MAX3265 MAXIM [Maxim Integrated Products], MAX3265 Datasheet - Page 10

• Manufacturer Part Number: MAX3265
• Description: 3.0V to 5.5V, 1.25Gbps/2.5Gbps Limiting Amplifiers
• Manufacturer: MAXIM [Maxim Integrated Products]

+3.0V to +5.5V, 1.25Gbps/2.5Gbps
Limiting Amplifiers
Figure 3 is a functional diagram of the MAX3264/
MAX3265/MAX3268/MAX3269/MAX3765/MAX3768 lim-
iting amplifiers. A linear input buffer drives a multistage
limiting amplifier and an RMS power-detection circuit.
Offset correction with lowpass filtering ensures low
deterministic jitter. The output buffer produces a limited
output signal. The MAX3264/MAX3265/MAX3765 pro-
duce a CML output, while the MAX3268/MAX3269/
MAX3768 produce a PECL-compatible output signal.
Schematics of these input/output circuits are shown in
Figures 4 through 7.
Figure 3. Functional Diagram
10
_______________Detailed Description
______________________________________________________________________________________
IN+
IN-
TOTAL GAIN = 55dB (MAX3264/MAX3268/MAX3768)
TOTAL GAIN = 49dB (MAX3265/MAX3269/MAX3765)
100
MAX3264
MAX3265
MAX3268
MAX3269
MAX3765
MAX3768
BUFFER
INPUT
CORRECTION
OFFSET
POWER DETECT
COMPARATOR
WITH
TH
CAZ1
R
R
LOS
LOS
GAIN
100pF
LOW-
PASS
= 8k (MAX3265/MAX3269/MAX3765)
= 16k (MAX3264/MAX3268/MAX3768)
CAZ2
An RMS power detector looks at the signal from the
input buffer and compares it to a threshold set by the
TH resistor (see Typical Operating Characteristics for
appropriate resistor values). The signal-detect informa-
tion is provided to the LOS outputs, which are internally
terminated with 8k
16k
The LOS outputs meet TTL voltage specifications when
loaded with a resistor
(MAX3264/MAX3268/MAX3768) pullup resistors.
TTL
TTL
(MAX3265/MAX3269/MAX3765) or
CONTROL
OUTPUT
BUFFER
V
V
CC
CC
4.7k .
RMS Power Detect with
Loss-of-Signal Indicator
R
R
LOS
LOS
LOS
LOS
OUT+
OUT-
SQUELCH
LEVEL