spt9101 Fairchild Semiconductor, spt9101 Datasheet - Page 6

• Manufacturer Part Number: spt9101
• Description: 125 Msps Sample-and-hold Amplifier
• Manufacturer: Fairchild Semiconductor

The RTN pin may be tied to an external voltage to generate
an offset at the output. V
typical output swing. V
at the RTN pin, is represented by the following formula:
The following options are generally not recommended due to
the possibility of degraded noise performance of the device:
the RTN pin can also be tied to an external resistor to reduce
the gain but performance may degrade due to increased
noise from the external resistor. Also RTN can be left open for
unity gain mode, however, noise will increase.
In all cases, V
performance.
V
where V
Out
-120
-75
-70
-65
-60
-55
-40
-80
40
0
SPT9101 Hold Mode Distortion vs Input Frequency
= 4 V
1
Ref
Clock Frequency = 100 MHz
Track = 6 ns
Hold = 4 ns
IN
IN
= voltage at RTN pin and | V
-20
- 3 V
must be kept to -0.5 V V
Droop Rate vs Temperature
Ref
Input Frequency (MHz)
Out
0
Out
, with an external reference voltage
Temperature (°C)
must be kept to less than 2.7 V
20
10
Worst Harmonic
PERFORMANCE CHARACTERISTICS
40
IN
Out
+0.5 V for rated
60
|
2.7 V
100
80
6
SAMPLER FOR 12-BIT ADC APPLICATION
The SPT9101 was specifically designed for applications
where improved bandwidth performance is required. Figure 3
shows as simple block diagram of the SPT9101 as a sampler
ahead of the SPT7922 12-bit, 30 MSPS ADC.
Figure 3 - Sampler for 12-Bit ADC
The graph below entitled Improved Dynamic Performance
Using the SPT9101 shows the performance with and without
the SPT9101. The SPT9101 significantly extends the dy-
namic performance range of the converter.
V IN
-65
-60
70
60
50
40
Improved Dynamic Performance Using the SPT9101
-50
SPT9101 Hold Mode Distortion vs. Temperature
(F S = 28 MSPS)
-25
SPT9101
Clock 1
Worst Harmonic
5
0
Temperature (°C)
F IN (MHz)
SPT9101 & SPT7922
SPT7922
10
25
Input Frequency = 50 MHz
Clock Frequency = 100 MHz
Hold = 4 ns
Track = 6 ns
50
SPT7922
15
Clock 2
75
SPT9101
20
12
100
12/30/99