U5020M ATMEL | Alldatasheet
Document overview
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Technical content
Features
Low Current Consumption: IDD < 100 µA RC Oscillator Internal Reset During Power-up and Supply Voltage Drops (POR) “Short” Trigger Window for Active Mode “Long” Trigger Window for Sleep Mode Cyclical Wake-up of the Microcontroller in Sleep Mode Trigger Input Six Wake-up Inputs Reset Output Enable Output
Description
The digital window watchdog timer, U5020M, is a CMOS integrated circuit. In applica- tions where safety is critical, it is especia lly important to monitor the microcontroller. Normal microcontroller operation is indicated by a cyclically transmitted trigger signal, which is received by a window watchdog timer within a defined time window. A missing or a wrong trigger signal causes the watchdog timer to reset the microcon- troller. The IC is tailored for microcontrollers which can work in both full-power and sleep mode. With an additional voltage monitoring (power-on reset and supply voltage drop reset), the U5020M offers a complete monitoring solution for microsystems in automotive and industrial applications. Digital Window Watchdog Timer U5020M
2 U5020M
Figure 1. Block Diagram with External Ciruit Figure 2. Pinning SO16
4755A–AUTO–11/03 Functional Supply, Pin 13 The U5020M requires a stabilized supply voltage VDD = 5 V ±5% to comply with its elec- trical characteristics. An external buffer capacitor of C = 10 nF may be connected between pin 13 and GND. RC Oscillator, Pin 15 The clock frequency, f, can be adjusted by the components R 1 and C1 according to the formula: where t = 1.35 + 1.57 R1 (C1 + 0.01) R1 in k/g87, C1 in nF and t in µs The clock frequency determines all time periods of the logic part as shown in the table “Electrical Characteristics” under the subheading “Timing” on page 8. With an appropri- ate component selection, the clock frequency, f, is nearly independent of the supply voltage as shown in Figure 3 on page 4. Frequency tolerance /g68fmax = 10% with R1 ±1%, C1 = ±5% Pin Description Pin Symbol Function
1 TM Test must not be connected
2 TM Test must be connected to GND
Wake-up inputs (pull-down resistor) There are six digitally debounced wake-up inputs. During the long trigger mode each signal slope at the inputs initiates a reset pulse at pin 10. 9E N A Enable output (push-pull) It is used for the control of peripheral components. It is activated after the processor triggers three times correctly.
10 RESET
Reset output (open drain) Resets the processor in the case of a trigger error or if a wake-up pulse occurs during the long watchdog period.
11 TRIG Trigger input (pull-up resistor)
It is connected to the microprocessor’s trigger signal.
12 MODE Mode input (pull-up resistor)
The processor’s mode signal initiates the switchover between the long and the short watchdog time.
13 VDD Supply voltage
14 GND Ground, reference voltage
15 OSC RC oscillator
16 TS Time switch input
Programming pin to select different time durations for the long watchdog time. f 1 t---=
4 U5020M
Figure 3. Period t versus R1, at C1 = 500 pF Figure 4. Power-up Reset and Mode Switchover troller in its defined reset status (see Figure 4). Pin 10 has an open-drain output.
- If the low signal does not occur within t1, (see Fig-
ure 4) the watchdog generates a reset pulse, t 6, and the time, t 1, starts again. time a reset pulse is generated.
6 U5020M
Figure 6. Pulse Diagram of a Correct Trigger Sequence During the Short Watchdog Time signal during the enable time, t5, activates a reset pulse, t6. low potential at the mode pin (pin 12). Figure 7. Pulse Diagram of the Long Watchdog Time
4755A–AUTO–11/03 Application Hint In order to prevent the IC from an undesired reset output signal which may be caused by transcients on the supply under certain conditions, a PC board connection from pin 2 to GND is strongly recommended. 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. Parameters Symbol Value Unit Supply voltage V DD 6.5 V Output current I OUT ±2 mA Input voltage V IN -0.5 V to VDD + 0.5 V V Ambient temperature range T amb -40 to +85 /g176C Storage temperature range T stg -55 to +150 /g176C Thermal Resistance Parameters Symbol Value Unit Junction ambient SO16 R thJA 160 K/W
8 U5020M
4755A–AUTO–11/03
Electrical Characteristics
VDD = 5 V; Tamb = -40°C to +85°C; reference point is ground (pin14); Figure 4 on page 4, unless otherwise specified Parameters Test Conditions Pin Symbol Min. Typ. Max. Unit Supply voltage 13 V DD 4.5 5.5 V Current consumption R 1 = 66 k/g87 13 I DD 100 µA Power-on reset Logic functions 13 V DD 1V Power-on reset Threshold 13 V POR 3.8 V Power-on reset Hysteresis 13 V hys 100 mV Inputs 3 to 8, 11, 12, 16 Upper threshold (“1”) V IH 4.0 V Lower threshold (“0”) V IL 1.0 V Input voltage range V IN -0.4 VDD + 0.2 V Input current Depending on pin I IN -20 20 µA Output Pin 9 Maximum output current I OUT 2m A Upper output voltage (“1”) I OUT = 1 mA V OH 4.5 V Lower output voltage (“0”) I OUT = -1 mA V OL 0.5 V Output Pin 10 Maximum output current I OUT 2m A Lower output voltage (“0”) I OUT = -1 mA V OL 0.5 V Timing Debounce period Trig, Mode 11, 12 3 4 cycle Debounce period Wake-up 1-6 3 to 8 96 128 cycle Maximum trigger pulse period 45 cycle Power-up reset time t o 201 cycle Time-out period t1 1,112 cycle Short disable time t 2 130 cycle Short enable time t 3 124 cycle Long disable time Input switch = low (0) 16 t 4 71,970 cycle Long enable time Input switch = low (0) 16 t 5 30,002 cycle Long disable time Input switch = high (1) 16 t 4 1,200 cycle Long enable time Input switch = high (1) 16 t 5 400 cycle Reset-out time t6 40 cycle
4755A–AUTO–11/03
Package Information
Ordering Information
Extended Type Number Package Remarks U5020M-FP SO16 – technical drawings according to DIN specifications Dimensions in mm 10.0 9.85 8.89 0.4 1.27 1.4 0.25 0.10 5.2 4.8 3.7 3.8 6.15 5.85 0.2 16 9
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