M66515FP
Block Diagram
Explanation of operation
1. Laser driving current values
The values of the laser driving currents I
SW
and I
B
can be approximated as follows, if V
C
is the voltage of the hold
capacitor connected to the C
H
pin.
(1) I
SW
(switched current)
Here 0≤V
C
≤V
CC
-1.8 V, I
SW
(max) =120 mA, and R
S
is the value of the resistance connected between the R
S
pin and
GND
(2) I
B
(bias current)
Here 0≤V
B
≤V
CC
-2.7 V, I
B
(max) =30 mA, and R
B
is the value of the resistance connected between the R
B
pin and GND
2. Switching operation
When
DATA="L",
the LD driving current is I
SW
+I
B
; when
DATA="H",
the LD driving current is I
B
.
3.
ENB
input
Whereas the laser driving current is controlled by
DATA
input by controlling the driving current applied to the laser
with the current source in the M66515 turned on, control by
ENB
turns the current source operation on and off.
When
ENB="L"
the current source is turned on, and when
ENB="H"
the current source is turned off.
When
ENB="H",
the C
H
pin is forced to "L" level, and the charge on the capacitor connected to the C
H
pin is forcibly
discharged.
4. Internal reset operation
The M66515 incorporates a reset circuit to prevent the flow of excessive current to the laser when power is turned on;
when V
CC
<3.5 V (typ), the internal current source is turned off and the C
H
pin is forced to "L" level.
Rev.1.00, Sep.22.2003, page 3 of 11
RENESAS [ RENESAS TECHNOLOGY CORP ]
