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ATL431, ATL432
SLVSCV5D – MARCH 2015 – REVISED OCTOBER 2016
ATL431, ATL432 2.5-V Low Iq Adjustable Precision Shunt Regulator
1 Features
3 Description
•
•
The ATL431 and ATL432 are three-terminal
adjustable shunt regulators, with specified thermal
stability over applicable automotive, commercial, and
industrial temperature ranges. The output voltage can
be set to any value between Vref (approximately
2.5 V) and 36 V, with two external resistors. These
devices have a typical output impedance of 0.05 Ω.
Active output circuitry provides a very sharp turn-on
characteristic, making these devices excellent
replacements for Zener diodes in many applications,
such as onboard regulation, adjustable power
supplies, and switching power supplies.
1
•
•
•
•
•
Adjustable Regulated Output of 2.5 V to 36 V
Very-Low Operating Current
– IKA(min) = 35 µA (Max)
– IREF = 150 nA (Max)
Internally Compensated for Stability
– Stable With No Capacitive Load
Reference Voltage Tolerances at 25°C
– 0.5% for B Grade
– 1% for A Grade
Typical Temperature Drift
– 5 mV (–40°C to +85°C); I Version
– 6 mV (–40°C to +125°C); Q Version
Extended Cathode Current Range
35 µA to 100 mA
Low Output Impedance of 0.3 Ω (Max)
2 Applications
•
•
•
•
•
•
Secondary Side Regulation in Flyback SMPSs
Industrial, Computing, Consumer, and Portables
Adjustable Voltage and Current Referencing
Power Management
Power Isolation
Zener Replacement
The ATL43x has > 20x improvement cathode current
range over it's TL43x predecessor. It also is stable
with a wider range of load capacitance types and
values.
ATL431 and ATL432 are the exact same parts but
with different pinouts and order numbers. The
ATL43x is offered in two grades, with initial
tolerances (at 25°C) of 0.5%, 1%, for the B and A
grade, respectively. In addition, low output drift vs
temperature ensures consistent voltage regulation
over the entire temperature range.
The ATL43xxI devices are characterized for operation
from –40°C to +85°C, and the ATL43xxQ devices are
characterized for operation from –40°C to +125°C.
Device Information(1)
PART NUMBER
ATL431
ATL432
PACKAGE
SOT (3)
BODY SIZE (NOM)
2.90 mm × 1.60 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Simplified Schematic
Stability Region for VKA = 15.0 V
2000
VKA
Input
IKA
IKA(PA)
Vref
1000
STABLE
100
20
0.0001
0.001
0.01
0.1
CKA(PF)
1
10
D001
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
ATL431, ATL432
SLVSCV5D – MARCH 2015 – REVISED OCTOBER 2016
www.ti.com
Table of Contents
1
2
3
4
5
6
7
8
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
3
6.1
6.2
6.3
6.4
6.5
6.6
6.7
3
3
3
4
4
4
5
Absolute Maximum Ratings .....................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics, ATL431Ax, ATL432Ax .....
Electrical Characteristics, ATL431Bx, ATL432Bx .....
Typical Characteristics ..............................................
Parameter Measurement Information .................. 9
Detailed Description ............................................ 11
8.1 Overview ................................................................. 11
8.2 Functional Block Diagram ....................................... 11
8.3 Feature Description................................................. 11
8.4 Device Functional Modes........................................ 12
9
Application and Implementation ........................ 13
9.1 Application Information............................................ 13
9.2 Typical Applications ................................................ 14
10 Power Supply Recommendations ..................... 18
11 Layout................................................................... 18
11.1 Layout Guidelines ................................................. 18
11.2 Layout Example .................................................... 18
12 Device and Documentation Support ................. 19
12.1
12.2
12.3
12.4
12.5
12.6
Related Links ........................................................
Receiving Notification of Documentation Updates
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
19
19
19
19
19
19
13 Mechanical, Packaging, and Orderable
Information ........................................................... 19
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision C (September 2015) to Revision D
Page
•
Changed Small-Signal Voltage Amplification vs Frequency with an updated graph to provide additional data .................... 6
•
Changed Test Circuit for Phase and Gain Measurement with an updated schematic........................................................... 9
•
Updated Comparator Mode specifications in Design Parameters........................................................................................ 14
•
Added Receiving Notification of Documentation Updates section ....................................................................................... 19
Changes from Revision B (May 2015) to Revision C
•
Page
Changed ATL432xx status from PREVIEW to PRODUCTION. ............................................................................................. 1
Changes from Revision A (April 2015) to Revision B
Page
•
Changed ATL431AQ, ATL431BI and ATL431BQ status from PREVIEW to PRODUCTION. ............................................... 1
•
Changed flyback schematic to represent a more robust design ......................................................................................... 13
•
Added flyback supply reliability recommendation................................................................................................................. 18
Changes from Original (March 2013) to Revision A
•
2
Page
Initial release of full verison. ................................................................................................................................................... 1
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5 Pin Configuration and Functions
ATL431 DBZ Package
3-Pin SOT-23
Top View
CATHODE
ATL432 DBZ Package
3-Pin SOT-23
Top View
1
REF
3
REF
1
ANODE
3
2
CATHODE
ANODE
2
Not to scale
Not to scale
Pin Functions
PIN
NO.
NAME
I/O
DESCRIPTION
ATL431x
ATL432x
CATHODE
1
2
I/O
REF
2
1
I
Threshold relative to common anode
ANODE
3
3
O
Common pin, normally connected to ground
Shunt Current/Voltage input
6 Specifications
6.1 Absolute Maximum Ratings (1)
over operating free-air temperature range (unless otherwise noted)
MIN
MAX
40
V
150
mA
(2)
UNIT
VKA
Cathode voltage
IKA
Continuous cathode current
–100
II(ref)
Reference input current
–0.05
10
mA
TJ
Operating virtual junction temperature
–40
150
°C
Tstg
Storage temperature
–65
150
°C
(1)
(2)
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating
Conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
All voltage values are with respect to ANODE, unless otherwise noted.
6.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
±2000
Charged-device model (CDM), per JEDEC specification JESD22-C101 (2)
±1000
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
6.3 Recommended Operating Conditions
MIN
MAX
VKA
Cathode voltage
Vref
36
V
IKA
Cathode current
.035
100
mA
TA
Operating free-air temperature
"I" Grade
–40
85
"Q" Grade
–40
125
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UNIT
°C
3
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SLVSCV5D – MARCH 2015 – REVISED OCTOBER 2016
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6.4 Thermal Information
ATL43xx
THERMAL METRIC (1)
DBZ (SOT-23)
UNIT
3 PINS
RθJA
Junction-to-ambient thermal resistance
331.8
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
106.5
°C/W
RθJB
Junction-to-board thermal resistance
64.6
°C/W
ψJT
Junction-to-top characterization parameter
4.9
°C/W
ψJB
Junction-to-board characterization parameter
62.9
°C/W
(1)
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report.
6.5 Electrical Characteristics, ATL431Ax, ATL432Ax
over recommended operating conditions, TA = 25°C (unless otherwise noted)
PARAMETER
Vref
Reference voltage
TEST CIRCUIT
Figure 22
TEST CONDITIONS
MIN
TYP
MAX
UNIT
2475
2500
2525
mV
ATL43xAI; TA =
-40°C to 85°C
5
15
ATL43xAQ; TA =
-40°C to 125°C
6
34
ΔVKA = 10 V − Vref
–0.4
–2.7
ΔVKA = 36 V − 10 V
–0.1
–2
VKA = Vref, IKA = 1 mA
Deviation of reference input
voltage over full temperature
range, see section
Figure 22
Ratio of change in reference
ΔVref / ΔVKA voltage to the change in
cathode voltage
Figure 23
IKA = 1 mA
Iref
Reference input current
Figure 23
IKA = 1 mA, R1 = 10 kΩ, R2 = ∞
30
150
nA
II(dev)
Deviation of reference input
current over full temperature
range, see section
Figure 23
IKA = 1 mA, R1 = 10 kΩ, R2 = ∞
20
50
nA
Imin
Minimum cathode current for
regulation
Figure 22
Figure 5
VKA = Vref
20
35
µA
Ioff
Off-state cathode current
Figure 24
VKA = 36 V, Vref = 0
0.05
0.2
µA
|zKA|
Dynamic impedance, see
section
Figure 22
VKA = Vref, f ≤ 1 kHz,
IKA = 1 mA to 100 mA
0.05
0.3
Ω
VI(dev)
VKA = Vref,
IKA = 1 mA,
mV
mV/V
6.6 Electrical Characteristics, ATL431Bx, ATL432Bx
over recommended operating conditions, TA = 25°C (unless otherwise noted)
PARAMETER
MIN
TYP
MAX
UNIT
2487
2500
2512
mV
ATL43xBI; TA =
–40°C to 85°C
5
15
ATL43xBQ; TA =
–40°C to 125°C
6
34
ΔVKA = 10 V − Vref
–0.4
–2.7
ΔVKA = 36 V − 10 V
–0.1
–2
IKA = 1 mA, R1 = 10 kΩ, R2 = ∞
30
150
nA
Figure 23
IKA = 1 mA, R1 = 10 kΩ, R2 = ∞
20
50
nA
Minimum cathode current for
regulation
Figure 22
Figure 5
VKA = Vref
20
35
µA
Ioff
Off-state cathode current
Figure 24
VKA = 36 V, Vref = 0
0.05
0.2
µA
|zKA|
Dynamic impedance, see
section
Figure 22
VKA = Vref, f ≤ 1 kHz, IKA = 1 mA to 100 mA
0.05
0.3
Ω
Vref
Reference voltage
VI(dev)
TEST CIRCUIT
TEST CONDITIONS
Figure 22
VKA = Vref, IKA = 1 mA
Deviation of reference input
voltage over full temperature
range, see section
Figure 22
VKA = Vref, IKA = 1
mA
ΔVref /
ΔVKA
Ratio of change in reference
voltage to the change in
cathode voltage
Figure 23
IKA = 1 mA
Iref
Reference input current
Figure 23
II(dev)
Deviation of reference input
current over full temperature
range, see section
Imin
4
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mV
mV/V
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6.7 Typical Characteristics
Data at high and low temperatures are applicable only within the recommended operating free-air temperature ranges of the
various devices.
0.04
2520
Vref = 2485mV
Vref = 2500mV
Vref = 2504mV
2515
2510
0.032
IREF (PA)
Vref (mV)
2505
2500
2495
0.024
0.016
2490
2485
0.008
2480
2475
-40
-20
0
20
40
60
TA (qC)
80
100
120
0
-40
140
-20
0
20
40
60
TA (qC)
80
100
120
140
IKA=1mA
Figure 2. Reference Current vs Free-Air Temperature
Figure 1. Reference Voltage vs Free-Air Temperature
100
40
TA = -40qC
TA = 25qC
TA = 85qC
TA = 125qC
80
60
30
40
IKA (PA)
IKA (mA)
20
0
-20
20
-40
10
-60
-80
-100
-1.5
0
-1
-0.5
0
0.5
1
1.5
VKA = VREF (V)
2
2.5
3
0
0.5
1
D001
1.5
2
VKA = VREF (V)
2.5
3
D001
Figure 4. Cathode Current vs Cathode Voltage
Figure 3. Cathode Current vs Cathode Voltage
0.2
30
0.16
25
IOFF (PA)
IKA (PA)
Ik(min)
20
15
10
2.3
0.12
0.08
0.04
2.35
2.4
2.45
VKA = VREF (V)
2.5
2.55
Figure 5. Cathode Current vs Cathode Voltage
0
-40
-20
0
20
40
60
TA (qC)
80
100
120
140
Figure 6. Off-State Cathode Current vs Free-Air Temperature
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Typical Characteristics (continued)
Data at high and low temperatures are applicable only within the recommended operating free-air temperature ranges of the
various devices.
-0.1
0
-0.5
-0.15
-1
-0.2
'Vref/'Vka (mV)
-1.5
'Vref (mV)
-2
-2.5
-3
-3.5
-4
Vref to 10V
10V to 36V
-0.25
-0.3
-0.35
-0.4
-4.5
-5
-0.45
-5.5
-0.5
-40
-6
0
5
10
15
20
Vka (V)
25
30
35
40
IKA=1mA
-20
0
20
40
60
80
Temperature (qC)
100
140
D001
IKA=1mA
Figure 7. Delta Reference Voltage vs Cathode Voltage
Figure 8. Delta Reference Voltage vs Cathode Voltage
900
180
Gain
Phase
160
Gain (dB) and Phase (ƒ)
840
Noise (nV/—Hz)
120
780
720
660
140
120
100
80
60
40
20
0
±20
600
10
100
1000
Frequency (Hz)
10
10000
100
1000
10000
100000
1000000
Frequency (Hz)
D001
IKA = 1 mA
C001
Figure 25 used for this measurement.
Figure 9. Noise Voltage
IKA=1mA
Figure 10. Small-Signal Voltage Amplification vs Frequency
0.1
1.2
1.1
0.08
Output Impedance (:)
Output Impedance (:)
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.06
0.04
0.02
0.2
0.1
0
100
1000
10000
Frequency (Hz)
100000
1000000
Figure 26 used for this measurement.
-20
0
20
40
60
TA (qC)
80
100
120
140
Figure 26 used for this measurement.
Figure 11. Output Impedance vs Frequency
6
0
-40
Figure 12. DC Output Impedance vs Temperature
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Typical Characteristics (continued)
Data at high and low temperatures are applicable only within the recommended operating free-air temperature ranges of the
various devices.
2000
1000
Unstable
IKA(PA)
STABLE
100
STABLE
20
0.0001
0.001
ESR < 20 mΩ
IKA = 100 µA
0.01
0.1
CKA(PF)
1
10
D001
Figure 27 used to verify stability.
Figure 28 used for this measurement.
Figure 13. Pulse Response
Figure 14. Low IKA (VKA = 2.5 V) Stability Boundary
Conditions all ATL43xx Devices
2000
2000
1000
1000
Unstable
Unstable
STABLE
IKA(PA)
IKA(PA)
STABLE
100
100
STABLE
20
0.0001
0.001
ESR < 20 mΩ
0.01
0.1
CKA(PF)
1
STABLE
20
0.0001
10
0.001
D001
Figure 27 used to verify stability.
ESR < 20 mΩ
Figure 15. Low IKA (VKA = 5.0 V) Stability Boundary
Conditions all ATL43xx Devices
0.01
0.1
CKA(PF)
1
10
D001
Figure 27 used to verify stability.
Figure 16. Low IKA (VKA = 10.0 V) Stability Boundary
Conditions all ATL43xx Devices
100
2000
IKA(mA)
IKA(PA)
1000
STABLE
Unstable
10
100
Stable
20
0.0001
0.001
ESR < 20mΩ
0.01
0.1
CKA(PF)
1
10
1
0.0001
0.001
D001
Figure 27 used to verify stability.
Figure 17. Low IKA (VKA = 15.0 V) Stability Boundary
Conditions all ATL43xx Devices
ESR < 20 mΩ
0.01
0.1
CKA(uF)
1
10
D001
Figure 27 used to verify stability.
Figure 18. High IKA (VKA = 2.5 V) Stability Boundary
Conditions all ATL43xx Devices
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Typical Characteristics (continued)
Data at high and low temperatures are applicable only within the recommended operating free-air temperature ranges of the
various devices.
100
100
IKA(mA)
IKA(mA)
Stable
10
Stable
10
Unstable
1
0.0001
0.001
ESR < 20 mΩ
0.01
0.1
CKA(uF)
1
Unstable
1
0.0001
10
0.001
0.01
0.1
CKA(uF)
D001
Figure 27 used to verify stability.
ESR < 20 mΩ
Figure 19. High IKA (VKA = 5.0 V) Stability Boundary
Conditions all ATL43xx Devices
1
10
D001
Figure 27 used to verify stability.
Figure 20. High IKA (VKA = 10.0 V) Stability Boundary
Conditions all ATL43xx Devices
IKA(mA)
100
10
1
0.0001
Stable
0.001
ESR < 20 mΩ
0.01
0.1
CKA(uF)
1
10
D001
Figure 27 used to verify stability.
Figure 21. High IKA (VKA = 15.0 V) Stability Boundary Conditions all ATL43xx Devices
8
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7 Parameter Measurement Information
The deviation parameters Vref(dev) and Iref(dev) are defined as the differences between the maximum and minimum
values obtained over the rated temperature range. The average full-range temperature coefficient of the
reference input voltage αVref is defined as:
αVref is positive or negative, depending on whether minimum Vref or maximum Vref, respectively, occurs at the
lower temperature.
|zKA| =
∆VKA
∆I
The dynamic impedance is defined as:
When the device is operating with two external resistors (see Figure 23), the total dynamic impedance of the
KA
circuit is given by:
|z'| = ∆V
∆I
which is approximately equal to
VKA
Input
(
|zKA| 1 + R1
R2
(
Input
VKA
IKA
IKA
Vref
R1
Iref
R2
Vref
Figure 23. Test Circuit for VKA > Vref
Figure 22. Test Circuit for VKA = Vref
Input
R1 ö
æ
VKA = Vref ç 1 +
÷ + Iref × R1
R2 ø
è
VKA
Ioff
IK= 1mA
15 kQ
2.5 k
100 µF
VDC = 7.57 V
15 kQ
Figure 24. Test Circuit for Ioff
Figure 25. Test Circuit for Phase and Gain Measurement
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Parameter Measurement Information (continued)
>250Ÿ
10 F
+
IK
R1 = 10NŸ
+
CL
-
R2
Vbat
>250Ÿ
IK
+
Vbat
CL
-
Figure 26. Test Circuit for Reference Impedance (ZKA)
Figure 27. Test Circuit for Stability Boundary Conditions
25NŸ
OUTPUT
IK
Pulse
Generator
F = 100kHz
50 Ÿ
GND
Figure 28. Test Circuit for Pulse Response
10
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8 Detailed Description
8.1 Overview
ATL43x is a low power counterpart to TL431 and TLV431, having lower minimum cathode current (Ik(min) = 35
µA). Like TL431, ATL43x is used in conjunction with it's key components to behave as a single voltage
reference, error amplifier, voltage clamp or comparator with integrated reference.
ATL43x can be operated and adjusted to cathode voltages from 2.5 V to 36 V, making this part optimum for a
wide range of end equipments in industrial, auto, telecom and computing. In order for this device to behave as a
shunt regulator or error amplifier, > 35 µA (Imin(max)) must be supplied in to the cathode pin. Under this
condition, feedback can be applied from the Cathode and Ref pins to create a replica of the internal reference
voltage.
Various reference voltage options can be purchased with initial tolerances (at 25°C) of 0.5% and 1.0%. These
reference options are denoted by B (0.5%) and A (1.0%) after the ATL43x.
The ATL43xxI devices are characterized for operation from –40°C to +85°C, and the ATL43xxQ devices are
characterized for operation from –40°C to +125°C.
8.2 Functional Block Diagram
CATHODE
REF
+
Vref
ANODE
8.3 Feature Description
ATL43x consists of an internal reference and amplifier that outputs a sink current based on the difference
between the reference pin and the virtual internal pin. The sink current is produced by an internal Darlington pair.
When operated with enough voltage headroom (≥ 2.5 V) and cathode current (IKA), ATL43x forces the reference
pin to 2.5 V. However, the reference pin can not be left floating, as it needs Iref ≥ 0.1 µA (please see the
Functional Block Diagram). This is because the reference pin is driven into an NPN, which needs base current in
order operate properly.
When feedback is applied from the Cathode and Reference pins, ATL43x behaves as a Zener diode, regulating
to a constant voltage dependent on current being supplied into the cathode. This is due to the internal amplifier
and reference entering the proper operating regions. The same amount of current needed in the above feedback
situation must be applied to this device in open loop, servo or error amplifying implementations in order for it to
be in the proper linear region giving ATL43x enough gain.
Unlike many linear regulators, ATL43x is internally compensated to be stable without an output capacitor
between the cathode and anode; however, if it is desired to use an output capacitor Figure 14 through Figure 21
can be used as a guide to assist in choosing the correct capacitor to maintain stability.
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8.4 Device Functional Modes
8.4.1 Open Loop (Comparator)
When the cathode/output voltage or current of ATL43x is not being fed back to the reference/input pin in any
form, this device is operating in open loop. With such high gain in this configuration, ATL43x is typically used as
a comparator. Due to the integrated reference, the ATL43x allows users to monitor a certain level of a single
signal.
8.4.2 Closed Loop
When the cathode/output voltage or current of ATL43x is being fed back to the reference/input pin in any form,
this device is operating in closed loop. The majority of applications involving ATL43x use it in this manner to
regulate a fixed voltage or current. The feedback enables this device to behave as an error amplifier, computing
a portion of the output voltage and adjusting it to maintain the desired regulation. This is done by relating the
output voltage back to the reference pin in a manner to make it equal to the internal reference voltage, which can
be accomplished via resistive or direct feedback.
12
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9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
Figure 29 shows the ATL43x used in a 24-V isolated flyback supply. The output of the regulator, plus the forward
voltage drop of the optocoupler LED (2.5 + 0.7 = 3.2 V), determine the minimum voltage that can be regulated in
an isolated supply configuration. Regulated voltage as low as 5.0 Vdc is possible in the topology shown in
Figure 29.
The 431 family of devices are prevalent in these applications, being designers go-to choice for secondary side
regulation. Due to this prevalence, this section will further go on to explain operation and design in both states of
ATL43x that this application will see, open loop (Comparator + Vref) and closed loop (Shunt Regulator).
ATL43x's key benefit in isolated supplies is the no load power savings gained by the > 20x decrease in IKmin from
TL431. More information about this and other benefits can be found in Designing with the "Advanced" TL431,
ATL431, SLVA685. Further information about system stability and using a ATL43x device for compensation can
be found in Compensation Design With TL431 for UCC28600, SLUA671.
VI
120 V
Vo=24 V
Gate Drive
VCC
Ibias
Controller
VFB
Current
Sense
GND
ATL431
Figure 29. Flyback With Isolation Using ATL43x
as Voltage Reference and Error Amplifier
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9.2 Typical Applications
9.2.1 Comparator With Integrated Reference (Open Loop)
Vsup
Rsup
Vout
CATHODE
R1
VL
RIN
REF
VIN
+
R2
2.5V
ANODE
Figure 30. Comparator Application Schematic
9.2.1.1 Design Requirements
For this design example, use the parameters listed in Table 1 as the input parameters.
Table 1. Design Parameters
DESIGN PARAMETER
EXAMPLE VALUE
Input voltage range
0 V to 3.3 V
Input resistance
100 kΩ
Supply voltage
5V
Cathode current (IK)
50 µA
High output voltage level (Vin < 2.5 V)
Vsup
Low output voltage (Vin > 2.5 V)
~2 V
9.2.1.2 Detailed Design Procedure
When using ATL43x as a comparator with reference, determine the following:
• Input voltage range
• Reference voltage accuracy
• Output logic input high and low level thresholds
• Current source resistance
9.2.1.2.1 Basic Operation
In the configuration shown in Figure 30 ATL43x will behave as a comparator, comparing the Vref pin voltage to
the internal virtual reference voltage. When provided a proper cathode current (Ik), ATL43x will have enough
open loop gain to provide a quick response. With the ATL43x's max operating current (Imin) being 35 µA and up
to 40 µA over temperature, operation below that could result in low gain, leading to a slow response.
14
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9.2.1.2.2 Overdrive
Slow or inaccurate responses can also occur when the reference pin is not provided enough overdrive voltage.
This is the amount of voltage that is higher than the internal virtual reference. The internal virtual reference
voltage will be within the range of 2.5 V ±(0.5% or 1.0%) depending on which version is being used.
The more overdrive voltage provided, the faster the ATL43x will respond.
For applications where ATL43x is being used as a comparator, it is best to set the trip point to greater than the
positive expected error (that is, +1.0% for the A version). For fast response, setting the trip point to > 10% of the
internal Vref should suffice. Figure 31 shows the transition from VOH to VOL based on the input voltage and can be
used as a guide for selecting the overdrive voltage.
For minimal voltage drop or difference from Vin to the ref pin, it is recommended to use an input resistor < 1 MΩ
to provide Iref.
9.2.1.2.3 Output Voltage and Logic Input Level
In order for ATL43x to properly be used as a comparator, the logic output must be readable by the receiving logic
device. This is accomplished by knowing the input high and low level threshold voltage levels, typically denoted
by VIH and VIL.
As seen in Figure 31, ATL43x's output low level voltage in open-loop/comparator mode is ~2 V, which is
sufficient for some ≥ 5.0 V supplied logic. However, would not work for 3.3 V and 1.8 V supplied logic. In order to
accommodate this, a resistive divider can be tied to the output to attenuate the output voltage to a voltage legible
to the receiving low voltage logic device.
ATL43x's output high voltage is approximately Vsup due to ATL43x being open-collector. If Vsup is much higher
than the receiving logic's maximum input voltage tolerance, the output must be attenuated to accommodate the
outgoing logic's reliability.
When using a resistive divider on the output, be sure to make the sum of the resistive divider (R1 and R2 in
Figure 30) is much greater than Rsup in order to not interfere with ATL43x's ability to pull close to Vsup when
turning off.
9.2.1.2.3.1 Input Resistance
ATL43x requires an input resistance in this application in order to source the reference current (Iref) needed from
this device to be in the proper operating regions while turning on. The actual voltage seen at the ref pin will be:
Vref = Vin – Iref × Rin
(1)
Because Iref can be as high as 0.15 µA, TI recommends to use a resistance small enough that will mitigate the
error that Iref creates from Vin. Also, the input resistance must be set high enough as to not surpass the absolute
maximum of 10 mA.
VOUT (V)
9.2.1.3 Application Curve
5.5
5.25
5
4.75
4.5
4.25
4
3.75
3.5
3.25
3
2.75
2.5
2.25
2
1.75
1.5
2
2.1
2.2
2.3
2.4
2.5 2.6
VIN (V)
2.7
2.8
2.9
3
D001
RIN = 100 kΩ
VSUP = 5.0 V
RSUP = 10 kΩ
Figure 31. Open Loop (Comparator Mode) VOUT vs VIN
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9.2.2 Shunt Regulator/Reference
RSUP
VSUP
VO = ( 1 +
R1
0.1%
R2
) VREF
CATHODE
REF
VREF
R1
R2
0.1%
ATL431
CL
ANODE
Figure 32. Shunt Regulator Schematic
9.2.2.1 Design Requirements
For this design example, use the parameters listed in Table 2 as the input parameters.
Table 2. Design Parameters
DESIGN PARAMETER
EXAMPLE VALUE
Reference initial accuracy
1.0%
Supply voltage
48 V
Cathode current (IK)
50 µA
Output voltage level
2.5 V to 36 V
Load capacitance
1 nF
Feedback resistor values (R1 and R2)
10 kΩ
9.2.2.2 Detailed Design Procedure
When using ATL43x as a Shunt Regulator, determine the following:
• Input voltage range
• Temperature range
• Total accuracy
• Cathode current
• Reference initial accuracy
• Output capacitance
9.2.2.2.1
Programming Output/Cathode Voltage
In order to program the cathode voltage to a regulated voltage a resistive bridge must be shunted between the
cathode and anode pins with the mid point tied to the reference pin. This can be seen in Figure 32, with R1 and
R2 being the resistive bridge. The cathode/output voltage in the shunt regulator configuration can be
approximated by the equation shown in Figure 32. The cathode voltage can be more accurately determined by
taking in to account the cathode current:
VO = (1 + R1 / R2) × Vref – Iref × R1
(2)
For this equation to be valid, ATL43x must be fully biased so that it has enough open loop gain to mitigate any
gain error. This can be done by meeting the Imin spec denoted in Electrical Characteristics, ATL431Ax, ATL432Ax
table.
9.2.2.2.2 Total Accuracy
When programming the output above unity gain (VKA = Vref), ATL43x is susceptible to other errors that may effect
the overall accuracy beyond Vref. These errors include:
•
•
•
16
R1 and R2 accuracies
VI(dev) - Change in reference voltage over temperature
ΔVref / ΔVKA - Change in reference voltage to the change in cathode voltage
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|zKA| - Dynamic impedance, causing a change in cathode voltage with cathode current
Worst case cathode voltage can be determined taking all of the variables in to account. Setting the Shunt
Voltage on an Adjustable Shunt, SLVA445, assists designers in setting the shunt voltage to achieve optimum
accuracy for this device.
9.2.2.2.3 Stability
Though ATL43x is stable with no capacitive load, the device that receives the shunt regulator's output voltage
could present a capacitive load that is within the ATL43x region of stability, shown in Figure 14 through
Figure 21. Also, designers may use capacitive loads to improve the transient response or for power supply
decoupling.
Figure 14 through Figure 21 should be used as a guide for capacitor selection and compensation. It is
characterized using ceramic capacitors with very-low ESR. When it is desirable to use a capacitor within the
unstable region, higher ESR capacitors can be used to stabilize ATL43x or an external series resistance can be
added. For more information and guidance on ESR values, see Designing with the "Advanced" TL431, ATL431,
SLVA685.
Unlike TL431, the stability boundary is characterized and determined with resistors 250 Ω and greater. Which is
more suitable for low cathode current applications.
9.2.2.3 Application Curves
Figure 33. ATL43x Start-up Response IKA = 50 µA
Figure 34. ATL43x Start-up Response IKA = 1 mA
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10 Power Supply Recommendations
When using ATL43x in a flyback supply (see Figure 29) it is often common for designers to place the bias
resistor between the Anode of the Opto-Coupler and the output voltage (VO = 24 V). However, this makes
ATL43x more susceptible to EOS/ESD damage. Therefore, TI recommends to place the bias resistor between
the Cathodes of the Opto-Coupler and ATL43x, as shown in Figure 29. For further explanation, see Designing
with the "Advanced" TL431, ATL431, SLVA685.
When using ATL43x as a Linear Regulator to supply a load, designers will typically use a bypass capacitor on
the output/cathode pin. Be sure that the capacitance is within the stability criteria shown in Figure 14 through
Figure 21.
To not exceed the maximum cathode current, be sure that the supply voltage is current limited. Also, be sure to
limit the current being driven into the Ref pin, as not to exceed it's absolute maximum rating.
For applications shunting high currents, pay attention to the cathode and anode trace lengths, adjusting the width
of the traces to have the proper current density.
11 Layout
11.1 Layout Guidelines
Place decoupling capacitors as close to the device as possible. Use appropriate widths for traces when shunting
high currents to avoid excessive voltage drops.
11.2 Layout Example
DBZ
(TOP VIEW)
Rref
Vin
REF
1
Rsup
Vsup
ANODE
3
CATHODE
GND
2
CL
GND
Figure 35. DBZ Layout Example
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12 Device and Documentation Support
12.1 Related Links
The table below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to sample or buy.
Table 3. Related Links
PARTS
PRODUCT FOLDER
SAMPLE & BUY
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
ATL431
Click here
Click here
Click here
Click here
Click here
ATL432
Click here
Click here
Click here
Click here
Click here
12.2 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
12.3 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
12.4 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
12.5 Electrostatic Discharge Caution
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
12.6 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
13 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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PACKAGE OPTION ADDENDUM
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10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
(3)
Device Marking
(4/5)
(6)
ATL431AIDBZR
ACTIVE
SOT-23
DBZ
3
3000
RoHS & Green NIPDAU | NIPDAUAG
Level-1-260C-UNLIM
-40 to 85
(ZCKS, ZCR3)
ATL431AQDBZR
ACTIVE
SOT-23
DBZ
3
3000
RoHS & Green NIPDAU | NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
(ZCLS, ZCS3)
ATL431BIDBZR
ACTIVE
SOT-23
DBZ
3
3000
RoHS & Green NIPDAU | NIPDAUAG
Level-1-260C-UNLIM
-40 to 85
(ZCMS, ZCT3)
ATL431BQDBZR
ACTIVE
SOT-23
DBZ
3
3000
RoHS & Green NIPDAU | NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
(ZCJS, ZCU3)
ATL432AIDBZR
ACTIVE
SOT-23
DBZ
3
3000
RoHS & Green NIPDAU | NIPDAUAG
Level-1-260C-UNLIM
-40 to 85
(ZCNS, ZCV3)
ATL432AQDBZR
ACTIVE
SOT-23
DBZ
3
3000
RoHS & Green NIPDAU | NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
(ZCOS, ZCW3)
ATL432BIDBZR
ACTIVE
SOT-23
DBZ
3
3000
RoHS & Green NIPDAU | NIPDAUAG
Level-1-260C-UNLIM
-40 to 85
(ZCPS, ZCX3)
ATL432BQDBZR
ACTIVE
SOT-23
DBZ
3
3000
RoHS & Green NIPDAU | NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
(ZCQS, ZCY3)
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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