that is allowable during startup. If this value is
programmed too low, the device still operates, but it
could take significantly longer for the algorithm to con-
verge and hence to control the average power.
If a fault is detected, and TXD is toggled to reenable
the outputs, the device powers up following a similar
sequence to an initial power-up. The only difference is
that the device already has determined the present
12
3
4
56
7
89
10
11
12
13
VPOA
MODULATION REGISTER
BIAS REGISTER
VCC
BIAS SAMPLE
tINIT
tSEARCH
BINARY SEARCH
APC INTEGRATOR ON
4x ISTEP
3x ISTEP
2x ISTEP
ISTEP
Figure 2. Power-Up Timing
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相关代理商/技术参数 |
参数描述 |
|---|---|
| DS1878T TR | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:SFP+ Controller with Digital LDD Interface |
| DS1878T+ | 功能描述:ADC / DAC多通道 SFP+ Controller w/ MAX3946&3945 RoHS:否 制造商:Texas Instruments 转换速率: 分辨率:8 bit 接口类型:SPI 电压参考: 电源电压-最大:3.6 V 电源电压-最小:2 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-40 |
| DS1878T+T | 功能描述:ADC / DAC多通道 SFP+ Controller w/ MAX3946&3945 RoHS:否 制造商:Texas Instruments 转换速率: 分辨率:8 bit 接口类型:SPI 电压参考: 电源电压-最大:3.6 V 电源电压-最小:2 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-40 |
| DS1878T+T&R | 制造商:Maxim Integrated Products 功能描述:IC CTLR SFP W/DGTL LDD RX 28TQFN |
| DS1878T+T&R | 功能描述:ADC / DAC多通道 SFP+ Controller w/ MAX3946&3945 RoHS:否 制造商:Texas Instruments 转换速率: 分辨率:8 bit 接口类型:SPI 电压参考: 电源电压-最大:3.6 V 电源电压-最小:2 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-40 |
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