MAX4215EUA+ Maxim Integrated Products, MAX4215EUA+ Datasheet - Page 11

• Manufacturer Part Number: MAX4215EUA+
• Description: IC BUFFER R-R W/ENABLE 8-UMAX
• Manufacturer: Maxim Integrated Products

Specifications of MAX4215EUA+

• Amplifier Type: Buffer
• Number Of Circuits: 1
• Output Type: Rail-to-Rail
• Slew Rate: 600 V/µs
• -3db Bandwidth: 230MHz
• Current - Input Bias: 5.4µA
• Voltage - Input Offset: 4000µV
• Current - Supply: 5.5mA
• Current - Output / Channel: 120mA
• Voltage - Supply, Single/dual (±): 3.15 V ~ 11 V, ±1.575 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Gain Bandwidth Product: -

Figure 5. Input Protection Circuit
Figure 7. Driving a Capacitive Load Through an Isolation
Resistor
Driving large capacitive loads increases the chance of
oscillations occurring in most amplifier circuits. This is
especially true for circuits with high loop gains, such as
voltage followers. The buffer’s output resistance and the
load capacitor combine to add a pole and excess phase
to the loop response. If the frequency of this pole is low
enough to interfere with the loop response and degrade
phase margin sufficiently, oscillations can occur.
A second problem when driving capacitive loads
results from the amplifier’s output impedance, which
looks inductive at high frequencies. This inductance
forms an L-C resonant circuit with the capacitive load,
which causes peaking in the frequency response and
degrades the amplifier’s gain margin.
IN+
IN-
V
IN
50
R
TIN
Closed-Loop, Rail-to-Rail Buffers with Enable
500
500
______________________________________________________________________________________
MAX42_ _
High-Speed, Single-Supply, Gain of 2,
500
500
MAX4214
MAX4215
MAX4217
MAX4219
MAX4222
R
ISO
C
V
L
OUT
OUT
Figure 6 shows the devices’ frequency response under
different capacitive loads. To drive loads with greater
than 20pF of capacitance or to settle out some of
the peaking, the output requires an isolation resistor
like the one shown in Figure 7. Figure 8 is a graph of
the Optimal Isolation Resistor vs. Load Capacitance.
Figure 9 shows the frequency response of the
MAX4214/MAX4215/MAX4217/MAX4219/MAX4222
when driving capacitive loads with a 27
resistor.
Coaxial cables and other transmission lines are easily
driven when properly terminated at both ends with their
characteristic impedance. Driving back-terminated
transmission lines essentially eliminates the lines’
capacitance.
Figure 6. Small-Signal Gain vs. Frequency with Load
Capacitance and No Isolation Resistor
Figure 8. Isolation Resistance vs. Capacitive Load
-1
-2
-3
-4
16
14
12
10
6
5
4
3
2
1
0
8
6
4
2
0
100k
0
50
1M
FREQUENCY (Hz)
100
C
C
L
LOAD
= 10pF
10M
(pF)
150
C
L
100M
= 5pF
200
C
L
= 15pF
250
1G
isolation
11