TL431CD ON Semiconductor, TL431CD Datasheet - Page 12

• Manufacturer Part Number: TL431CD
• Description: Voltage & Current References 2.5-36V ADJ 1-100mA
• Manufacturer: ON Semiconductor

Specifications of TL431CD

• Product: Voltage References
• Topology: Shunt References
• Output Voltage: Adjustable
• Initial Accuracy: 2.2 %
• Average Temperature Coefficient (typ): 50 PPM / C
• Series Vref - Input Voltage (max): 37 V
• Shunt Current (max): 100 mA
• Maximum Operating Temperature: + 70 C
• Package / Case: SOIC-8
• Minimum Operating Temperature: 0 C
• Mounting Style: SMD/SMT
• Shunt Current (min): 1 mA
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Example 2.
reference input pin. An examination of the data sheet
stability boundary curve (Figure 15) shows that this value of
load capacitance and cathode current is on the boundary.
Define the transfer gain.
The asymptotic plot may be expressed as the following
equation:
Av + 615
I
The DC gain is:
The resulting open loop Bode plot is shown in Figure 33.
Figure 32. Example 1 Circuit Open Loop Gain Plot
C
-10
-20
60
50
40
30
20
10
= 7.5 mA, R
0
(2.323)(1.0 M)(1.25 m)(2200) + 6389 + 76 dB
10
1
TL431 OPEN-LOOP VOLTAGE GAIN VERSUS FREQUENCY
Input
8.25 k
1 )
9.0 mF
10
2
L
G + G
8.0 kHz
= 2.2 kW, C
15 k
jf
10
3
f, FREQUENCY (Hz)
M
R
1
1 )
GM
1 )
L
10
GoR
= 0.01 mF. Cathode tied to
Ref
4
500 kHz
500 k
60 kHz
jf
jf
L
+
10
5
1.78 V
V
Figure 31. Simplified TL431 Device Model
1 )
ref
C
L
+
-
7.2 kHz
10
6
R
jf
http://onsemi.com
ref
16
10
7
G
12
M
formed by the load capacitance and load resistance.
250 kHz, having a phase margin of about −46 degrees.
Therefore, instability of this circuit is likely.
for stabilizing this circuit is to add a zero. However, that can
only be done by adding a series resistance to the output
capacitance, which will reduce its effectiveness as a noise
filter. Therefore, practically, in reference voltage
applications, the best solution appears to be to use a smaller
value of capacitance in low noise applications or a very
large value to provide noise filtering and a dominant pole
rolloff of the system.
Note that the transfer function now has an extra pole
Note that the crossover frequency in this case is about
With three poles, this system is unstable. The only hope
Figure 33. Example 2 Circuit Open Loop Gain Plot
-20
Anode
80
60
40
20
0
R
1.0 M
10
GM
V
1
CC
3
Cathode
2
R
L
TL431 OPEN-LOOP BODE PLOT WITH LOAD CAP
10
20 pF
C
2
P1
R
15.9 k
10 M
Z1
f, FREQUENCY (Hz)
R
P2
10
3
1.0 mmho
C
0.265 pF
P2
10
Go
4
10
5
10
6