Datasheet TL431IP, TL431ILPRP, TL431ILPRA, TL431ID, TL431ILP Datasheet (MOTOROLA)

Order this document by TL431/D

T

0° to +70°C

T

40° to +85°C

  


 

The TL431, A, B integrated circuits are three–terminal programmable
shunt regulator diodes. These monolithic IC voltage references operate as a
low temperature coefficient zener which is programmable from V
with two external resistors. These devices exhibit a wide operating current
range of 1.0 mA to 100 mA with a typical dynamic impedance of 0.22 Ω. The
characteristics of these references make them excellent replacements for
zener diodes in many applications such as digital voltmeters, power
supplies, and op amp circuitry. The 2.5 V reference makes it convenient to
obtain a stable reference from 5.0 V logic supplies, and since the TL431, A,
B operates as a shunt regulator, it can be used as either a positive or
negative voltage reference.

• Programmable Output Voltage to 36 V

• Voltage Reference Tolerance: ±0.4%, Typ @ 25°C (TL431B)

• Low Dynamic Output Impedance, 0.22 Ω Typical

• Sink Current Capability of 1.0 mA to 100 mA

• Equivalent Full–Range Temperature Coefficient of 50 ppm/°C Typical

• Temperature Compensated for Operation over Full Rated Operating

Temperature Range

• Low Output Noise Voltage

to 36 V

ref



PROGRAMMABLE

PRECISION REFERENCES

SEMICONDUCTOR

TECHNICAL DATA

LP SUFFIX

PLASTIC PACKAGE

CASE 29

(TO–92)

8

1

2

3

PLASTIC PACKAGE

1

Pin 1. Reference

2. Anode

3. Cathode

P SUFFIX

CASE 626

ORDERING INFORMATION

Operating

Device

TL431CLP, ACLP , BCLP
TL431CP, ACP, BCP
TL431CDM, ACDM, BCDM
TL431CD, ACD, BCD SOP–8
TL431ILP, AILP , BILP
TL431IP, AIP , BIP
TL431IDM, AIDM, BIDM
TL431ID, AID, BID SOP–8

Temperature Range

°

°

°

°

A

A

= –

=

–

Package

TO–92
Plastic

Micro–8

TO–92
Plastic

Micro–8

DM SUFFIX

8

1

Cathode

N/C
N/C
N/C

D SUFFIX

PLASTIC PACKAGE

CASE 751

(SOP–8)

Cathode

Anode Anode

N/C

SOP–8 is an internally modified SO–8 package. Pins 2,
3, 6 and 7 are electrically common to the die attach flag.
This internal lead frame modification decreases power
dissipation capability when appropriately mounted on a
printed circuit board. SOP–8 conforms to all external
dimensions of the standard SO–8 package.

PLASTIC PACKAGE

CASE 846A

(Micro–8)

1
2
3
4

(Top View)

1
2
3
4

8
7
6
5

8

8
7
6
5

(Top View)

Reference
N/C
Anode
N/C

1

Reference

N/C

MOTOROLA ANALOG IC DEVICE DATA

 Motorola, Inc. 1999 Rev 7

1

TL431, A, B Series

Symbol

Cathode

(K)

Reference

(R)

Anode

(A)

Reference

(R)

Representative Block Diagram

Reference

(R)

2.5 V

+
–

ref

Anode (A)

Cathode

(K)

2.4 k 7.2 k

This device contains 12 active transistors.

MAXIMUM RATINGS (Full operating ambient temperature range applies, unless

otherwise noted.)

Rating

Cathode to Anode Voltage V
Cathode Current Range, Continuous I
Reference Input Current Range, Continuous I
Operating Junction Temperature T
Operating Ambient Temperature Range T

TL431I, TL431AI, TL431BI –40 to +85
TL431C, TL431AC, TL431BC 0 to +70

Storage Temperature Range T
Total Power Dissipation @ TA = 25°C P

Derate above 25°C Ambient Temperature
D, LP Suffix Plastic Package 0.70
P Suffix Plastic Package 1.10
DM Suffix Plastic Package 0.52

Total Power Dissipation @ TC = 25°C P

Derate above 25°C Case Temperature
D, LP Suffix Plastic Package 1.5
P Suffix Plastic Package 3.0

NOTE: ESD data available upon request.

Symbol Value Unit

KA

K

ref

J

37 V

–100 to +150 mA

–0.05 to +10 mA

150 °C

A

stg

–65 to +150 °C

D

D

Representative Schematic Diagram

Component values are nominal

Cathode (K)

800

20 pF

150

10 k

1.0 k

3.28 k

°C

W

W

800

20 pF

800

4.0 k

Anode (A)

RECOMMENDED OPERATING CONDITIONS

Condition Symbol Min Max Unit

Cathode to Anode Voltage V
Cathode Current I

THERMAL CHARACTERISTICS

D, LP Suffix

Characteristic Symbol

Thermal Resistance, Junction–to–Ambient R
Thermal Resistance, Junction–to–Case R

θJA

θJC

Package

2

KA

K

V

ref

1.0 100 mA

P Suffix
Package

36 V

DM Suffix

Package

Unit

178 114 240 °C/W

83 41 – °C/W

MOTOROLA ANALOG IC DEVICE DATA

TL431, A, B Series

ref

D

V

ELECTRICAL CHARACTERISTICS (T

= 25°C, unless otherwise noted.)

A

TL431I TL431C

Characteristic Symbol

Reference Input Voltage (Figure 1) V

VKA = V

, IK = 10 mA

ref

ref

Min Typ Max Min Typ Max Unit

TA = 25°C 2.44 2.495 2.55 2.44 2.495 2.55
TA = T

Reference Input Voltage Deviation Over ∆V

low

to T

(Note 1) 2.41 – 2.58 2.423 – 2.567

high

ref

– 7.0 30 – 3.0 17 mV

Temperature Range (Figure 1, Notes 1, 2)

VKA= V

Ratio of Change in Reference Input Voltage

to Change in Cathode to Anode Voltage

IK = 10 mA (Figure 2),

∆VKA = 10 V to V

ref, IK

= 10 mA

ref

D

V

D

V

KA

– –1.4 –2.7 – –1.4 –2.7

∆VKA = 36 V to 10 V – –1.0 –2.0 – –1.0 –2.0

Reference Input Current (Figure 2) I

ref

IK = 10 mA, R1 = 10 k, R2 = ∞

TA = 25°C – 1.8 4.0 – 1.8 4.0
TA = T

Reference Input Current Deviation Over ∆I

low

to T

(Note 1) – – 6.5 – – 5.2

high

ref

– 0.8 2.5 – 0.4 1.2 µA

Temperature Range (Figure 2, Note 1, 4)

IK = 10 mA, R1 = 10 k, R2 = ∞

Minimum Cathode Current For Regulation I

VKA = V

(Figure 1)

ref

Off–State Cathode Current (Figure 3) I

VKA = 36 V, V

ref

= 0 V

min

off

– 0.5 1.0 – 0.5 1.0 mA

– 260 1000 – 260 1000 nA

Dynamic Impedance (Figure 1, Note 3) |ZKA| – 0.22 0.5 – 0.22 0.5 Ω

VKA = V

, ∆IK = 1.0 mA to 100 mA

ref

f ≤ 1.0 kHz

NOTES: 1. T

= –40°C for TL431AIP TL431AILP, TL431IP, TL431ILP, TL431BID, TL431BIP, TL431BILP, TL431AIDM, TL431IDM, TL431BIDM

low

=0°C for TL431ACP, TL431ACLP, TL431CP , TL431CLP, TL431CD, TL431ACD, TL431BCD, TL431BCP , TL431BCLP, TL431CDM,

TL431ACDM, TL431BCDM

T

= +85°C for TL431AIP, TL431AILP, TL431IP, TL431ILP, TL431BID, TL431BIP, TL431BILP, TL431IDM, TL431AIDM, TL431BIDM

high

= +70°C for TL431ACP, TL431ACLP, TL431CP, TL431ACD, TL431BCD, TL431BCP, TL431BCLP , TL431CDM, TL431ACDM, TL431BCDM

2.The deviation parameter ∆V
temperature range that applies.

is defined as the difference between the maximum and minimum values obtained over the full operating ambient

ref

V

mV/V

µA

The average temperature coefficient of the reference input voltage, αV

V

ref

αV

can be positive or negative depending on whether V

ref

3.The dynamic impedance ZKA is defined as
When the device is programmed with two external resistors, R1 and R2, (refer to Figure 2) the total dynamic impedance of the circuit is defined as:

Example :DV

+

8.0 mV and slope is positive,

ref

V

@25_C+2.495 V,DTA+70_

ref

MOTOROLA ANALOG IC DEVICE DATA

V

ref

V

ref

ppm

_

|ZKA|

C

max

min

+

T1

ǒ

V

D

+

Ambient T emperature

ref

D

V

ref

X10

Ǔ

@25_C

ref

D

T

A

Min or V

ref

V

KA

D

I

K

|ZKAȀ|[

ref

C

|ZKA|ǒ1

∆

V

= V

max

ref

ref

–V

min

ref

∆

TA = T2 – T

1

T2

is defined as:

6

Max occurs at the lower ambient temperature. (Refer to Figure 6.)

D

V

R1
R2

D

ref

V

TA(V

0.008 x 10

+

70 (2.495)

Ǔ

+

a

)

ref

ref

6

x10

@25_C)

6

+

45.8 ppmń_

C

3

TL431, A, B Series

ref

D

V

ELECTRICAL CHARACTERISTICS (T

= 25°C, unless otherwise noted.)

A

TL431AI TL431AC TL431BI

Characteristic Symbol

Reference Input Voltage (Figure 1) V

VKA = V

, IK = 10 mA

ref

Min Typ Max Min Typ Max Min Typ Max Unit

ref

TA = 25°C 2.47 2.495 2.52 2.47 2.495 2.52 2.483 2.495 2.507
TA = T

Reference Input Voltage Deviation Over ∆V

low

to T

high

2.44 – 2.55 2.453 – 2.537 2.475 2.495 2.515
– 7.0 30 – 3.0 17 – 3.0 17 mV

ref

Temperature Range (Figure 1, Notes 1, 2)

VKA= V

Ratio of Change in Reference Input Voltage

to Change in Cathode to Anode Voltage

IK = 10 mA (Figure 2),

∆VKA = 10 V to V

ref, IK

= 10 mA

ref

D

V

D

V

KA

– –1.4 –2.7 – –1.4 –2.7 – –1.4 –2.7

∆VKA = 36 V to 10 V – –1.0 –2.0 – –1.0 –2.0 – –1.0 –2.0

Reference Input Current (Figure 2) I

ref

IK = 10 mA, R1 = 10 k, R2 = ∞

TA = 25°C – 1.8 4.0 – 1.8 4.0 – 1.1 2.0
TA = T

Reference Input Current Deviation Over ∆I

low

to T

(Note 1) – – 6.5 – – 5.2 – – 4.0

high

ref

– 0.8 2.5 – 0.4 1.2 – 0.8 2.5 µA

Temperature Range (Figure 2, Note 1)

IK = 10 mA, R1 = 10 k, R2 = ∞

Minimum Cathode Current For Regulation I

VKA = V

(Figure 1)

ref

Off–State Cathode Current (Figure 3) I

VKA = 36 V, V

ref

= 0 V

min

off

– 0.5 1.0 – 0.5 1.0 – 0.5 1.0 mA

– 260 1000 – 260 1000 – 230 500 nA

Dynamic Impedance (Figure 1, Note 3) |ZKA| – 0.22 0.5 – 0.22 0.5 – 0.14 0.3 Ω

VKA = V

, ∆IK = 1.0 mA to 100 mA

ref

f ≤ 1.0 kHz

NOTES: 1. T

= –40°C for TL431AIP TL431AILP, TL431IP, TL431ILP, TL431BID, TL431BIP, TL431BILP, TL431AIDM, TL431IDM, TL431BIDM

low

=0°C for TL431ACP, TL431ACLP, TL431CP , TL431CLP, TL431CD, TL431ACD, TL431BCD, TL431BCP , TL431BCLP, TL431CDM,

TL431ACDM, TL431BCDM

T

= +85°C for TL431AIP, TL431AILP, TL431IP, TL431ILP, TL431BID, TL431BIP, TL431BILP, TL431IDM, TL431AIDM, TL431BIDM

high

= +70°C for TL431ACP, TL431ACLP, TL431CP, TL431ACD, TL431BCD, TL431BCP, TL431BCLP , TL431CDM, TL431ACDM, TL431BCDM

2.The deviation parameter ∆V
temperature range that applies.

is defined as the difference between the maximum and minimum values obtained over the full operating ambient

ref

V

max

ref

V

min

ref

∆

V

= V

ref

–V

min

ref

∆

TA = T2 – T

ref

max

1

V

mV/V

µA

T1

Ambient T emperature

The average temperature coefficient of the reference input voltage, αV

D

V

ref

ǒ

V

ppm

V

ref

_

C

αV

can be positive or negative depending on whether V

ref

3.The dynamic impedance ZKA is defined as
When the device is programmed with two external resistors, R1 and R2, (refer to Figure 2) the total dynamic impedance of the circuit is defined as:

Example :DV

+

8.0 mV and slope is positive,

ref

V

@25_C+2.495 V,DTA+70_

ref

|ZKA|

ref

+

D

V

+

D

|ZKAȀ|[

@25_C

D

Min or V

ref

KA

I

K

Ǔ

T

A

C

|ZKA|ǒ1

4

T2

is defined as:

ref

6

X10

Max occurs at the lower ambient temperature. (Refer to Figure 6.)

ref

D

V

R1
R2

D

ref

V

TA(V

0.008 x 10

+

70 (2.495)

Ǔ

+

a

)

ref

ref

6

x10

@25_C)

6

+

45.8 ppmń_

C

MOTOROLA ANALOG IC DEVICE DATA

TL431, A, B Series

0

5

Figure 1. Test Circuit for VKA = V

Input

V

ref

V

KA

I

K

Figure 4. Cathode Current versus

Cathode Voltage

ref

°

C

KA

I

K

, CATHODE CURRENT (mA)

K

I

150

100

Input V

50

0

–50

VKA = V
TA = 25

ref

Figure 2. Test Circuit for VKA > V

I

K

VKA+

V

KA

R1

ǒ

V

1

)

ref

R2

Input

R1

R2

I

ref

V

ref

Figure 5. Cathode Current versus

800

600

Input

µ

400

200

, CATHODE CURRENT ( A)

0

K

I

ref

Ǔ

)

I

ref

VKA = V
TA = 25

Figure 3. T est Circuit for I

S

R1

Cathode Voltage

ref

°

C

V

KA

I

K

Input V

I

I

off

Min

off

KA

–100

–2.0 –1.0 0

Figure 6. Reference Input V oltage versus

2600

Input

2580
2560
2540
2520
2500
2480

2460
2440
2420

ref

V , REFERENCE INPUT VOLTAGE (mV)

2400

–55

V

ref

TA, AMBIENT TEMPERATURE (

1.0 2.0 3.0

VKA, CATHODE VOLTAGE (V)

Ambient Temperature

V

KA

I

VKA = V

K

ref

IK = 10 mA

050

25–25

V

Max = 2550 mV

ref

V

Typ = 2495 mV

ref

V

Min = 2440 mV

ref

75 100 125

°

C)

–200

µ

, REFERENCE INPUT CURRENT ( A)

ref

I

–1.0

0

1.0 2.0 3.

VKA, CATHODE VOLTAGE (V)

Figure 7. Reference Input Current versus

Ambient Temperature

3.0

2.5

2.0

1.5
IK = 10 mA

1.0

0.5

Input

I

ref

10k

0

V

KA

I

K

250–25

TA, AMBIENT TEMPERATURE (°C)

12

10050 75–55

MOTOROLA ANALOG IC DEVICE DATA

5

TL431, A, B Series

0

–8.0

–16

–24

, REFERENCE INPUT VOLTAGE (mV)

ref

V

∆

–32

100

Ω

10

Figure 8. Change in Reference Input

V oltage versus Cathode Voltage

Input V

R1

R2

V

ref

KA

I

K

20

VKA, CATHODE VOLTAGE (V)

Figure 10. Dynamic Impedance

versus Frequency

1.0 k
50

Output

I

K

–
+

Gnd

TA = 25_C

∆

IK = 1.0 mA to 100 mA

IK = 10 mA
TA = 25

30100

Figure 9. Off–State Cathode Current

versus Ambient T emperature

1.0 k

°

C

40

, OFF–STATE CATHODE CURRENT (nA)

off

I

100

10

1.0

0.1

0.01
–55

Input

75–25 0 25 50 100 125

TA, AMBIENT TEMPERATURE (5C)

VKA = 36 V
V

= 0 V

ref

I

off

V

KA

Figure 11. Dynamic Impedance

versus Ambient T emperature

0.320
VKA = V

Ω

0.300

0.280

0.260

ref

∆

IK = 1.0 mA to 100 mA

≤

1.0 kHz

f

1.0 k
50

Output

I

K

–
+

Gnd

1.0

|, DYNAMIC IMPEDANCE ( )

KA

|Z

0.1

Figure 12. Open–Loop V oltage Gain

60
50
40
30
20

IK = 10 mA

10

, OPEN LOOP VOL TAGE GAIN (dB)
A

TA = 25

0

VOL

–10

1.0 k 10 k

0.240

|, DYNAMIC IMPEDANCE ( )

KA

0.220

|Z

100 k 10 M1.0 M1.0 k 10 k

f, FREQUENCY (MHz)

0.200

–55

75–25 0 25 50 100 125

TA, AMBIENT TEMPERATURE (

_

C)

Figure 13. Spectral Noise Density

versus Frequency

Output

I

K

15 k

9.0

µ

F

8.25 k

_

C

100 k

f, FREQUENCY (MHz)

230

Gnd

10 M1.0 M

80

60

√

40

20

NOISE VOLTAGE (nV/ Hz)

0

10 10 k1.0 k100

VKA = V
IK = 10 mA
TA = 25°C

Input

f, FREQUENCY (Hz)

ref

I

K

Output

100 k

6

MOTOROLA ANALOG IC DEVICE DATA

TL431, A, B Series

Figure 14. Pulse Response Figure 15. Stability Boundary Conditions

TA = 25_C

3.0

2.0

1.0

0

VOLTAGE SWING (V)

5.0
0

0 8.04.0 20

Output

Input

t, TIME (

µ

s)

Input

Monitor

Pulse

Generator

f = 100 kHz

12

16

Figure 16. Test Circuit For Curve A

of Stability Boundary Conditions

150

I

K

V+

C

L

220

50

Output

Gnd

140

A) VKA = V
B) VKA = 5.0 V @ IK = 10 mA

120

C) VKA = 10 V @ IK = 10 mA
D) VKA = 15 V @ IK = 10 mA

100

D) TA = 25

80

60
40

, CATHODE CURRENT (mA)

K

I

20

0

100 pF

ref

°

C

Stable

1000 pF 0.01

CL, LOAD CAPACITANCE

A

B

C

D

µ

F 0.1 µF 1.0 µF 10 µF

Figure 17. Test Circuit For Curves B, C, And D

of Stability Boundary Conditions

150

I

K

V+

10 k

Stable

A

B

C

L

Figure 18. Shunt Regulator Figure 19. High Current Shunt Regulator

V+

R1

R2

R1

+ǒ1

V

out

Ǔ

)

V

ref

R2

MOTOROLA ANALOG IC DEVICE DATA

TYPICAL APPLICATIONS

V

out

V+ V

R1

R2

R1

V

+ǒ1

out

Ǔ

)

V

ref

R2

out

7

TL431, A, B Series

Figure 20. Output Control for a

Figure 21. Series Pass Regulator

Three–T erminal Fixed Regulator

V+

MC7805

V+ V

In

V

out

V

out

Out

Common

+ǒ1

)

min

+

out

R1

R2

R1

+ǒ1

V

R1

Ǔ

V

ref

R2

V

)

5.0V

ref

out

V

min

out

Ǔ

)

V

ref

R2

+

V

)

V

ref

be

Figure 22. Constant Current Source Figure 23. Constant Current Sink

R

V+

I

out

CL

V

ref

+

R

CL

I

out

V+

I

sink

I

Sink

R

S

+

R1

R2

V

out

V

ref

R

S

Figure 24. TRIAC Crowbar Figure 25. SRC Crowbar

R1

R2

V

ref

V

out

V+

V

out(trip)

+ǒ1

R1

Ǔ

)

R2

R1

R2

V

ref

V

out

8

V+

R1

V

out(trip)

+ǒ1

Ǔ

)

R2

MOTOROLA ANALOG IC DEVICE DATA

TL431, A, B Series

Figure 26. V oltage Monitor Figure 27. Single–Supply Comparator with

T emperature–Compensated Threshold

V+

l

L.E.D. indicator is ‘on’ when V+ is between the
upper and lower limits.

Lower Limit

Upper Limit

+ǒ1

+ǒ1

)

)

R1 R3

R2 R4

R1

Ǔ

V

ref

R2
R3

Ǔ

V

ref

R4

V

out

V

in

Vth = V

ref

V+

V

out

V

< V
> V

Figure 28. Linear Ohmmeter Figure 29. Simple 400 mW Phono Amplifier

1N5305

25 V

2.0 mA

Tl = 330 to 8.0

Ω

38 V

330

V

in

out

V+

ref

≈ 2.0 V

ref

5.0 k
1%

1.0 k
V

50 k

1%

10 k

Ω

5.0 M

500 k

Ω

V

R

1%

X

100 k

V
Range

1%

Ω

Ω

1.0 M
V

+

R

x

W

V

D

out

V

Calibrate

25 V

–
LM11
+

–5.0 V

Range

10 k

8.0

Ω

V

out

*Thermalloy

*THM 6024
*Heatsink on
*LP Package

T

I

360 k

*

56 k 10 k 25 k

1.0

+

µ

F

470

µ

F

Volume

µ

F

0.05

Tone

47 k

MOTOROLA ANALOG IC DEVICE DATA

9

TL431, A, B Series

Figure 30. High Efficiency Step–Down Switching Converter

Vin = 10 V to 20 V

+

Line Regulation Vin = 10 V to 20 V, Io = 1.0 A 53 mV (1.1%)
Load Regulation Vin = 15 V, Io = 0 A to 1.0 A 25 mV (0.5%)
Output Ripple Vin = 10 V, Io = 1.0 A 50 mVpp P .A.R.D.
Output Ripple Vin = 20 V, Io = 1.0 A 100 mVpp P .A.R.D.
Efficiency Vin = 15 V, Io = 1.0 A 82%

150 mH @ 2.0 A

TIP115

1.0 k

4.7 k

MPSA20

µ

F

2200

Test Conditions Results

0.1

4.7 k

µ

F

102.2 k

4.7 k

1N5823

0.01

µ

F

100 k

470

51 k

V

= 5.0 V

out

I

= 1.0 A

out

+

µ

F

10

MOTOROLA ANALOG IC DEVICE DATA

TL431, A, B Series

APPLICATIONS INFORMATION

The TL431 is a programmable precision reference which
is used in a variety of ways. It serves as a reference voltage
in circuits where a non–standard reference voltage is
needed. Other uses include feedback control for driving an
optocoupler in power supplies, voltage monitor, constant
current source, constant current sink and series pass
regulator. In each of these applications, it is critical to
maintain stability of the device at various operating currents
and load capacitances. In some cases the circuit designer
can estimate the stabilization capacitance from the stability
boundary conditions curve provided in Figure 15. However,
these typical curves only provide stability information at
specific cathode voltages and at a specific load condition.
Additional information is needed to determine the
capacitance needed to optimize phase margin or allow for
process variation.

A simplified model of the TL431 is shown in Figure 31.
When tested for stability boundaries, the load resistance is
150 W. The model reference input consists of an input
transistor and a dc emitter resistance connected to the
device anode. A dependent current source, Gm, develops a
current whose amplidute is determined by the difference
between the 1.78 V internal reference voltage source and the
input transistor emitter voltage. A portion of Gm flows through
compensation capacitance, CP2. The voltage across C
drives the output dependent current source, Go, which is
connected across the device cathode and anode.

Model component values are:

V

= 1.78 V

ref

Gm = 0.3 + 2.7 exp (–IC/26 mA)
where IC is the device cathode current and Gm is in mhos

Go = 1.25 (Vcp2) µmhos.

Resistor and capacitor typical values are shown on the
model. Process tolerances are ±20% for resistors, ±10% for
capacitors, and ±40% for transconductances.

An examination of the device model reveals the location of
circuit poles and zeroes:

P1

+

2pRGMC

1

+

2p* 1.0 M * 20 pF

P1

1

+

7.96 kHz

P2

P2

+

Z1

+

In addition, there is an external circuit pole defined by the

load:

Also, the transfer dc voltage gain of the TL431 is:

Example 1:
IC+

10 mA,RL+

The DC gain is:

Loop gain+G

The resulting transfer function Bode plot is shown in
Figure 32. The asymptotic plot may be expressed as the
following equation:

The Bode plot shows a unity gain crossover frequency of
approximately 600 kHz. The phase margin, calculated from
the equation, would be 55.9 degrees. This model matches
the Open–Loop Bode Plot of Figure 12. The total loop would
have a unity gain frequency of about 300 kHz with a phase
margin of about 44 degrees.

1

2pRP2C

2pRZ1C

(2.138)(1.0 M)(1.25m)(230)+615+56 dB

+

2p* 10 M * 0.265 pF

P2

1

+

2p*15.9k*20pF

P1

PL+

G+GMRGMGoR

230W,CL+

G+GMRGMGoRL+

8.25 k

8.25 k)15 k

Av+615

ǒ

8.0 kHz

1

1

1

2pRLC

1)jf

L

L

0. Define the transfer gain.

+

1)jf

ǒ

500 kHz

1)jf

Ǔǒ

60 kHz

+

60 kHz

+

500 kHz

218+47 dB

Ǔ

Ǔ

MOTOROLA ANALOG IC DEVICE DATA

11

Input

8.25 k

9.0

TL431, A, B Series

Figure 31. Simplified TL431 Device Model

V

CC

R

L

C

L

R

GM

1.0 M

Anode 2

3
Cathode

20 pF

R

P2

10 M

C

P1

R

Z1

15.9 k

m

mho

1.0

C

P2

0.265 pF

Go

15 k

m

F

Ref

1

500 k

V

ref

1.78 V

G

+

R

ref

–

16

M

Figure 32. Example 1

Circuit Open Loop Gain Plot

TL431 OPEN–LOOP VOLTAGE GAIN VERSUS FREQUENCY

60
50
40

30
20

10

0

–10

Av, OPEN–LOOP VOLT AGE GAIN (dB)

–20

10

2

1

10

3

10

f, FREQUENCY (Hz)

10

4

10

5

10

6

10

Example 2.

IC = 7.5 mA, RL = 2.2 kW, CL = 0.01 mF. Cathode tied to
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 DC gain is:

G+GMRGMGoRL+

(2.323)(1.0 M)(1.25m)(2200)+6389+76 dB

The resulting open loop Bode plot is shown in Figure 33.
The asymptotic plot may be expressed as the following
equation:

1)jf

Av+615

1)jf

ǒ

8.0 kHz

ǒ

500 kHz

Ǔǒ

60 kHz

1)jf

Ǔ

Ǔǒ

7.2 kHz

1)jf

Ǔ

Note that the transfer function now has an extra pole

formed by the load capacitance and load resistance.

Note that the crossover frequency in this case is about
250 kHz, having a phase margin of about –46 degrees.
Therefore, instability of this circuit is likely.

Figure 33. Example 2

Circuit Open Loop Gain Plot

80

60

40

7

20

Av, OPEN–LOOP GAIN (dB)

0

–20

TL431 OPEN–LOOP BODE PLOT WITH LOAD CAP

10

1

10

2

3

10

f, FREQUENCY (Hz)

10

4

With three poles, this system is unstable. The only hope
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.

10

5

10

6

12

MOTOROLA ANALOG IC DEVICE DATA

SEATING
PLANE

TL431, A, B Series

OUTLINE DIMENSIONS

LP SUFFIX

PLASTIC PACKAGE

CASE 29–04

A

B

(TO–92)

ISSUE AE

R

P

L

XX

V

1

F

G

H

K

D

J

C

SECTION X–X

N

N

NOTES:

1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.

2. CONTROLLING DIMENSION: INCH.

3. CONTOUR OF PACKAGE BEYOND DIMENSION R
IS UNCONTROLLED.

4. DIMENSION F APPLIES BETWEEN P AND L.
DIMENSION D AND J APPLY BETWEEN L AND K
MINIMUM. LEAD DIMENSION IS UNCONTROLLED
IN P AND BEYOND DIMENSION K MINIMUM.

DIM MIN MAX MIN MAX

A 0.175 0.205 4.45 5.20
B 0.170 0.210 4.32 5.33
C 0.125 0.165 3.18 4.19
D 0.016 0.022 0.41 0.55
F 0.016 0.019 0.41 0.48
G 0.045 0.055 1.15 1.39
H 0.095 0.105 2.42 2.66
J 0.015 0.020 0.39 0.50
K 0.500 ––– 12.70 –––
L 0.250 ––– 6.35 –––
N 0.080 0.105 2.04 2.66
P ––– 0.100 ––– 2.54
R 0.115 ––– 2.93 –––
V 0.135 ––– 3.43 –––

MILLIMETERSINCHES

NOTE 2

–T–

SEATING
PLANE

H

58

–B–

14

F

–A–

C

N

D

K

G

0.13 (0.005) B

M

T

P SUFFIX

PLASTIC PACKAGE

CASE 626–05

ISSUE K

L

J

M

M

A

M

NOTES:

1. DIMENSION L TO CENTER OF LEAD WHEN
FORMED PARALLEL.

2. PACKAGE CONTOUR OPTIONAL (ROUND OR
SQUARE CORNERS).

3. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.

DIM MIN MAX MIN MAX

A 9.40 10.16 0.370 0.400
B 6.10 6.60 0.240 0.260
C 3.94 4.45 0.155 0.175
D 0.38 0.51 0.015 0.020
F 1.02 1.78 0.040 0.070

G 2.54 BSC 0.100 BSC

H 0.76 1.27 0.030 0.050
J 0.20 0.30 0.008 0.012
K 2.92 3.43 0.115 0.135
L 7.62 BSC 0.300 BSC

M ––– 10 ––– 10

N 0.76 1.01 0.030 0.040

INCHESMILLIMETERS

__

MOTOROLA ANALOG IC DEVICE DATA

13

PIN 1 ID

SEATING
PLANE

–T–

0.038 (0.0015)

TL431, A, B Series

OUTLINE DIMENSIONS

DM SUFFIX

PLASTIC PACKAGE

CASE 846A–02

–A–

K

G

–B–

D

8 PL

0.08 (0.003) A

(Micro–8)

ISSUE D

M

T

S

B

S

C

NOTES:

6. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.

7. CONTROLLING DIMENSION: MILLIMETER.

8. DIMENSION A DOES NOT INCLUDE MOLD FLASH,
PROTRUSIONS OR GATE BURRS. MOLD FLASH,
PROTRUSIONS OR GATE BURRS SHALL NOT
EXCEED 0.15 (0.006) PER SIDE.

9. DIMENSION B DOES NOT INCLUDE INTERLEAD
FLASH OR PROTRUSION. INTERLEAD FLASH OR
PROTRUSION SHALL NOT EXCEED 0.25 (0.010)
PER SIDE.

DIM MIN MAX MIN MAX

A 2.90 3.10 0.114 0.122
B 2.90 3.10 0.114 0.122
C ––– 1.10 ––– 0.043
D 0.25 0.40 0.010 0.016

G 0.65 BSC 0.026 BSC

H 0.05 0.15 0.002 0.006
J 0.13 0.23 0.005 0.009
K 4.75 5.05 0.187 0.199
L 0.40 0.70 0.016 0.028

INCHESMILLIMETERS

A

C

A1

H

J

L

D SUFFIX

PLASTIC PACKAGE

CASE 751–06

(SOP–8)
ISSUE T

D

58

0.25MB

E

1

B

e

H

4

M

h

X 45

_

q

C

A

SEATING
PLANE

0.10

L

B

SS

A0.25MCB

NOTES:

1. DIMENSIONING AND TOLERANCING PER ASME
Y14.5M, 1994.

2. DIMENSIONS ARE IN MILLIMETER.

3. DIMENSION D AND E DO NOT INCLUDE MOLD
PROTRUSION.

4. MAXIMUM MOLD PROTRUSION 0.15 PER SIDE.

5. DIMENSION B DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOWABLE DAMBAR
PROTRUSION SHALL BE 0.127 TOTAL IN EXCESS
OF THE B DIMENSION AT MAXIMUM MATERIAL
CONDITION.

MILLIMETERS

DIM MIN MAX

A 1.35 1.75

A1 0.10 0.25

B 0.35 0.49
C 0.19 0.25
D 4.80 5.00
E

3.80 4.00

1.27 BSCe

H 5.80 6.20
h

0.25 0.50

L 0.40 1.25

0 7

q

__

14

MOTOROLA ANALOG IC DEVICE DATA

TL431, A, B Series

Motorola reserves the right to make changes without further notice to any products herein. Motorola makes no warranty , representation or guarantee regarding
the suitability of its products for any particular purpose, nor does Motorola assume any liability arising out of the application or use of any product or circuit, and
specifically disclaims any and all liability, including without limitation consequential or incidental damages. “T ypical” parameters which may be provided in Motorola
data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals”
must be validated for each customer application by customer’s technical experts. Motorola does not convey any license under its patent rights nor the rights of
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applications intended to support or sustain life, or for any other application in which the failure of the Motorola product could create a situation where personal injury
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and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees
arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that
Motorola was negligent regarding the design or manufacture of the part. Motorola and are registered trademarks of Motorola, Inc. Motorola, Inc. is an Equal
Opportunity/Affirmative Action Employer.

MOTOROLA ANALOG IC DEVICE DATA

15

TL431, A, B Series

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MOTOROLA ANALOG IC DEVICE DATA

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TL431/D