MAX3967 查看數據表（PDF） - Maxim Integrated

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MAX3967

270Mbps SFP LED Driver

Maxim Integrated 

270Mbps SFP LED Driver

PIN

1

2

3, 4, 5

6, 7

8, 9

10, 11

12, 16

13, 14

15, 19

17

18

20

21

22

23

24

Pin Description

NAME

FUNCTION

TCNOM Shorting TC to TCNOM provides a modulation tempco of approximately 3600 ppm/°C.

TC

A resistor (RTC) connected between the TC and TCMIN pins sets the tempco of the modulation

current. Leaving RTC unconnected provides the maximum tempco.

PB1, PB2, PB3 Programs the Prebias Voltage at the OUT+ Pin (Table 1)

VEEOUT

Ground for the Output-Current Drivers

OUT+

Current Output Pins

OUT-

Complementary Current Output Pins

N.C.

Not Connected

VCCOUT

Supply Connection for the Output-Current Drivers

VCC

Provides Current to the Internal Amplifiers

MON

The Current Sourced from the MON Pin is Proportional to the Modulator Current

MODSET A Resistor from MODSET to VEE Programs the LED Modulation Current

IN-

Inverting Data Input

IN+

Noninverting Data Input

TX_DISABLE

Transmit Disable. When high, the current at the OUT+ pins is in the low state. The transmitter is

enabled when TX_DISABLE is open.

VEE

Ground for internal amplifiers.

TCMIN

Shorting TC to TCMIN provides the minimum modulation-current tempco.

Detailed Description

The MAX3967 provides a flexible current drive for the

modulation of fiber optic light-emitting diodes (LEDs).

The circuit is designed to be used with +3.3V or +5V

power supplies. The IC provides up to 100mA of modu-

lation current. An adjustable prebias current source

sets the LED prebias voltage. An integrated resistor

provides passive peaking and optical pulse-width com-

pensation.

Figure 2 shows a block diagram of the MAX3967, which

comprises a reference-voltage generator, modulation-

current generator, input buffer with disable, prebias-

current generator, main output driver, complementary

output driver, and LED-compensation network.

Temperature Compensation

The reference-voltage generator circuit provides two

voltage sources that create modulation-current temper-

ature compensation. A positive modulation-current tem-

perature coefficient (tempco) is useful to compensate

for the temperature characteristics of typical fiber optic

LEDs. The first source has a temperature-stable output.

The second source has a temperature-increasing out-

put with a tempco of approximately 12,000ppm/°C (rel-

ative to +25°C). A resistor-divider between the two

reference generators programs the modulation-current

tempco. For maximum modulation-current tempco,

leave the TC pin disconnected. For a tempco of

approximately 3600ppm/°C, connect TC to TCNOM. To

obtain the minimum tempco, connect TCMIN to TC.

Intermediate tempco values can be programmed by

connecting an external resistor (RTC) between TCMIN

and TC.

Input Buffer

The inputs are connected to the PECL-compatible dif-

ferential input buffer. If left unconnected, IN+ is internal-

ly pulled to a PECL low and IN- is pulled to a PECL

high, causing low current at OUT+. The input imped-

ance of IN+ and IN- is approximately 50kΩ.

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