The DS1874 controls and monitors all functions for SFF, SFP, and SFP+ modules including all SFF-8472 functionality. The combination of the DS1874 with the MAX3798/MAX3799 laser driver/limiting amplifier provides APC loop, modulation current control, and eye safety functionality. The DS1874 continuously monitors for high output current, high bias current, and low and high transmit power to ensure that laser shutdown for eye safety requirements are met without adding external components. Six ADC channels monitor VCC, temperature, and four external monitor inputs (MON1–MON4) that can be used to meet all monitoring requirements. MON3 is differential with support for common mode to VCC. Two digital-to-analog (DAC) outputs with temperature-indexed lookup tables (LUTs) are available for additional monitoring and control functionality.
Key Features
Applications/Uses
Meets All SFF-8472 Control and Monitoring Requirements
Laser Bias Controlled by APC Loop and Temperature LUT to Compensate for Tracking Error
Laser Modulation Controlled by Temperature LUT
Six Analog Monitor Channels: Temperature, VCC, MON1–MON4
MON1–MON4 Support Internal and External Calibration
Scalable Dynamic Range
Internal Direct-to-Digital Temperature Sensor
Alarm and Warning Flags for All Monitored Channels
Two 9-Bit Delta-Sigma Outputs with 36 Entry Temperature LUTs
Digital I/O Pins: Five Inputs, Five Outputs
Comprehensive Fault-Measurement System with Maskable Laser Shutdown Capability
Flexible, Two-Level Password Scheme Provides Three Levels of Security
256 Additional Bytes Located at A0h Slave Address
I²C-Compatible Interface
3-Wire Master to Communicate with the MAX3798/MAX3799 Laser Driver/Limiting Amplifier
* Some packages have variations, listed on the drawing. "PkgCode/Variation" tells which variation the product uses. Note that "+", "#", "-" in the part number suffix describes RoHS status. Package drawings may show a different suffix character.
Devices:
1-2 of 2
DS1874
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TYPE PINS FOOTPRINT
DRAWING CODE/VAR *
Temp
RoHS/Lead-Free? Materials Analysis
DS1874T+
Active
TQFN;28 pin;26 mm²
Outline Drawing: 21-0140 (PDF)
Land Pattern: 90-0026 (PDF)
Use pkgcode/variation: T2855+6*
DS1856 Dual, Temperature-Controlled Resistors with Internally Calibrated Monitors and Password Protection DS1873 SFP+ Controller with Analog LDD Interface MAX3798 1.0625Gbps to 10.32Gbps, Integrated, Low-Power SFP+ Limiting Amplifier and VCSEL Driver
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