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U2481B/ U2482B
Multiple Automotive Lamp-Outage Monitor, VT = 3.5 mV
Description
The U2481B and the U2482B multicomparator circuits are designed to monitor automotive illumination by sensing the voltage drop across shunt resistors. Equipped with extremely low comparator thresholds, these ICs can be used together as a chip set to build an entire lamp monitor system. Single operation of both circuits is also possible. As a special feature for brake-lamp monitoring, the U2481B contains a latch stage connected to one of its triple comparators. With - 4 single comparators - 1 double comparator and - 2 triple comparators each of the integrated circuits monitors up to 12 lamps and up to 6 fuses. All comparator stages are combined together to control the common output stage.
Features
D Extremely low comparator thresholds of typically
3.5 mV
Benefits
D Extremely low threshold voltage gives low voltage
drop via shunt resistor. Power dissipation of the lamp monitor module is minimized
D Internal compensation for copper shunts D Internal compensation for voltage-dependent
bulb characteristic
D Perfect EMC in conjunction with an appropriate
pc board layout
D Comparator input voltage may exceed supply voltage D Internal protection measures for pulses
according to ISO TR 7637/1
D ESD according to MIL-SID-883 C test method 3015.7
- Human body model: 4 kV - Machine model: 200 V EMI protection (TEM cell up to 100 V/m)
Applications
Both ICs can be used in any kind of vehicle with a 12-V supply. It is sufficient to insert small resistors into the lamp wiring and to provide the dashboard instrument cluster with a pilot lamp. These ICs increase safety and add comfort features.
Ordering Information
Extended Type Number U2481B-FL U2482B-FL Package SO28 SO28 Remarks
Rev. A3, 21-Jun-99
1 (12)
U2481B/ U2482B
Block Diagram
VB 20 REFK1 IN1K1 28 Ref 27 E1 + - IT IT VB K1 13 mV Voltage drift of comparator threshold IT = f (VB) Power on Reset POR IT Divider REFK2 IN1K2 1 2 Ref K2 13 mV E1 Cl1 Cl2 Clock 1 Clock 2 2-TOsc 20-TOsc Oscillator 15 OSC VS Stabilized voltage Vstab = 5.2 V 19 VS
REFK3 IN1K3 IN2K3 IN3K3 INFK3
7 6 8 9 26
Ref K3 3.5 mV E1 E2 E3 Cl2 Up down counter T = 1.2 s Start High at forward counter end High at Start return counter zero Cl1 Ref K4 3.5 mV E1 14 OUT Set Out Reset VS
REFK4 IN1K4
24 25
INFK5
16
REFK5 IN1K5 IN2K5
4 3 5 VB
Ref K5 3.5 mV E1 E2 + - Out Reset POR Latch for stoplamps Set K6 Ref 3.5 mV Up down counter T = 1.2 s High at Start forward counter end Start High at return counter zero Cl1 * VS * Connection to GND only for U2482B (latch disabled) E1
17 INFK6
22 REFK6 21 IN1K6
INF
23
REFK7 IN1K7 IN2K7 IN3K7
11 10 12 13
Ref K7 E1 E2 E3
3.5 mV
Cl2
18 GND
94 8833
Figure 1.
2 (12)
Rev. A3, 21-Jun-99
U2481B/ U2482B
Pin Description
REFK2 1 28 REFK1 Pin 1 2 3 4 5 6 7 8 9 10 11 IN1K3 6 23 INF 12 REFK3 7 22 REFK6 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 IN2K7 IN3K7 OUT OSC INFK5 INFK6 GND VS VB IN1K6 REFK6 INF REFK4 IN1K4 INFK3 IN1K1 REFK1 Symbol REFK2 IN1K2 IN1K5 REFK5 IN2K5 IN1K3 REFK3 IN2K3 IN3K3 IN1K7 REFK7 Function Reference for threshold voltage single comparator K2 Input 1; single comparator K2 Input 1; double comparator K5 Reference for threshold voltage; double comparator K5 Input 2; double comparator K5 Input 1; triple comparator K3 Reference for threshold voltage; triple comparator K3 Input 2; triple comparator K3 Input 3; triple comparator K3 Input 1; triple comparator K7 (U2481B with latch) Reference for threshold voltage; triple comparator K7 (U2481B with latch) Input 2; triple comparator K7 (U2481B with latch) Input 3; triple comparator K7 (U2481B with latch) Output for pilot lamp R/C combination for oscillator Fuse monitor input ; double comparator K5 Fuse monitor input; single comparator K6 Ground Supply voltage Reference voltage of comparators Input1; single comparator K6 Reference for threshold voltage; single comparator K6 Input; brake-fuse comparator Reference for threshold voltage; single comparator K4 Input 1; single comparator K4 Fuse monitor input; triple comparator K3 Input 1; single comparator K1 Reference for threshold voltage; single comparator K1
IN1K2
2
27
IN1K1
In1K5
3
26
INFK3
REFK5
4
25
IN1K4
IN2K5
5
24
REFK4
IN2K3
8
21
IN1K6
IN3K3
9
20
VB
IN1K7
10
19
VS
REFK7
11
18
GND
IN2K7 12
17
INFK6
IN3K7 13
16
INFK5
OUT
14
94 8831
15
OSC
Figure 2. Pin configuration
Rev. A3, 21-Jun-99
3 (12)
U2481B/ U2482B
150 W 1000 W VBatt R2 C2 C1 15 mF R1
0.1 mF
VB 20
VS 19 15 Osc Cosc 10 nF Rosc 82 kW
28 A 1 kW Fuse 2 kW 100 kW 1 Fuse 2 kW 2 100 kW 2 kW 16 4 1 kW Shunt B 2 kW Shunt 2 kW
95 10689
27
U2481B U2482B
Pilot lamp 1.2 W
14
Out
Kl 61
3
5 18 GND
A: Example of 2 "single comparators" using the fuses as shunt resistors. (Both comparators are internally EXOR connected, see block diagram.) B: Example of a "double comparator" using copper shunts and additional fuse monitoring
Figure 3. Basic application diagram
4 (12)
Rev. A3, 21-Jun-99
U2481B/ U2482B
Functional Description
Power Supply, Pins 19 and 20
The ICs have two supply pins. The IC itself is supplied via Pin 19 (stabilized voltage, POR-circuitry). Pin 20 supplies only the current sources of the comparators. Both pins have an an internal 21-V Zener diode for protection. For reasons of interference protection, and surge immunity, the supply voltage pins have to be provided with RC-circuitries as shown in figure 3. The resistors limit the current in the case of overvoltage, whereas the capacitors smooth the supply voltage. Recommended values: Pin 19: Pin 20: R1 = 150 W; C1 = 15 mF A bulb is detected as "good" as long as the voltage drop via the shunt resistor exceeds the threshold voltage. If the pilot lamp is off, a failed bulb is detected if the voltage drop via the shunt resistor is smaller than the threshold voltage. If the pilot lamp is on, an external transistor is necessary to drive the pilot lamp. Monitoring is disabled when the lamps are switched off, therefore the comparator outputs are disabled if the reference voltage Vref < VMin with VMin = 0.33 VB. As protection against transients on the supply, all comparator inputs require external resistors. Their tolerances directly influence the comparator threshold accuracy. Resistors with a 1% tolerance are recommended.
R2 = 1000 W; C2 = 0.1 mF
"
An external diode protects the IC against battery reversal.
Power-on Reset
When the supply voltage is switched on, a power-on-reset pulse is generated internally which resets the brake lamp monitor latch and the counter stages.
Single comparators: The inputs (K1, K2, K4, K6) sink currents of typically 10 mA each. During switch-over, the currents of reference and input pins are identical. Therefore, identical external protection resistors (R = 1 kW) are required. Double comparator: The reference input (K5) sinks a current of typically 20 mA; its inputs sink currents of typically 10 mA each during switch-over. Therefore, the external protection resistors must provide R = 1 kW for REFK5 and R = 2 kW each for IN1K5 and IN2K5. Triple comparators: The reference inputs (K3 and K7) sink currents of typically 30 mA. All inputs (IN1K3, IN2K3 IN3K3, and IN1K7, IN2K7, IN3K7) sink the identical typical current of 10 mA during switch-over. Therefore, the external protection resistor must provide R = 1 kW for REFK3 and REFK7 and R = 3 kW at each input.
Oscillator, Pin 15
The RC-oscillator is the time base for clock 1 and clock 2 (see block diagram) which are desired from a divider stage and fed to the two upward and downward counters. The oscillator frequency fosc is mainly determined by the external R/C components and an integrated resistor. The capacitor Cosc is charged by the external resistor and discharged by the integrated one. Because of the temperature characteristic and the tolerances of the integrated 2 kW-resistor, the external one has to have considerable higher value in order to achieve a stable frequency. Calculation of the frequency: f osc
+ t1 + c
osc
osc
1 (0.74 R osc
) 2260 W)
Fuse Monitoring
The internal EXOR conjunction of comparators K1 and K2 allows fuse monitoring for both lamps. Even a simultaneous blowout of both fuses is detected. The pins INFK3, INFK5 and INFK6 with their EXOR gates can be used for additional fuse monitoring. Detection threshold for a blown fuse is Vref < VMin with VMin = 0.33 VB (VB = reference voltage of comparators). Pin INF is used for brake fuse monitoring. With a voltage drop VF > 4.8 V across the fuse, the comparator detects a blown fuse. A voltage drop VF < 2.8 V represents a "good" fuse. U2481B's comparator, K7, is connected to a latch, thus a brake lamp outage is memorized.
With the recommended values Rosc = 82 kW and Cosc = 10 nF fosc 1.58 kHz
Comparators
Comparators K1 and K2: threshold voltage of typically Vth = 13 mV; designed to monitor high- and low-beam bulbs, where the fuses can be used as shunt resistors. Comparators K3 to K7: threshold voltage of typically Vth = 3.5 mV; designed for all other monitor purposes. Due to the integrated compensation circuitry, these comparators are suitable for pc layer copper shunts.
Rev. A3, 21-Jun-99
5 (12)
U2481B/ U2482B
Integrated Delay, Debouncing, Failure Display
As soon as a comparator detects a failure, a slow upward counter is started in order to generate the delay time, tdel = 1.2 s. During consistent failure, the output stage is enabled after tdel. If the failure disappears during tdel, a fast downward counter is started in order to generate the 135 ms. The upward counter is reset, reset time treset the output stage stays disabled.
Latch for Brake Lamp Monitor
A failure of a brake lamp detected by comparator K7 or a blown fuse in the brake circuitry is memorized after the delay time has expired. A reset of the latch can only be performed with a "poweron-reset".
y
Output Stage
The output is a PNP Darlington stage with protection diodes to VS and IC ground. The output is designed to drive an external pilot lamp with an external NPN transistor. At the end of the delay time, the output stage is switched on and can source a current of Iout = -10 mA with a typical saturation voltage of Vsat = 1 V.
Benefits: Intermittent contacts in the wire harness do not activate the pilot lamp! Even cyclical intermittent contacts are screened out as long as the pulse/pause ratio is smaller than 10:1. In the case of higher duty cycles the upward counter may reach its trigger threshold for the output activation after t > tdel. Individual delay- and reset times can be adjusted with external R/C components according to (see "oscillator") - - tdel = 1930 x tosc treset = 198 x tosc
Test Mode
With VTEST = 23 V (20 mA) applied to Pin osc, via a 200 W resistor the delay time stage can be bypassed for test purposes. A failure detection will be displayed immediately to save time during threshold testing.
6 (12)
Rev. A3, 21-Jun-99
U2481B/ U2482B
Application Hints
Layout Recommendations for Copper Layer Shunts
Lamp-outage monitor systems can be produced most cost-efficiently if stamped shunt resistors are replaced by copper layer shunts which are generated with the pc board layout. The U2481B and the U2482B are suitable for this application because of their comparator thresholds, which are compensated in reference to the temperature characteristic of copper. A constant lamp current, ILAMP = VTh/Rsh with threshold voltage VTh = f(T) and shunt resistor Rsh = f(T), is achieved if the comparator threshold and the shunt resistor have identical temperature characteristics. With the temperature coefficient of copper acu = 3.9 10-3 1/K, a copper shunt changes its nominal value by 52% if the automotive ambient temperature range of tamb = -40 to +95C is taken into consideration. Examples for sheet resistances of copper shunts (Tamb = 25C): RA = 0.5 mW/square (35.1 mm layer thickness) RA = 0.25 mW/square (70 mm layer thickness) Two equations for calculation of the shunt resistance: Rshunt = RA L/Wcn (with RA = Cu sheet resistance) Rshunt = VTh / 1/2 ILAMP Therefore, the length of copper shunt is calculated as: L = 2 VTh Wcn / RA ILAMP L = 215 mm For a reasonable pc-layout, a meander-shaped shunt resistor is recommended. The high lamp currents may cause hot spots at sharp edges of the copper shunts. That may deteriorate accuracy of the measurement. Therefore it is recommended to layout the copper shunts with smoothed curves. According to figure 4, the meander may be formed by 4 straight tracks (length LS each) and 3 connecting 180 ares (length L are each). If the mean arc radius is selected to r = Wcn the are length becomes Lare = p Wcn. Therefore, the total length is L = 4 LS + 3 Lare = 4 LS + 3
p
Wcn
With L = 215 mm, the track length becomes LS
How to Lay Out Copper Shunts (figure 4)
The width of the copper trace has to be selected in reference to a low-current-effected temperature increase. The copper trace must be capable of peak currents which do not blow the fuse. The peak currents are specified by the car manufacturers. Example: A 7.5-A fuse allows a peak current of 26 A (1 s), 15 A (10 s) or 10 A (60 s). The copper shunt length has to be calculated between the two sense connections to the comparator. The connection of the common reference input of double and triple comparators has to be considered carefully. There is calculation example for a copper shunt used with a 4-W bulb. ILAMP = 0.325 A Failure criterion: I = 1/2 ILAMP 10-A fuse is capable of I = 13.5 A Copper layer thickness: 70 mm Comparator threshold voltage (U2481B, U2482B): VTh = 3.5 mV Assumed copper width for temperature increase DTcu < 50C: Wcu = 2.5 mm (13.5 A, 70 mm)
+ 41 (L * 3
p
W cn)
LS = 47.8 mm
Using Fuses as Shunt Resistors
This cost-saving method can be used if the following assumptions are fulfilled: - - Each lamp needs a dedicated fuse The fuse socket is mounted within the monitor module to connect the sense lines are suitable for this monitor Both integrated circuits are suitable for this monitor task because of their comparator thresholds arecompensated for the fuse temperature coefficient of aF = 4.1 10-3 1/K
-
Calculation Example for a 55-W Bulb and a
7.5-A fuse:
Measured voltage drop across the fuse: VF = 52 mV Measured current: ILAMP = 4.2 A Calculated resistance: RF = 12.4 mW Selected comparatore threshold: VTh = 1/4 VF = 13 mV (typically); With a lamp current ILAMP < VTh/RF =< 1.05 A the comparator detects a blown fuse.
Rev. A3, 21-Jun-99
7 (12)
U2481B/ U2482B
Wcn = 2.5 mm to lamp to lamp switch
LS
Larc Wcn
R2
R1
28
27
26
25
24
23
22
21
20
19
18
17
16
15
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Figure 4. Design example for a copper shunt with meander shape
Absolute Maximum Ratings
Parameters Supply voltage Pulse current (2 ms) Short circuit current (reversed battery) Output current Ambient temperature range Storage temperature range Junction temperature Symbol VS, VBatt IS ISC Iout Tamb Tstg Tj Value 16.5 1.1 170 -12 -40 to +100 -55 to +125 150 Unit V A mA mA C C C
Thermal Resistance
Parameters Thermal resistance SO 28 Symbol RthJA Value 110 Unit K/W
8 (12)
Rev. A3, 21-Jun-99
94 8832
U2481B U2482B
U2481B/ U2482B
Electrical Characteristics
VBatt (Kl. 15) = 10 to 15 V, Tamb = -40 to +100_C, supply series resistors and input protection resistors connected (see figure 1 "Block diagram" and figure 3 "Basic application schematic") unless otherwise specified. Parameters Supply Operating voltage Supply current Test Conditions / Pins Symbol VBatt VBatt = 13 V, V14 = low Pin 20 Pin 19 Tamb = 25C Pin 19 VBatt (Kl. 15) Pins 27, 28 Pins 1, 2 Pins 24, 25 Pins 21, 22 Pin 7 Pins 6, 8, 9 Pin 11 Pins 10,12,13 Pin 4 Pins 3,5 VS = 10 V Pins 1, 2, 27, 28 VS = 13 V VS = 15 V VBatt = 13 V I27, I28 I 1 , I2 I24, I25 I21, I22 I7 I 6 , I8 , I9 I11 I10,I12,I13 I4 I 3 , I5 VT1x
x = Pin No.
Min. 9 0.3 3 3.0 3.7
Typ.
Max. 16
Unit V mA mA V V
0.7 5
Power on reset (POR) Comparators Comparator input current during switch over
1.1 7 4.2 5.0
Comparator thresholds VT1 of comparators K1 and K2 (VT1 = VRef... - VIN...) Voltage characteristic Temperature characteristic Comparator thresholds VT2 of comparators K3 to K7 (VT2 = VRef... - VIN...)
DVT1 DTT1
8.5 10.0 11.0
10 10 10 10 30 10 30 10 20 10 11.5 13.0 14.0 0.5 3900
mA
14.5 16.0 17.0
mV mV/V ppm/K
Pins 6, 7, 8, 9 Pins 24, 25 Pins 3, 4, 5 Pins 21, 22 Pins 10, 11, 12, 13 VS = 10 V VS = 13 V VS = 15 V
VT1x x = Pin No.
Voltage characteristic Temperature characteristic Min. comparator input voltage for detection Output Output current Output saturation voltage
DVT2 DTT2
VMin
1.5 2.0 2.3
all Ref-pins
3.0 3.5 3.8 0.17 3900 0.33 VBatt -10.0 1.0
4.5 5.0 5.3
mV mV/V ppm/K V
VBatt = 13 V Iout = -10 mA Pin 19-Pin 14
Pin 14
I14 VSat
1.5
mA V
Rev. A3, 21-Jun-99
9 (12)
U2481B/ U2482B
Parameters Protection Voltage of Zener diodes Test Conditions / Pins Pin 19 Pin 20 all Ref... and IN... pins Symbol VS VB VRef..., VIN... fosc Pin 15 td tdb Pin 23 V23 = 13 V Pin 23 Pins 16, 17, 26 VTB I23 VTTx
x=16,17,26
Min.
Typ. 21 19 19 1.58
Max.
Unit
V
Oscillator Oscillator frequency Delay time Debounce time Break fuse Brake fuse detection threshold Input current Trigger threshold (internal pull-down resistor) Input current Test Test voltage for delay time override
Rosc = 82 kW, Cosc = 10 nF, Rosc = 82 kW, Cosc = 10 nF Rosc = 82 kW, Cosc = 10 nF
kHz
1.1 115 2.8
1.2 125 3.8 100 0.33 VBatt 100 23
1.3 135 4.8
s ms V
mA
V
VBatt = 13 V Pin 16, 17, 26 I = 20 mA Pin 15
Ix V15
mA
V
10 (12)
Rev. A3, 21-Jun-99
U2481B/ U2482B
Package Information
Package SO28
Dimensions in mm
18.05 17.80 9.15 8.65 7.5 7.3
2.35 0.4 1.27 28 16.51 15 0.25 0.10 0.25 10.50 10.20
technical drawings according to DIN specifications 13033
1
14
Rev. A3, 21-Jun-99
11 (12)
U2481B/ U2482B
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It is the policy of TEMIC Semiconductor GmbH to 1. Meet all present and future national and international statutory requirements. 2. Regularly and continuously improve the performance of our products, processes, distribution and operating systems with respect to their impact on the health and safety of our employees and the public, as well as their impact on the environment. It is particular concern to control or eliminate releases of those substances into the atmosphere which are known as ozone depleting substances ( ODSs). The Montreal Protocol ( 1987) and its London Amendments ( 1990) intend to severely restrict the use of ODSs and forbid their use within the next ten years. Various national and international initiatives are pressing for an earlier ban on these substances. TEMIC Semiconductor GmbH has been able to use its policy of continuous improvements to eliminate the use of ODSs listed in the following documents. 1. Annex A, B and list of transitional substances of the Montreal Protocol and the London Amendments respectively 2 . Class I and II ozone depleting substances in the Clean Air Act Amendments of 1990 by the Environmental Protection Agency ( EPA) in the USA 3. Council Decision 88/540/EEC and 91/690/EEC Annex A, B and C ( transitional substances ) respectively. TEMIC Semiconductor GmbH can certify that our semiconductors are not manufactured with ozone depleting substances and do not contain such substances.
We reserve the right to make changes to improve technical design and may do so without further notice. Parameters can vary in different applications. All operating parameters must be validated for each customer application by the customer. Should the buyer use TEMIC Semiconductors products for any unintended or unauthorized application, the buyer shall indemnify TEMIC Semiconductors against all claims, costs, damages, and expenses, arising out of, directly or indirectly, any claim of personal damage, injury or death associated with such unintended or unauthorized use. TEMIC Semiconductor GmbH, P.O.B. 3535, D-74025 Heilbronn, Germany Telephone: 49 ( 0 ) 7131 67 2594, Fax number: 49 ( 0 ) 7131 67 2423
12 (12)
Rev. A3, 21-Jun-99

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