M66510 Просмотр технического описания (PDF) - MITSUBISHI ELECTRIC

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M66510

LASER-DIODE DRIVER

MITSUBISHI ELECTRIC  

MITSUBISHI 〈DIGITAL ASSP〉

M66510P/FP

LASER-DIODE DRIVER

5. 1RO/2RO pin

The 1RO pin is used to connect the load resistor (RO1) for

current source 1 (IL1). The 2RO pin is used to connect the

load resistor (RO2) for current sources 2 (IL2) and 3 (IL3).

Connecting the load resistor between each pin and Vcc re-

duces IC internal power dissipation.

Set a resistance value so that each pin voltage does not go

down to 3.5V or less. In other words, set a value such as

meets the following expression:

RO1(RO2)[Ω] ≤

VCC – 3.5[V]

Maximum load current [A] flowing into RO1(RO2)

Ex: When VCC = 5V and maximum load current of each source is 60mA, RO1

and RO2 will be 25Ω or less.

6. Internal reset operation

The M66510 is provided with an internal reset circuit to pre-

vent overcurrent from flowing into the laser at the power-ON

time. The reset circuit operates within the range of VCC <

3.5V (standard) to turn off all the current sources.

7. VCC/GND pin

The power supply pins include VCC1, VCC2, GND1 and

GND2, each of which is as follows in terms of internal circuit:

VCC1/GND1: Connected to an analog circuit.

VCC2/GND2: Connected to a digital circuit.

In actual wiring, pay attention to the following:

(1) Make wiring width as wide as possible. Avoid redundant

wiring.

(2) Lay out an electrolytic capacitor for stabilizing voltage as

close to VCC1/GND1 as possible.

(3) Lay out a bypass capacitor as close to VCC2/GND2 as

possible.

Precaution for peripheral element wiring

Lay out the peripheral elements required for M66510 opera-

tion as close to M66510 as possible.

Method of calculating power dissipation

The power dissipation P of M66510 is given by the expres-

sion given below.

P = ICC × VCC + I(1RO) × (V(1RO) – V(LD)) + I(2RO) × (V(2RO) –

V(LD)) + IOL(CO) × VOL(CO)

where, V(1RO) : 1RO pin voltage

V(2RO) : 2RO pin voltage

I(1RO) : 1RO pin load current

I(2RO) : 2RO pin load current

V(LD) : LD pin voltage

IOL(CO) : CO pin “L” output current

VOL(CO) : CO pin “L” output voltage

For example, when VCC = 5.25V, V(1RO) = V(2RO) = 3.5V,

I(1RO) = I(2RO) = 60mA, V(LD) = 2.5V, IOL(CO) = 8mA and

VOL(CO) = 0.5V, the power dissipation at the laser-ON/OFF

time is as follows:

(1) Laser-ON time (DATA = “L”, ICC=26mA)

PON = 26 × 5.25 + 60 × (3.5 – 2.5) + 60 × (3.5 – 2.5) + 8 × 0.5

= 260.5(mW)

(2) Laser-OFF time (DATA = “H”, ICC = 44mA)

POFF = 44 × 5.25 + 0 + 0 + 8 × 0.5 = 235(mW)

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