AB08X5

AB08X5 ABRACON

Document overview

• PDF pages: 33

Technical content

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Features

• Ultra-low supply current (all at 3V): - 14 nA with RC oscillator - 22 nA with RC oscillator and Autocalibration - 55 nA with crystal oscillator
• Baseline timekeeping features: - 32.768 kHz crystal oscillator with integrated load capacitor/resistor
• Counters for hundredths, seconds, minutes, hours, date, month, year, century, and weekday - Alarm capability on all counters - Programmable output clock generation (32.768 kHz to 1 year) - Countdown timer with repeat function - Automatic leap year calculation
• Advanced timekeeping features: - Integrated power optimized RC oscillator - Advanced crystal calibration to ± 2 ppm - Advanced RC calibration to ± 16 ppm - Automatic calibration of RC oscillator to crystal oscillator
• Watchdog timer with hardware reset - 256 bytes of general purpose RAM
• Power management features: - Automatic switchover to VBAT - External interrupt monitor - Programmable low battery detection threshold - Programmable analog voltage comparator
• I2C (up to 400 kHz) and 3-wire or 4-wire SPI (up to 2 MHz) serial interfaces available
• Operating voltage 1.5-3.6 V
• Clock and RAM retention voltage 1.5-3.6 V
• Operating temperature –40 to 85 °C
• All inputs include Schmitt Triggers
• 3x3 mm QFN-16 package

Applications

• Smart cards
• Wireless sensors and tags
• Medical electronics
• Utility meters
• Data loggers
• Appliances
• Handsets
• Consumer electronics
• Communications equipment

Description

The ABRACON AB08X5 Real-Time Clock family provides a groundbreaking combination of ultra-low power coupled with a highly sophisticated feature set. With power requirements significantly lower than any other industry RTC (as low as 14 nA), these are the first semiconductors based on innovative SPOTTM (Subthreshold Power Optimized Technology) CMOS platform. The AB08X5 includes on-chip oscillators to provide minimum power consumption, full RTC functions including battery backup and programmable counters and alarms for timer and watchdog functions, and either an I2C or SPI serial interface for communication with a host controller.

Disclaimer: AB08X5 series of devices are based on innovative SPOT technology, proprietary to Ambiq Micro.

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1. Family Summary

The AB08X5 family consists of several members (see Table 1). All devices are supplied in a standard 3x3 mm QFN-16 package. Members of the software and pin compatible AB18X5 RTC family are also listed.

Table 1: Family Summary

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2. Functional Description

Figure 1 illustrates the AB08X5 functional design.

Figure 1. Detailed Block Diagram

The AB08X5 serves as a full function RTC for host processors such as microcontrollers. The AB08X5 includes 3 distinct feature groups: 1) baseline timekeeping features, 2) advanced timekeeping features, and 3) basic power management features. Functions from each feature group may be controlled via I/O offset mapped registers. These registers are accessed using either an I2C serial interface (e.g., in the AB0805) or a SPI serial interface (e.g., in the AB0815). Each feature group is described briefly below and in greater detail in subsequent sections.

The baseline timekeeping feature group supports the standard 32.786 kHz crystal (XT) oscillation mode for maximum frequency accuracy with an ultra-low current draw of 55 nA. The baseline timekeeping feature group also includes a standard set of counters monitoring hundredths of a second up through centuries. A complement of countdown timers and alarms may additionally be set to initiate interrupts or resets on several of the outputs.

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The advanced timekeeping feature group supports two additional oscillation modes: 1) RC oscillator mode, and 2) Autocalibration mode. At only 14 nA, the temperature-compensated RC oscillator mode provides an even lower current draw than the XT oscillator for applications with reduced frequency accuracy requirements. A proprietary calibration algorithm allows the AB08X5 to digitally tune the RC oscillator frequency and the XT oscillator frequency with accuracy as low as 2 ppm at a given temperature. In Autocalibration mode, the RC oscillator is used as the primary oscillation source and is periodically calibrated against the XT oscillator. Autocalibration may be done automatically every 8.5 minutes or 17

minutes and may also be initiated via software. This mode enables average current draw of only 22 nA with frequency accuracy similar to the XT oscillator. The advanced timekeeping feature group also includes a rich set of input and output configuration options that enables the monitoring of external interrupts (e.g., pushbutton signals), the generation of clock outputs, and watchdog timer functionality.

Power management features built into the AB08X5 enable it to operate as a backup device in both linepowered and battery-powered systems. An integrated power control module automatically detects when main power (VCC) falls below a threshold and switches to backup power (VBAT). 256B of ultra-low leakage RAM enable the storage of key parameters when operating on backup power. The AB08X5 also includes digitally-tunable voltage detection on the backup power supply.

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3. AB08X5 Example Applications

3.1 Battery Backed Up RTC

The most common AB08X5 application is a battery backed up RTC, which maintains time and may hold data in RAM. The AB08X5 is normally powered from a system power supply, which may be a larger battery. The AB08X5 is continuously charging a supercapacitor or rechargeable battery via the internal trickle charger. When the main power supply goes away, the AB08X5 automatically switches to the VBAT supply and maintains time and RAM data at very low battery supply currents.

3.2 RTC with Interrupt Aggregation

The flexible inputs of the AB08X5 can be used to aggregate a variety of interrupt sources, including external digital inputs, analog levels, timers and alarms into a single interrupt source to an MCU.

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4. Package Pins

4.1 Pin Configuration and Connections

Figure 2 and Table 2 show the QFN-16 pin configurations for the AB08X5 parts. Pins labeled NC must be left unconnected. The thermal pad, pin 17, on the QFN-16 packages must be connected to VSS.

Figure 2. Pin Configuration Diagram

Table 2: Pin Connections

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4.2 Pin Descriptions

Table 3 provides a description of the pin connections.

Table 3: Pin Descriptions

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Table 3: Pin Descriptions

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5. Electrical Specifications

5.1 Absolute Maximum Ratings

Table 4 lists the absolute maximum ratings.

Table 4: Absolute Maximum Ratings

5.2 Power Supply Parameters

Figure 3 and Table 5 describe the power supply and switchover parameters. See Power Control and Switching for a detailed description of the operations.

Power State

Figure 3. Power Supply Switchover

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

For Table 5, TA = -40 °C to 85 °C, TYP values at 25 °C.

Table 5: Power Supply and Switchover Parameters

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5.3 Operating Parameters

Table 6 lists the operating parameters.



For Table 6, TA = -40 °C to 85 °C, TYP values at 25 °C.

Table 6: Operating Parameters

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5.4 Oscillator Parameters

Table 7 lists the oscillator parameters.

 VCC = 1.7 to 3.6V, TYP values at 25 °C and 3.0V.

For Table 7, TA = -40 °C to 85 °C unless otherwise indicated.

Table 7: Oscillator Parameters

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Figure 4 shows the typical calibrated RC oscillator frequency variation vs. temperature. RC oscillator calibrated at 2.8V, 25°C.

Figure 4. Calibrated RC Oscillator Typical Frequency Variation vs. Temperature

Figure 5 shows the typical uncalibrated RC oscillator frequency variation vs. temperature.

Figure 5. Uncalibrated RC Oscillator Typical Frequency Variation vs. Temperature

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5.5 VCC Supply Current

Table 8 lists the current supplied into the VCC power input under various conditions.

 TYP values at 25 °C, MAX values at 85 °C, VCC Power state

For Table 8, TA = -40 °C to 85 °C, VBAT = 0 V to 3.6 V

Table 8: VCC Supply Current

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Figure 6 shows the typical VCC power state operating current vs. temperature in XT mode.

Figure 6. Typical VCC Current vs. Temperature in XT Mode

Figure 7 shows the typical VCC power state operating current vs. temperature in RC mode.

Figure 7. Typical VCC Current vs. Temperature in RC Mode

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Figure 8 shows the typical VCC power state operating current vs. temperature in RC Autocalibration mode.

Figure 8. Typical VCC Current vs. Temperature in RC Autocalibration Mode

Figure 9 shows the typical VCC power state operating current vs. voltage for XT Oscillator and RC Oscillator modes and the average current in RC Autocalibrated mode.

Figure 9. Typical VCC Current vs. Voltage, Different Modes of Operation

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Figure 10 shows the typical VCC power state operating current during continuous I2C and SPI burst read and write activity. Test conditions: TA = 25 °C, 0x55 data pattern, 25 s between each data byte, 20 pF load on each bus pin, pull-up resistor current not included.

Figure 10. Typical VCC Current vs. Voltage, I²C and SPI Burst Read/Write

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5.6 VBAT Supply Current

Table 9 lists the current supplied into the VBAT power input under various conditions.



For Table 9, TA = -40 °C to 85 °C, TYP values at 25 °C, MAX values at 85 °C, VBAT Power state.

Table 9: VBAT Supply Current

Figure 11 shows the typical VBAT power state operating current vs. temperature in XT mode.

Figure 11. Typical VBAT Current vs. Temperature in XT Mode

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Figure 12 shows the typical VBAT power state operating current vs. temperature in RC mode.

Figure 12. Typical VBAT Current vs. Temperature in RC Mode

Figure 13 shows the typical VBAT power state operating current vs. temperature in RC Autocalibration mode.

Figure 13. Typical VBAT Current vs. Temperature in RC Autocalibration Mode

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Figure 14 shows the typical VBAT power state operating current vs. voltage for XT Oscillator and RC Oscillator modes and the average current in RC Autocalibrated mode, VCC = 0 V.

Figure 14. Typical VBAT Current vs. Voltage, Different Modes of Operation

Figure 15 shows the typical VBAT current when operating in the VCC power state, VCC = 1.7 V.

Figure 15. Typical VBAT Current vs. Voltage in VCC Power State

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5.7 BREF Electrical Characteristics

Table 10 lists the parameters of the VBAT voltage thresholds. BREF values other than those listed in the table are not supported.



For Table 10, TA = -20 °C to 70 °C, TYP values at 25 °C, VCC = 1.7 to 3.6V.

Table 10: BREF Parameters

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5.8 I²C AC Electrical Characteristics

Figure 16 and Table 11 describe the I2C AC electrical parameters.

Figure 16. I²C AC Parameter Definitions



For Table 11, TA = -40 °C to 85 °C, TYP values at 25 °C.

Table 11: I²C AC Electrical Parameters

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5.9 SPI AC Electrical Characteristics

Figure 17, Figure 18, and Table 12 describe the SPI AC electrical parameters.

Figure 17. SPI AC Parameter Definitions – Input

Figure 18. SPI AC Parameter Definitions – Output

 For Table 12, TA = -40 °C to 85 °C, TYP values at 25 °C.

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Table 12: SPI AC Electrical Parameters

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5.10 Power On AC Electrical Characteristics

Figure 19 and Table 13 describe the power on AC electrical characteristics for the FOUT pin and XT oscillator.

Figure 19. Power On AC Electrical Characteristics



For Table 13, TA = -40 °C to 85 °C, VBAT < 1.2 V

Table 13: Power On AC Electrical Parameters

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6. Tape and Reel Information

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Table 14: Tape and Reel Dimensions

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7. Reflow Profile

Figure 20 illustrates the reflow soldering requirements.

Figure 20. Reflow Soldering Diagram

Table 15: Reflow Soldering Requirements (Pb-free assembly)

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8. Ordering Information

Table 16: Ordering Information

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9. Notes

i. The parts are manufactured in accordance with this specification. If other conditions and specifications which are required for this specification, please contact ABRACON for more information. ii. ABRACON will supply the parts in accordance with this specification unless we receive a written request to modify prior to an order placement. iii. In no case shall ABRACON be liable for any product failure from inappropriate handling or operation of the item beyond the scope of this specification. iv. When changing your production process, please notify ABRACON immediately. v. ABRACON Corporation’s products are COTS – Commercial-Off-The-Shelf products; suitable for

Commercial, Industrial and, where designated, Automotive Applications. ABRACON’s products are not specifically designed for Military, Aviation, Aerospace, Life-dependant Medical applications or any application requiring high reliability where component failure could result in loss of life and/or property. For applications requiring high reliability and/or presenting an extreme operating environment, written consent and authorization from ABRACON Corporation is required. Please contact ABRACON Corporation for more information. vi. All specifications and Marking will be subject to change without notice.

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