4721D–AUTO–05/12
Features
●Temperature and supply voltage compensated flashing frequency
●Frequency doubling indicates lamp outage
●Two relay driver outputs with high current-carrying capacity and low saturation
voltage
●Minimum lamp load for flasher operation: ≥ 1W
●Very low susceptibility to EMI
●Protection according to ISO/TR7637/1 level 4
●Extremely low current consumption < 10µA (with switches open)
●Reverse polarity protection
●Three control inputs: left, right and hazard warning
Description
The Atmel® integrated circuit U2044B is used in relay-controlled automotive flashers. With
two output stages, each side of the vehicle is controlled separately. A left and a right direc-
tion indicator input with only a small control current makes switch contacts for small loads
possible.
The separate hazard warning input simplifies the construction of the hazard switch. Lamp
outage is indicated by frequency doubling during direction mode. Thanks to extreme low
current consumption the U2044B can be directly connected to the battery.
Atmel U2044B
Dual Output Flasher
DATASHEET
2Atmel U2044B [DATASHEET]
4721D–AUTO–05/12
Figure 1. Block Diagram
+
-
+
-
+
-
-
+
-
+
27.5V
+
-
V
Ref2
V
Ref1
V
S
-81 mV
6
7
8
5
9
GND 101311 3 2 4
47 kΩ
12
V
S
/2
R
9
47 kΩ
R
8
R
Shunt
Contact
12
14
1
V
S
-6V
4.7 µF
82 kΩ
R
1
C
1
220Ω
R
2
Hazard warning
R
3
4.7 kΩ
R
6
R
4
1.2 kΩ
R
10
right
left
1.2 kΩ
R
7
1.2 kΩ
R
5
12
Relay
30
30
30
15
31
12700
30 mΩ
4.7 kΩ
K1
4.7 kΩ
3Atmel U2044B [DATASHEET]
4721D–AUTO–05/12
1. Pin Configuration
Figure 1-1. Pinning SO14
Table 1-1. Pin Description
Pin Symbol Function
1OSC Oscillator
2SIL Start input left
3SIR Start input right
4SIHW Start input hazard warning
5VS VS
6CR1 Control input relay 1
7CR2 Control input relay 2
8LD Lamp failure detection
9VS VS
10 GND IC ground
11 OR1 Output relay 1
12 VS VS
13 OR2 Output relay 2
14 OSC Oscillator
1
2
3
4
14
13
12
11
OSC
SIR
SIHW
OSC
OR2
OR1
SIL
5
6
7
10
9
8
VS
CR1
CR2
GND
LD
U2044B
VS
VS
4Atmel U2044B [DATASHEET]
4721D–AUTO–05/12
2. Functional Description
2.1 Oscillator (Pin 1 and 14)
Flashing frequency, f1, is determined by the R1C1 components as follows (see Figure 1 on page 2):
where C1 ≤47µF
R1 = 6.8 kΩ to 180kΩ
In the case of a lamp outage, the oscillator frequency is switched to the lamp outage frequency f2 with f2 ≈ 2.2 × f1.
Duty cycle in normal flashing mode: 50%
Duty cycle in lamp outage mode: 40% (bright phase)
2.2 Start Input Right and Left (Pin 2 and 3)
Flashing is disabled as long as the input comparator is tied to GND (pull-down resistor R7 or R5). The high-side flasher switch
left or right changes the comparator status and enables the output stage at pin 11 or pin 13. R6 and R4 are protection resistors
for the input stage.
With an open flasher switch the current consumption is only I < 10 µA. The IC is kept in stand-by mode until there is a voltage
drop of V ≈ 6.9V at the pull-down resistor.
Direction mode can only be activated when the ignition switch is in the ON-position as shown in Figure 1 on page 2.
2.3 Start Input Hazard Warning (Pin 4)
In contrast to the direction switches, the hazard input is a low-side type. The pull-up resistor R10 provides the off-state. R3 is a
protection resistor for the input stage. Hazard warning can be activated independent of the ignition switch position.
2.4 Supply Voltage Sense (Pin 5)
This pin supplies the lamp outage comparator at pin 8 and is externally connected to the battery (Kl 30).
2.5 Control Input Relay 1 and 2 (Pin 6 and 7)
The feedback detects the bright phase and the dark phase and enables the oscillator.
2.6 Lamp Outage Detection (Pin 8)
The lamp current is monitored via an external shunt resistor, RShunt and an internal comparator, K1, with its reference voltage of
typically 81mV (VS = 12V). The outage of one lamp out of two lamps is detected according to the following calculation:
Nominal current of 1 lamp: 21W/(VS = 12V): Ilamp = 1.75A
Nominal current of 2 lamps: 2 × 21W/(VS = 12V): Ilamp = 3.5A
We recommend setting the detection threshold in the middle of the current range: Ioutage ≈ 2.7A
Thus the shunt resistor is calculated as:
RShunt = VT (K1)/Ioutage
RShunt = 81mV/2.7 A = 30 mΩ
Comparator K1’s reference voltage is matched to the characteristics of filament lamps (see section “Control Signal Threshold”).
The combination of the shunt resistor and the resistance of the wire harness prevents pin 8 from a too high voltage in the case
of shorted lamps.
f1
1
R1C1
×1.5×
-----------------------------------Hz≈
5Atmel U2044B [DATASHEET]
4721D–AUTO–05/12
2.7 Supply Voltage (Pin 9)
This pin supplies the oscillator, the comparators and the logic parts of the IC.
2.8 GND (Pin 10)
The integrated circuit is protected against transients according to ISO-TR 7637-3 level 3 via resistor R2 to ground (–31). An
integrated protection circuit together with external resistors R2, R3, R4, R6, R8 and R9 limits the current pulses in the IC. The IC is
also protected against reversed battery.
2.9 Control Output Relay 1 and 2 (Pin 11 and 13)
The relay control outputs are high-side drivers with a low saturation voltage and capable of driving a typical automotive relay
with a coil resistance of 60Ω.
2.10 Supply Voltage Power (Pin 12)
This pin supplies the relay drivers connected directly to the battery (Kl 30). It is internally clamped by a 27-V Z-diode.
6Atmel U2044B [DATASHEET]
4721D–AUTO–05/12
3. Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Reference point pin 1
Parameters Symbol Value Unit
Supply voltage, 1 min, pins 5, 9 and 12 VS24 V
Junction temperature Tj150 °C
Ambient temperature range Tamb –40 to +100 °C
Storage temperature range Tstg –55 to +150 °C
4. Thermal Resistance
Parameters Symbol Value Unit
Junction ambient, SO14 RthJA 120 K/W
5. Electrical Characteristics
Typical values under normal operation in application circuit Figure 1 on page 2, VS (+30) = 12V.
Reference point ground (–31), Tamb = 25°C, unless otherwise specified
Parameters Test Conditions Symbol Min. Typ. Max. Unit
Supply voltage range Pins 5, 9, 12 VS818 V
Supply current, switches open Pins 5, 9, 12 IS10 µA
Output current for relay driver Pins 11, 13 IO300 mA
Saturation voltage
RL = 82Ω
VS = 8V
VS = 12V
VO1.0
1.2
V
V
Relay output reverse current Pin 11, 13 IO0.1 mA
Relay coil resistance RL60 Ω
Start delay First bright phase ton 10 ms
Control signal threshold
VS = 9V
VS = 13.5V
VS = 16V
VS
VS
VS
70.6
85.0
93.0
mV
mV
mV
Tolerance of control signal threshold VS = 9V to 16V, pin 8,
Tamb = –140°C to 100°C –6 +6 %
Temperature coefficient of control
signal threshold VS = 13.5V, pin 8 TK10 µV/K
Clamping voltage Tamb = –40°C to 100°C V12 25.0 27.5 30.0 V
Relay output overvoltage detection
(relay disabled) Tamb = –40°C to 100°C V12 18 20 22 V
7Atmel U2044B [DATASHEET]
4721D–AUTO–05/12
6. Tolerances
Typical values under normal operation in application circuit Figure 1 on page 2, VS (+30) = 12V.
Reference point ground (–31), Tamb = 25°C, unless otherwise specified
Parameters Test Conditions Symbol Min. Typ. Max. Unit
Frequency determining resistor R16.8 510 kΩ
Frequency determining capacitor C147 µF
Frequency tolerance
Normal flashing, basic frequency f1 not
including the tolerance of the external
components R1 and C1
Δf1–5 +5 %
Bright period Basic frequency f1Δf147 53 %
Control frequency f2Δf237 45 %
Frequency increase Lamp failure f22.15 ×f12.3 ×f1Hz
Lamp load PL1 W
8Atmel U2044B [DATASHEET]
4721D–AUTO–05/12
8. Package Information
7. Ordering Information
Extended Type Number Package Remarks
U2044B-MFPY SO14 Tubed, Pb-free
U2044B-MFPG3Y SO14 Taped and reeled, Pb-free
Package Drawing Contact:
packagedrawings@atmel.com
GPC DRAWING NO.
REV. TITLE
6.541-5053.01-4 1
04/13/12
Package: SO14
COMMON DIMENSIONS
(Unit of Measure = mm)
MIN NOM MAXSymbol
Dimensions in mm
specifications
according to DIN
technical drawings
0.18 0.250.10A1
8.65 8.758.55D1)
Note1): Dimensions “D” and “E1” do not include Moldflash or protrusion.
(MAX. 0.15mm per side)
Bemerkung: ASE
6.00 6.205.80E
0.84 1.270.40L
1.27 BSC
e
3.90 4.003.80E1)
0.22 0.250.19C
0.42 0.510.33b
1.38 1.501.25A2
1.55 1.751.35A
17
14 8
E
E1
L
C
D
b
e
A
A2
A1
9Atmel U2044B [DATASHEET]
4721D–AUTO–05/12
9. Revision History
Please note that the following page numbers referred to in this section refer to the specific revision mentioned, not to this
document.
Revision No. History
4721D-AUTO-05/12 • Section 8 “Package Information” on page 8 changed
4721C-AUTO-02/08
• Put datasheet in the newest template
• Pb-free logo on page 1 deleted
• Figure title Figure 2-1 on page 3 renamed
• Section 5 “Thermal Resistance” on page 6 changed
• Section 8 “Ordering Information” on page 7 changed
• Section 9 “Package Information” on page 7 changed
4721B-AUTO-09/05
• Put datasheet in the newest template
• Pb-free logo on page 1 added
• New heading rows in Table “Absolute Maximum Rating” on page 6 added
• Ordering Information on page 7 changed
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