A1205 Datasheet

A1205
Continuous-Time Bipolar Switch
FEATURES AND BENEFITS
DESCRIPTION
• Ideal for applications that require pulsing VCC to
conserve power
• 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
Packages:
3 pin SOT23W (LH)
The Allegro™ A1205 Hall-effect bipolar switch is a nextgeneration replacement and extension of the popular Allegro
A3134 bipolar switch. The A1205 has identical specifications
as the A1201 but is recommended for applications that require
pulsing VCC to conserve power. For standard applications,
where VCC is constant, please refer to the A1201 through
A1204 devices.
Overall, the A120x family, produced with BiCMOS technology,
consists of continuous-time devices that feature 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 low-offset amplifiers
help to minimize noise and to reduce the residual offset
voltage normally caused by device overmolding, temperature
excursions, and thermal stress.
3 pin SIP (UA)
The A120x Hall-effect bipolar switches include 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.
Not to scale
Continued on the next page…
VCC
To all subcircuits
Regulator
VOUT
Amp
Gain
Offset
Trim
Control
GND
Functional Block Diagram
A12051-DS, Rev. 9
A1205
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 miniature thin-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.
SPECIFICATIONS
Selection Guide
Part Number
Packing*
Mounting
A1205LLHLT-T
7-in. reel, 3000 pieces/reel
3-pin SOT23W surface mount
A1205LLHLX-T
13-in. reel, 10000 pieces/reel
3-pin SOT23W surface mount
A1205LUA-T
Bulk, 500 pieces/bag
3-pin SIP through hole
Ambient, TA
BRP (Min)
BOP (Max)
–40ºC to 150ºC
–50
50
*Contact Allegro for additional packing options.
Absolute Maximum Ratings
Characteristic
Symbol
Notes
Rating
Units
Supply Voltage
VCC
30
V
Reverse Supply Voltage
VRCC
–30
V
Output Off Voltage
VOUT
30
V
Reverse Output Voltage
VROUT
–0.5
V
IOUTSINK
25
mA
Magnetic Flux Density
Output Current Sink
B
Unlimited
G
Operating Ambient Temperature
TA
Range E
–40 to 85
ºC
Range L
–40 to 150
ºC
Maximum Junction Temperature
TJ(max)
165
ºC
Tstg
–65 to 170
ºC
GND
Storage Temperature
2
3
VOUT
VOUT
Package LH Pin-out Diagram
1
GND
2
VCC
1
VCC
3
Package UA Pin-out Diagram
Terminal List
Number
Package LH
Package UA
1
1
2
3
3
2
Name
VCC
VOUT
GND
Description
Connects power supply to chip
Output from circuit
Ground
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
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A1205
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
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 + 5 G or B < BRP
–5G
–
–
4
µs
tr
VCC = 12 V, RLOAD = 820 Ω, CS = 12 pF
–
–
2
µs
tf
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
tPO
Output Rise Time3
Output Fall Time3
Supply Current
Reverse Battery Current
IRCC
Supply Zener Clamp Voltage
VZ
ICC = 30 mA; TA = 25°C
32
–
40
V
Supply Zener Current
IZ
VZ = 32 V; TA = 25°C
–
–
30
mA
50
G
Magnetic Characteristics4
Operate Point
BOP
South pole adjacent to branded face of device
–40
15
Release Point
BRP
North pole adjacent to branded face of device
–50
–15
40
G
Hysteresis
BHYS
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 2.5 V/μs, and TA = 150°C, the Power-On Time can reach its maximum value.
3 C =oscilloscope probe capacitance.
S
4 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 alge-
braic 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). Reference to the magnetic field polarity
is with respect to the beveled face of the device.
DEVICE QUALIFICATION PROGRAM
Contact Allegro for information.
EMC (ELECTROMAGNETIC COMPATABILITY) REQUIREMENTS
Contact Allegro for information.
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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A1205
Continuous-Time Bipolar Switch
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic
Symbol
Package Thermal Resistance
Test Conditions*
RθJA
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
Maximum Allowable VCC (V)
*Additional thermal information available on Allegro Web site.
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, 1-layer PCB
(R JA = 228 ºC/W)
Package UA, 1-layer PCB
(R JA = 165 ºC/W)
Package LH, 2-layer PCB
(R JA = 110 ºC/W)
VCC(min)
20
40
60
80
100
120
140
160
180
Power Dissipation, PD (m W)
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
2l
(R aye
rP
θJ
C
A =
11 B, P
0 º ac
1-la
C/ ka
W
(R yer PC
) ge L
θJA =
B
H
165 , Pac
ºC/ kage
W)
UA
1-lay
er P
(R
CB,
θJA =
228 Packag
ºC/W
e LH
)
20
40
60
80
100
120
Temperature (°C)
140
160
180
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
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A1205
Continuous-Time Bipolar Switch
CHARACTERISTIC DATA
Supply Current (On) versus Ambient Temperature
8.0
8.0
7.0
7.0
VCC (V)
5.0
24
3.8
4.0
3.0
6.0
ICCON (mA)
6.0
ICCON (mA)
Supply Current (On) versus Supply Voltage
–40
25
150
4.0
3.0
2.0
2.0
1.0
1.0
0
TA (°C)
5.0
0
–50
0
50
TA (°C)
100
150
0
15
20
25
Supply Current (Off) versus Supply Voltage
8.0
8.0
7.0
7.0
6.0
VCC (V)
5.0
24
3.8
4.0
3.0
ICCOFF (mA)
ICCOFF (mA)
10
VCC (V)
Supply Current (Off) versus Ambient Temperature
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
ILOAD = 20 mA
350
5
VCC (V)
Output Voltage (On) versus Ambient Temperature
ILOAD = 20 mA
350
300
300
250
VCC (V)
200
24
3.8
150
100
250
TA (°C)
VOUT(SAT) (mV)
VOUT(SAT) (mV)
5
200
–40
25
150
150
100
50
50
0
0
–50
0
50
TA (°C)
100
150
0
5
10
15
20
25
VCC (V)
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A1205
Continuous-Time Bipolar Switch
Operate Point versus Ambient Temperature
50
40
40
30
30
VCC (V)
10
24
12
3.8
0
–10
–20
TA (°C)
20
BOP (G)
20
BOP (G)
Operate Point versus Supply Voltage
50
–40
25
150
10
0
-10
-20
–30
-30
–40
–50
0
50
TA (°C)
100
-40
150
0
15
20
25
25
Release Point versus Supply Voltage
40
40
30
30
20
20
VCC (V)
0
24
12
3.8
–10
–20
–30
TA (°C)
10
BRP (G)
10
BRP (G)
10
Supply Voltage (V)
Release Point versus Ambient Temperature
–40
25
150
0
-10
-20
-30
–40
-40
–50
–50
0
50
TA (°C)
100
-50
150
0
10
15
20
25
25
Hysteresis versus Supply Voltage
55
55
50
50
45
45
35
VCC (V)
30
24
12
3.8
25
20
15
BHYS (G)
40
40
TA (°C)
35
–40
25
150
30
25
20
15
10
10
5
–50
5
Supply Voltage (V)
Hysteresis versus Ambient Temperature
BHYS (G)
5
0
50
TA (°C)
100
150
5
0
5
10
15
20
25
25
Supply Voltage (V)
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115 Northeast Cutoff
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A1205
Continuous-Time Bipolar Switch
FUNCTIONAL DESCRIPTION
Bipolar Device Switching
The devices of the A120X family provide 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.)
ing 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 the field is
reduced beyond the BOP level, the device switches back to the low
state.
The typical output behavior of the A120x devices is latching.
However, the A120x family 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
A120x family allows clean switching of the output, even in the
presence of external mechanical vibration and electrical noise.
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.
VS
VCC
A120x
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 exhibit(A)
GND
(D)
(C)
V+
V+
VOUT
B+
B–
0
BRP
BHYS
B+
BOP
BRP
B– 0
VOUT(SAT)
0
BOP
BOP
BHYS
VOUT(SAT)
0
BRP
B+
0
Switch to High
Switch to High
VOUT
VOUT(SAT)
VCC
Switch to Low
Switch to Low
VOUT
VCC
Switch to Low
Switch to High
VCC
B–
Output
VOUT
(B)
V+
0
RL
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 120x family, can operate in any of the three modes.
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A1205
Continuous-Time Bipolar Switch
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.
in order to conserve power (refer to figure 2). 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 Bipolar switches, refer to Application
Note 27705, Understanding Bipolar Hall Effect Sensor ICs.
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 BENEFITS
Continuous-time devices, such as the A120x family, offer the
fastest available power-on settling time and frequency response.
Due to offsets generated during the IC packaging process,
continuous-time devices typically require programming after
packaging to tighten magnetic parameter distributions. In contrast, chopper-stabilized 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
chopper-stabilization offset cancellation algorithm.
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
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
1
2
All are provided in Allegro Electronic Data Book, AMS-702, and
the Allegro Web site, www.allegromicro.com.
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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A1205
Continuous-Time Bipolar Switch
POWER DERATING
PD = VCC × ICC = 12 V × 4 mA = 48 mW
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, RθJA, 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, RθJC, is relatively
small component of RθJA. 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)
ΔT = PD × RθJA (2)
TJ = TA + ΔT
(3)
For example, given common conditions such as: TA= 25°C,
VCC = 12 V, ICC = 4 mA, and RθJA = 140 °C/W, then:
ΔT = PD × RθJA = 48 mW × 140 °C/W = 7°C
TJ = TA + ΔT = 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 RθJA and TA.
Example: Reliability for VCC at TA = 150°C, package UA, using
minimum-K PCB.
Observe the worst-case ratings for the device, specifically: RθJA = 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:
ΔTmax = 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) = ΔTmax ÷ RθJA = 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
RθJA. If VCC(est) ≥ VCC(max), then operation between VCC(est) and
VCC(max) is reliable under these conditions.
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A1205
Continuous-Time Bipolar Switch
CUSTOMER PACKAGE DRAWINGS
For Reference Only – Not for Tooling Use
(Reference DWG-2840)
Dimensions in millimeters – NOT TO SCALE
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
+0.12
2.98 –0.08
D
1.49
4° ±4°
A
3
+0.020
0.180 –0.053
0.96
D
+0.19
1.91 –0.06
+0.10
2.90 –0.20
2.40
0.70
D
0.25 MIN
1.00
2
1
0.55 REF
0.25 BSC
0.95
Seating Plane
Branded Face
Gauge Plane
B
PCB Layout Reference View
8X 10°
REF
1.00 ±0.13
NNT
+0.10
0.05 –0.05
0.95 BSC
0.40 ±0.10
A Active Area Depth, 0.28 mm
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
N = Last three digits of device part number
T = Temperature Code (Letter)
C
Standard Branding Reference View
C Branding scale and appearance at supplier discretion
D Hall elements, not to scale
Figure 3: Package LH, 3-Pin (SOT-23W)
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A1205
Continuous-Time Bipolar Switch
For Reference Only – Not for Tooling Use
(Reference DWG-9049)
Dimensions in millimeters – NOT TO SCALE
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
45°
B
4.09
+0.08
–0.05
1.52 ±0.05
E
2.04
C
2 X 10°
1.44 E
3.02
E
Mold Ejector
Pin Indent
+0.08
–0.05
45°
Branded
Face
2.16 MAX
0.51 REF
A
1
2
0.79 REF
3
0.43
+0.05
–0.07
0.41
+0.03
–0.06
1.27 NOM
NNT
15.75 ±0.25
1
D
Standard Branding Reference View
= Supplier emblem
N = Last three digits of device part number
T = Temperature code
A
Dambar removal protrusion (6X)
B
Gate and tie bar burr area
C
Active Area Depth, 0.50 mm REF
D
Branding scale and appearance at supplier discretion
E
Hall element, not to scale
Package UA, 3-Pin SIP
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115 Northeast Cutoff
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A1205
Continuous-Time Bipolar Switch
Revision History
Revision
Revision Date
8
January 1, 2015
9
July 13, 2015
Description of Revision
Added LX option to Selection Guide
Corrected LH package Active Area Depth value
Copyright ©2006-2015, Allegro MicroSystems, LLC
Allegro MicroSystems, LLC 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 any devices or systems, including but not limited to life support devices or systems, in which a failure of
Allegro’s product can reasonably be expected to cause bodily harm.
The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, LLC 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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