TZA3033T/C3,112 NXP Semiconductors, TZA3033T/C3,112 Datasheet - Page 6

• Manufacturer Part Number: TZA3033T/C3,112
• Manufacturer: NXP Semiconductors

Specifications of TZA3033T/C3,112

• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 8
• Lead Free Status / RoHS Status: Compliant

Philips Semiconductors
PIN diode bias voltage DREF
The transimpedance amplifier together with the PIN diode
determine to a large extent the performance of an optical
receiver. The key parameters of a transimpedance
amplifier like sensitivity, bandwidth, and the Power Supply
Rejection Ratio (PSSR), are especially influenced by how
the PIN diode is connected to the input and the layout
around the input pin. The total capacitance at the input pin
is critical to obtain the highest sensitivity. It should be kept
to a minimum by reducing the capacitor of the PIN diode
and the parasitics around the input pin. The PIN diode
should be placed very close to the IC to reduce the
parasitics. Because the capacitance of the PIN diode
depends on the reverse voltage across it, the reverse
voltage should be selected as high as possible.
The PIN diode can be connected to the input as shown in
Fig.5. In Fig.5 the PIN diode is connected between DREF
and IPhoto. Pin DREF provides an easy bias voltage for
the PIN diode. The voltage at DREF is derived from V
a low-pass filter. The low-pass filter consisting of the
internal resistor R1, the internal capacitor C1 and the
external capacitor C2 rejects the supply voltage noise. The
external capacitor C2 should be equal to or larger than
1 nF for a high PSRR.
It is preferable to connect the cathode of the PIN diode to
a voltage higher than V
available on the board. In this case the DREF pin can be
left unconnected.
The reverse voltage across the PIN diode is 3.95 V
(5
a 3.3 V supply.
2002 Sep 06
SDH/SONET STM1/OC3
transimpedance amplifier
1.05 V) for a 5 V supply and 2.25 V (3.3
CC
when such a voltage source is
1.05 V) for
CC
by
6
Fig.5 Connecting the PIN diode to the input.
1 nF
C2
I i
IPhoto
DREF
1
3
C1
65 pF
250
R1
Product specification
V CC
TZA3033
8
TZA3033
MGT548