sp8034 Exar Corporation, sp8034 Datasheet - Page 3

• Manufacturer Part Number: sp8034
• Description: 250 V/?s Apc Amplifier With Integrated Photodiode And Gain Adjust Capability
• Manufacturer: Exar Corporation

* V
Rev. 5/21/03
The SP8034 is an Automatic Power Control
(APC) circuit for pick-up head applications.
The part consists of a photo-detector that con-
verts the light (780nm or 650nm) into current,
and active circuitry (transimpedance amp-
lifier and buffer) to convert the current into
voltage. The overall transfer characteristics are
therefore represented by a Voltage per Watt
curve.
There are three pins for gain adjust, using two
separate external resistors for two separate gain
modes. This allows different adjust for a DVD
and a CD mode.
The two resistors are each tied from the corres-
ponding RG pin (pin 5 or 6, depending on the
mode) to the common gain pin (pin 3). The gain
adjust is proportional to the external resistance
and is done by means of an analog duplication
circuit that translates the resistance value in an
active feedback circuit at the transimpedance
amplifier. The fact that the external resistor is
not in the signal path ensures a better signal
quality and immunity to the parasitic capacit-
ance/inductance on the pins 3,5 and 6.
In dark condition, the output of the circuit will
remain at the externally supplied V
2.3V). When light (650nm or 780nm) is re-
ceived on the photo-diode, the output (V
8) will swing negative with respect to V
The output swing is guaranteed to be at least
1.5V from V
the output can swing at least as low as 0.5V
(absolute).
Table 1. Target Gain Set Points for the System.
PIN NUMBER
CC
Gain (dB)
≥ 5.0V
-6 *
+6
-3
0
1
2
3
4
5
6
7
8
REF
. For example, with V
Sensitivity (mV/mW)
NAME
RG
1.4
R
R
GAIN
4
2
1
GND
V
V
V
GAIN1
GAIN2
REF
OUT
CC
COM
SP8034 APC Amplifier with Integrated Photodetector
REF
REF
(1.9V ≥
OUT
at 2V,
, pin
Supply Voltage
GAIN Select
Common connection point for R
Power Ground
Gain Adjust 1(Gain Select = LOW)
Gain Adjust 2 (Gain Select = HIGH)
Reference Voltage
Output Voltage
REF
Regain (
FUNCTION
.
950
400
250
150
3
Ω
Figure 3. System Bandwith versus Gain Resistor,
V
Figure 2. Sensitivity vs. Gain Resistor (Absolute)
)
CC
3
2
0
5
= 5V, T = 27C.
5000
4500
4000
3500
2000
1500
1000
0
0
0
0
0
0
95.0M
90.0M
85.0M
80.0M
75.0M
70.0M
65.0M
60.0M
55.0M
50.0M
45.0M
Ts(nS) 1%
100M
100
0.0
13
12
10
11
200
200
300
THEORY OF OPERATION
GAIN1
Gain Adjust Resistor (Ω)
400
400
© Copyright 2003 Sipex Corporation
R
BW (MHz)
and R
GAIN
500
PIN DESCRIPTION
600
61
79
87
93
600
GAIN2
700
800
800
1.0K
Pin(uW)
1070
1500
900
380
750
1000