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参数资料
| 型号： | DS1878T+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 10/101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： | 2,500 |
| 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： | 带卷 (TR) |
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DS1878
SFP+ Controller with Digital LDD Interface
16
______________________________________________________________________________________
An APC sample that requires an update of the BIAS
register causes subsequent APC samples to be
ignored until the end of the 3-wire communication that
updates the laser driver’s BIAS DAC, plus an additional
16 sample periods (tREP).
Monitors and Fault Detection
Monitors
Monitoring functions on the device include five quick-trip
comparators and six ADC channels. This monitoring
combined with the alarm enables (Table 01h/05h) deter-
mines when/if the device turns off the Maxim laser dri-
ver’s DACs and triggers the TXFOUT and TXDOUT
outputs. All the monitoring levels and interrupt masks are
user programmable.
Five Quick-Trip Monitors and Alarms
Five quick trip monitors are provided to detect potential
laser safety issues and LOS status. These monitor the
following:
1) High Bias Current (HBATH), causing QT BIAS HI
2) Low Transmit Power (LTXP), causing QT TXP LO
3) High Transmit Power (HTXP), causing QT TXP HI
4) Max Output Current (IBIASMAX), causing QT BIAS
MAX
5) Loss of Signal (LLOS), causing QT LOS LO
The high and low transmit power quick-trip registers
(HTXP and LTXP) set the thresholds used to compare
against the MON2 voltage to determine if the transmit
power is within specification. The HBATH quick trip
compares the MON1 input (generally from a Maxim
laser driver bias monitor output) against its threshold
setting to determine if the present bias current is above
specification. The user can program up to eight differ-
ent temperature-indexed threshold levels for HBATH
(Table 02h, Registers D0h–D7h).
The BIAS MAX quick trip compares the BIAS register
with the MON2 voltage and determines if the BIAS reg-
ister is above specification. The BIAS register is not
allowed to exceed the value set in the IBIASMAX regis-
ter. When the device detects the bias is at the limit, it
sets the BIAS MAX status bit and holds the BIAS regis-
ter setting at the IBIASMAX level.
The LOS LO quick trip compares the MON3 input
against its threshold setting (LLOS) to determine if the
present received power is below the specification. The
LOS RANGING register allows the LOS threshold value
to scale. The LOS LO quick trip can be used to set the
LOSOUT pin. LOS HI does not set LOSOUT. See the
description of the LOS LO and LOS HI bits (Table 01h,
Register FBh) for further details of operation.
The quick trips are routed to create TXFOUT through
interrupt masks to allow combinations of these alarms
to be used to trigger the outputs.
Six ADC Monitors and Alarms
The ADC monitors six channels that measure tempera-
ture (internal temp sensor), VCC, and MON1–MON4
using an analog multiplexer to measure them round
robin with a single ADC (see the
ADC Timing section).
The five voltage channels have a customer-programma-
ble full-scale range and all channels have a customer-
programmable offset value that is factory programmed to
default value (see Table 3). Additionally, MON1–MON4
can right-shift results by up to 7 bits before the results
are compared to alarm thresholds or read over the I2C
bus. This allows customers with specified ADC ranges to
calibrate the ADC full scale to a factor of 1/2n of their
specified range to measure small signals. The device
can then right-shift the results by n bits to maintain the bit
weight of their specification (see the
Right-Shifting ADC
Result and Enhanced RSSI Monitoring (Dual-Range
Functionality) sections).
The ADC results (after right-shifting, if used) are com-
pared to the alarm and warning thresholds after each
conversion, and the corresponding alarms are set,
which can be used to trigger the TXFOUT output.
These ADC thresholds are user programmable, as are
the masking registers that can be used to prevent the
alarms from triggering the TXFOUT output.
ADC Timing
There are six analog channels that are digitized in a
round-robin fashion in the order shown in Figure 5. The
total time required to convert all six channels is tRR (see
the
Analog Voltage Monitoring Characteristics for
details).
Table 3. ADC Default Monitor Full-Scale Ranges
SIGNAL (UNITS)
+FS SIGNAL
+FS HEX
-FS SIGNAL
-FS HEX
Temperature (°C)
127.996
7FFF
-128
8000
VCC (V)
6.5528
FFF8
0
0000
MON1–MON4 (V)
2.4997
FFF8
0
0000
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