A1201: Continuous-Time Bipolar Switch

A1201
Continuous-Time Bipolar Switch
Features and Benefits
Description
▪ Continuous-time operation
▫ Fast power-on time
▫ Low noise
▪ Stable operation over full operating temperature range
▪ Reverse battery protection
▪ Solid-state reliability
▪ Factory-programmed at end-of-line for optimum
performance
▪ Robust EMC performance
▪ High ESD rating
▪ Regulator stability without a bypass capacitor
The Allegro® A1201 Hall-effect bipolar switch is a nextgeneration replacement and extension of the popular Allegro
A3134 bipolar switch. Overall, the A1201, produced with
BiCMOS technology, is a continuous-time device that
features fast power-on time and low-noise operation. Device
programming is performed after packaging, to ensure increased
switchpoint accuracy by eliminating offsets that can be induced
by package stress. Unique Hall element geometries and lowoffset amplifiers help to minimize noise and to reduce the
residual offset voltage normally caused by device overmolding,
temperature excursions, and thermal stress.
The A1201 Hall-effect bipolar switch includes the following on
a single silicon chip: voltage regulator, Hall-voltage generator,
small-signal amplifier, Schmitt trigger, and NMOS output
transistor. The integrated voltage regulator permits operation
from 3.8 to 24 V. The extensive on-board protection circuitry
makes possible a ±30 V absolute maximum voltage rating for
superior protection in automotive and motor commutation
applications, without adding external components. The device
is a member of the A1201 product family which has identical
electrical characteristics throughout, but provides a range of
magnetic switchpoints.
Packages: 3 pin SOT23W (suffix LH), and
3 pin SIP (suffix UA)
Continued on the next page…
Not to scale
Functional Block Diagram
VCC
To all subcircuits
Regulator
VOUT
Amp
Gain
Offset
Trim
Control
GND
A1201-DS, Rev. 14
A1201
Continuous-Time Bipolar Switch
Description (continued)
The small geometries of the BiCMOS process allow these devices
to be provided in ultrasmall packages. The package styles available
provide magnetically optimized solutions for most applications.
Package LH is a SOT23W, a miniature low-profile surface-mount
package, while package UA is a three-lead ultramini SIP for throughhole mounting. Each package is lead (Pb) free, with 100% matte
tin plated leadframes.
Selection Guide
Part Number
Packing1
Mounting
Ambient, TA
A1201ELHLT-T2
7-in. reel, 3000 pieces/reel
3-pin SOT23W surface mount
–40ºC to 85ºC
Bulk, 500 pieces/bag
3-pin SIP through hole
7-in. reel, 3000 pieces/reel
3-pin SOT23W surface mount
Bulk, 500 pieces/bag
3-pin SIP through hole
A1201EUA-T2
A1201LLHLT-T2
A1201LUA-T2
BRP (Min)
BOP (Max)
–50
50
–40ºC to 150ºC
1Contact Allegro
for additional packing options.
2Variant is obsolete.
Absolute Maximum Ratings
Rating
Units
Supply Voltage
Characteristic
VCC
30
V
Reverse Supply Voltage
VRCC
–30
V
Output Off Voltage
VOUT
30
V
VROUT
–0.5
V
IOUTSINK
25
mA
Reverse Output Voltage
Output Current Sink
Magnetic Flux Density
Symbol
Notes
Unlimited
G
Range E
–40 to 85
ºC
Range L
–40 to 150
ºC
B
Operating Ambient Temperature
TA
Maximum Junction Temperature
TJ(max)
165
ºC
Tstg
–65 to 170
ºC
Storage Temperature
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
2
A1201
Continuous-Time Bipolar Switch
Pin-out Diagrams
Package UA
GND
Package LH
2
3
VOUT
VOUT
1
GND
2
VCC
1
VCC
3
Terminal List
Name
VCC
VOUT
GND
Description
Connects power supply to chip
Output from circuit
Ground
Number
Package LH Package UA
1
1
2
3
3
2
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
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3
A1201
Continuous-Time Bipolar Switch
OPERATING CHARACTERISTICS over full operating voltage and ambient temperature ranges, unless otherwise noted
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Electrical Characteristics
Supply Voltage1
Output Leakage Current
Output On Voltage
Power-On Time2
Output Rise Time3
Output Fall
Time3
Supply Current
Reverse Battery Current
VCC
Operating, TJ < 165°C
3.8
–
24
V
IOUTOFF
VOUT = 24 V, B < BRP
–
–
10
μA
VOUT(SAT)
IOUT = 20 mA, B > BOP
–
215
400
mV
Slew rate (dVCC/dt) < 2.5 V/μs, B > BOP(max) + 5 G
or B < BRP(min) – 5 G
–
–
4
μs
tr
VCC = 12 V, RLOAD = 820 Ω, CS = 12 pF
–
–
2
μs
tf
tPO
VCC = 12 V, RLOAD = 820 Ω, CS = 12 pF
–
–
2
μs
ICCON
B > BOP
–
3.8
7.5
mA
ICCOFF
B < BRP
–
3.5
7.5
mA
VRCC = –30 V
–
–
–10
mA
IRCC
Supply Zener Clamp Voltage
VZ
ICC = 30 mA; TA = 25°C
32
–
–
V
Supply Zener Current4
IZ
VZ = 32 V; TA = 25°C
–
–
30
mA
Magnetic
Characteristics5
Operate Point
BOP
A1201
South pole adjacent to branded face
of device
–40
15
50
G
Release Point
BRP
A1201
North pole adjacent to branded face
of device
–50
–15
40
G
Hysteresis
BHYS
A1201
BOP – BRP
5
30
55
G
1
Maximum voltage must be adjusted for power dissipation and junction temperature, see Power Derating section.
2 For V
CC slew rates greater than 250 V/μs, and TA = 150°C, the Power-On Time can reach its maximum value.
3 C =oscilloscope probe capacitance.
S
4 Maximum current limit is equal to the maximum I
CC(max) + 22 mA.
5 Magnetic flux density, B, is indicated as a negative value for north-polarity magnetic fields, and as a positive value for south-polarity magnetic fields.
This so-called algebraic convention supports arithmetic comparison of north and south polarity values, where the relative strength of the field is indicated
by the absolute value of B, and the sign indicates the polarity of the field (for example, a –100 G field and a 100 G field have equivalent strength, but
opposite polarity).
DEVICE QUALIFICATION PROGRAM
Contact Allegro for information.
EMC (Electromagnetic Compatibility) REQUIREMENTS
Contact Allegro for information.
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
4
A1201
Continuous-Time Bipolar Switch
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic
Symbol
Test Conditions
RθJA
Maximum Allowable VCC (V)
Package Thermal Resistance
Value Units
Package LH, 1-layer PCB with copper limited to solder pads
228
ºC/W
Package LH, 2-layer PCB with 0.463 in.2 of copper area each
side connected by thermal vias
110
ºC/W
Package UA, 1-layer PCB with copper limited to solder pads
165
ºC/W
Power Derating Curve
TJ(max) = 165ºC; ICC = ICC(max)
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
VCC(max)
Package LH, 2-layer PCB
(RQJA = 110 ºC/W)
Package UA, 1-layer PCB
(RQJA = 165 ºC/W)
Package LH, 1-layer PCB
(RQJA = 228 ºC/W)
VCC(min)
20
40
60
80
100
120
140
160
180
Power Dissipation, PD (mW)
Power Dissipation versus Ambient Temperature
1900
1800
1700
1600
1500
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
Pa
(R cka
ge
QJ
A =
L
11 H, 2
0 º -la
Pac
C/ ye
W
(R kage
) r PC
UA
QJA =
B
,
165 1-la
ºC/ yer
W)
PC
B
Pac
k
(R age LH
,
QJA =
228 1-laye
ºC/W r PC
B
)
20
40
60
80
100
120
Temperature (°C)
140
160
180
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
5
A1201
Continuous-Time Bipolar Switch
Characteristic Data
Supply Current (On) versus Ambient Temperature
Supply Current (On) versus Supply Voltage
(A1201)
(A1201)
8.0
7.0
7.0
ICCON (mA)
6.0
VCC (V)
5.0
24
3.8
4.0
3.0
ICCON (mA)
8.0
6.0
TA (°C)
5.0
–40
25
150
4.0
3.0
2.0
2.0
1.0
1.0
0
0
–50
0
50
TA (°C)
100
150
0
5
10
Supply Current (Off) versus Ambient Temperature
25
(A1201)
8.0
7.0
7.0
VCC (V)
5.0
24
3.8
4.0
3.0
ICCOFF (mA)
8.0
6.0
ICCOFF (mA)
20
Supply Current (Off) versus Supply Voltage
(A1201)
6.0
TA (°C)
5.0
–40
25
150
4.0
3.0
2.0
2.0
1.0
1.0
0
0
–50
0
50
TA (°C)
100
0
150
10
15
20
25
Output Voltage (On) versus Supply Voltage
(A1201)
400
5
VCC (V)
Output Voltage (On) versus Ambient Temperature
(A1201)
400
350
350
300
300
250
VCC (V)
200
24
3.8
150
100
50
VOUT(SAT) (mV)
VOUT(SAT) (mV)
15
VCC (V)
TA (°C)
250
–40
25
150
200
150
100
50
0
0
–50
0
50
TA (°C)
100
150
0
5
10
15
20
25
VCC (V)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
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www.allegromicro.com
6
A1201
Continuous-Time Bipolar Switch
Operate Point versus Ambient Temperature
Operate Point versus Supply Voltage
(A1201)
50
40
40
30
30
20
20
VCC (V)
10
24
12
3.8
0
-10
BOP (G)
BOP (G)
(A1201)
50
–40
25
150
0
-10
-20
-20
-30
-30
-40
TA (°C)
10
-40
-50
0
50
TA (°C)
100
150
0
20
25
(A1201)
40
30
30
20
20
10
24
12
3.8
-10
-20
BRP (G)
VCC (V)
0
–40
25
150
-10
-20
-30
-30
-40
-40
-50
TA (°C)
0
-50
-50
0
50
100
150
0
5
10
15
20
TA (°C)
VCC (V)
Hysteresis versus Ambient Temperature
Hysteresis versus Supply Voltage
(A1201)
55
(A1201)
55
50
50
45
45
40
VCC (V)
35
24
12
3.8
30
25
40
TA (°C)
35
–40
25
150
30
25
20
20
15
15
10
10
5
25
BHYS (G)
BRP (G)
15
Release Point versus Supply Voltage
(A1201)
10
BHYS (G)
10
VCC (V)
Release Point versus Ambient Temperature
40
5
5
-50
0
50
TA (°C)
100
150
0
5
10
15
20
25
VCC (V)
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115 Northeast Cutoff, Box 15036
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7
A1201
Continuous-Time Bipolar Switch
Functional Description
Bipolar Device Switching
The A1201 provides highly sensitive switching for applications using magnetic fields of alternating polarities, such as ring
magnets. There are three switching modes for bipolar devices,
referred to as latch, unipolar switch, and negative switch. Mode
is determined by the switchpoint characteristics of the individual
device. The characteristic hysteresis, BHYS , of the device, is the
difference in the relative magnetic strength and polarity of the
switchpoints of the device. (Note that, in the following descriptions, a negative magnetic value indicates a north polarity field,
and a positive magnetic value indicates a south polarity field.
For a given value of magnetic strength, BX , the values –BX and
BX indicate two fields of equal strength, but opposite polarity.
B = 0 indicates the absence of a magnetic field.)
In contrast to latching, when a device exhibits unipolar switching, it only responds to a south magnetic field. The field must
be of sufficient strength, > BOP , for the device to operate. When
the field is reduced beyond the BRP level, the device switches
back to the high state, as shown in panel B of figure 1. Devices
exhibiting negative switch behavior operate in a similar but
opposite manner. A north polarity field of sufficient strength,
> BRP , (more north than BRP) is required for operation, although
the result is that VOUT switches high, as shown in panel C. When
VS
VCC
Bipolar devices typically behave as latches. In this mode,
magnetic fields of opposite polarity and equivalent strengths
are needed to switch the output. When the magnetic fields are
removed (B  0) the device remains in the same state until a
magnetic field of the opposite polarity and of sufficient strength
causes it to switch. The hysteresis of latch mode behavior is
shown in panel A of figure 1.
A1201
RL
Output
VOUT
GND
(D)
(B)
BRP
BHYS
VCC
VOUT
Switch to High
Switch to High
VOUT
VOUT
VOUT(SAT)
B– 0
V+
B+
0
VOUT(SAT)
B–
BOP
B+
0
BOP
BHYS
BOP
0
VCC
Switch to Low
VOUT(SAT)
B–
V+
Switch to Low
0
Switch to Low
Switch to High
VCC
BRP
V+
(C)
BRP
(A)
0
B+
BHYS
Figure 1. Bipolar Device Output Switching Modes. These behaviors can be exhibited when using a circuit such as that shown in panel D. Panel A
displays the hysteresis when a device exhibits latch mode (note that the BHYS band incorporates B= 0), panel B shows unipolar switch behavior (the
BHYS band is more positive than B = 0), and panel C shows negative switch behavior (the BHYS band is more negative than B = 0). Bipolar devices,
such as the A1201, can operate in any of the three modes.
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115 Northeast Cutoff, Box 15036
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8
A1201
Continuous-Time Bipolar Switch
the field is reduced beyond the BOP level, the device switches
back to the low state.
Bipolar devices adopt an indeterminate output state when powered-on in the absence of a magnetic field or in a field that lies
within the hysteresis band of the device.
The typical output behavior of the A1201 device is latching.
That is, switching to the low state when the magnetic field at the
Hall element exceeds the operate point threshold, BOP . At this
point, the output voltage is VOUT(SAT). When the magnetic field
is reduced to below the release point threshold, BRP , the device
output, VOUT , goes high. The values of the magnetic parameters
are specified in the Magnetic Characteristics table, on page 3.
Note that, as shown in figure 1, these switchpoints can lie in
either north or south polarity ranges.
For more information on Bipolar switches, refer to Application
Note 27705, Understanding Bipolar Hall Effect Sensor ICs.
CONTINUOUS-TIME BENEFITS
Continuous-time devices, such as the A1201, offer the fastest
available power-on settling time and frequency response. Due to
offsets generated during the IC packaging process, continuoustime devices typically require programming after packaging to
tighten magnetic parameter distributions. In contrast, chopperstabilized switches employ an offset cancellation technique
on the chip that eliminates these offsets without the need for
after-packaging programming. The tradeoff is a longer settling
time and reduced frequency response as a result of the chopperstabilization offset cancellation algorithm.
The A1201 is designed to attain a small hysteresis, and thereby
provide more sensitive switching. Although this means that
true latching behavior cannot be guaranteed in all cases, proper
switching can be ensured by use of both south and north magnetic fields, as in a ring magnet. The hysteresis of the A1201
allows clean switching of the output, even in the presence of
external mechanical vibration and electrical noise.
1
2
3
4
5
VCC
t
VOUT
t
tPO(max)
Output Sampled
Figure 2. Continuous-Time Application, B < BRP.. This figure illustrates the use of a quick cycle for chopping VCC in order to conserve battery power.
Position 1, power is applied to the device. Position 2, the output assumes the correct state at a time prior to the maximum Power-On Time, tPO(max).
The case shown is where the correct output state is HIGH . Position 3, tPO(max) has elapsed. The device output is valid. Position 4, after the output is
valid, a control unit reads the output. Position 5, power is removed from the device.
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9
A1201
The choice between continuous-time and chopper-stabilized
designs is solely determined by the application. Battery management is an example where continuous-time is often required. In
these applications, VCC is chopped with a very small duty cycle
in order to conserve power (refer to figure 4). The duty cycle
is controlled by the power-on time, tPO, of the device. Because
continuous-time devices have the shorter power-on time, they
are the clear choice for such applications.
For more information on the chopper stabilization technique,
refer to Technical Paper STP 97-10, Monolithic Magnetic Hall
Sensing Using Dynamic Quadrature Offset Cancellation and
Technical Paper STP 99-1, Chopper-Stabilized Amplifiers with a
Track-and-Hold Signal Demodulator.
Continuous-Time Bipolar Switch
ADDITIONAL APPLICATIONS INFORMATION
Extensive applications information for Hall-effect devices is
available in:
• Hall-Effect IC Applications Guide, Application Note 27701
• Hall-Effect Devices: Gluing, Potting, Encapsulating, Lead
Welding and Lead Forming, Application Note 27703.1
• Soldering Methods for Allegro’s Products – SMT and ThroughHole, Application Note 26009
All are provided in Allegro Electronic Data Book, AMS-702,
and the Allegro Web site, www.allegromicro.com.
10
Allegro MicroSystems, Inc.
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A1201
Continuous-Time Bipolar Switch
Power Derating
Power Derating
The device must be operated below the maximum junction
temperature of the device, TJ(max). Under certain combinations of
peak conditions, reliable operation may require derating supplied power or improving the heat dissipation properties of the
application. This section presents a procedure for correlating
factors affecting operating TJ. (Thermal data is also available on
the Allegro MicroSystems Web site.)
The Package Thermal Resistance, RJA, is a figure of merit summarizing the ability of the application and the device to dissipate
heat from the junction (die), through all paths to the ambient air.
Its primary component is the Effective Thermal Conductivity,
K, of the printed circuit board, including adjacent devices and
traces. Radiation from the die through the device case, RJC, is
relatively small component of RJA. Ambient air temperature,
TA, and air motion are significant external factors, damped by
overmolding.
The effect of varying power levels (Power Dissipation, PD), can
be estimated. The following formulas represent the fundamental
relationships used to estimate TJ, at PD.
PD = VIN × IIN

(1)
T = PD × RJA (2)
TJ = TA + ΔT
Example: Reliability for VCC at TA = 150°C, package UA, using
minimum-K PCB.
Observe the worst-case ratings for the device, specifically:
RJA = 165°C/W, TJ(max) = 165°C, VCC(max) = 24 V, and
ICC(max) = 7.5 mA.
Calculate the maximum allowable power level, PD(max). First,
invert equation 3:
Tmax = TJ(max) – TA = 165 °C – 150 °C = 15 °C
This provides the allowable increase to TJ resulting from internal
power dissipation. Then, invert equation 2:
PD(max) = Tmax ÷ RJA = 15°C ÷ 165 °C/W = 91 mW
Finally, invert equation 1 with respect to voltage:
VCC(est) = PD(max) ÷ ICC(max) = 91 mW ÷ 7.5 mA = 12.1 V
The result indicates that, at TA, the application and device can
dissipate adequate amounts of heat at voltages ≤VCC(est).
Compare VCC(est) to VCC(max). If VCC(est) ≤ VCC(max), then reliable operation between VCC(est) and VCC(max) requires enhanced
RJA. If VCC(est) ≥ VCC(max), then operation between VCC(est) and
VCC(max) is reliable under these conditions.
(3)
For example, given common conditions such as: TA= 25°C,
VCC = 12 V, ICC = 4 mA, and RJA = 140 °C/W, then:
PD = VCC × ICC = 12 V × 4 mA = 48 mW

T = PD × RJA = 48 mW × 140 °C/W = 7°C
TJ = TA + T = 25°C + 7°C = 32°C
A worst-case estimate, PD(max), represents the maximum allowable power level (VCC(max), ICC(max)), without exceeding TJ(max),
at a selected RJA and TA.
11
Allegro MicroSystems, Inc.
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A1201
Continuous-Time Bipolar Switch
Package LH, 3-Pin (SOT-23W)
+0.12
2.98 –0.08
1.49 D
4°±4°
3
A
+0.020
0.180–0.053
0.96 D
+0.10
2.90 –0.20
+0.19
1.91 –0.06
2.40
0.70
D
0.25 MIN
1.00
2
1
0.55 REF
0.25 BSC
0.95
Seating Plane
Gauge Plane
8X 10° REF
B
PCB Layout Reference View
Branded Face
1.00 ±0.13
+0.10
0.05 –0.05
0.95 BSC
0.40 ±0.10
For Reference Only; not for tooling use (reference dwg. 802840)
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
A
Active Area Depth, 0.28 mm REF
B
Reference land pattern layout
All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary
to meet application process requirements and PCB layout tolerances
C
Branding scale and appearance at supplier discretion
D
Hall element, not to scale
NNT
1
C
Standard Branding Reference View
N = Last two digits of device part number
T = Temperature code
12
Allegro MicroSystems, Inc.
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A1201
Continuous-Time Bipolar Switch
Package UA, 3-Pin SIP
+0.08
4.09 –0.05
45°
B
C
E
2.04
1.52 ±0.05
1.44 E
Mold Ejector
Pin Indent
+0.08
3.02 –0.05
E
Branded
Face
45°
1
2.16
MAX
D Standard Branding Reference View
= Supplier emblem
N = Last two digits of device part number
T = Temperature code
0.79 REF
A
0.51
REF
NNT
1
2
3
+0.03
0.41 –0.06
15.75 ±0.51
For Reference Only; not for tooling use (reference DWG-9049)
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
A
Dambar removal protrusion (6X)
B Gate burr area
C Active Area Depth, 0.50 mm REF
+0.05
0.43 –0.07
D
Branding scale and appearance at supplier discretion
E
Hall element, not to scale
1.27 NOM
Copyright ©2005-2009, Allegro MicroSystems, Inc.Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from
the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current.
Allegro’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the
failure of that life support device or system, or to affect the safety or effectiveness of that device or system.
The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use;
nor for any infringement of patents or other rights of third parties which may result from its use.
For the latest version of this document, visit our website:
www.allegromicro.com
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Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
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