MAX31334 Evaluation Kit

Evaluates: MAX31334

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Detailed Description

The MAX31334 is an ultra-low power, real-time clock (RTC) time-keeping device that consumes a nominal 70nA

timekeeping current, extending battery life. It features an integrated high-side power pass switch that enables ultra-low-

power idle modes on duty-cycled applications by disconnecting power to other devices on the system. The MAX31334

supports a wide range of 32.768kHz crystals. Crystals with any capacitive loading (CL) spec can be used, which broadens

the pool of usable crystals for this device. This device is accessed through an I2C serial interface. The device also features

a backup supply (VBAT) and automatically switches over to the backup supply (VBAT) when the main supply (VCC) drops

below the programmed threshold voltage and the backup supply (VBAT) voltage.

Other features include two time-of-day alarms, interrupt outputs, a programmable square-wave output, event detection

input with timestamping, and a serial bus timeout mechanism. The 32-byte timestamp registers double as RAM storage.

The device features a digital Schmitt trigger input (DIN) which can be used to record timestamps and/or generate an

interrupt on the falling/rising edge of the DIN signal. The clock/calendar provides seconds, minutes, hours, day, month,

year, and date information. A 1/128 second register is available for a sub-second timestamp resolution. The date at the

end of the month is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The

clock operates in a 24-hour/12-hour format.

Functional Test Procedure

Current Draw at Time-Keeping Operation

1. To measure the current drawn under normal Real-Time Clock conditions without any interrupt or clock input/output,

do the following:

a. In the RTC Configuration section, click the Read button.

b. Disable CLKOUT.

c. Select 1Hz for Frequency.

2. For WLP version (U1), remove the jumper from JU7 and connect the pico ammeter between pin 1 and pin 2 of JU7.

3. In the Registers tab under the Register Map section, click the Read button and ensure that the value of register 0x03

(RTC_Config1) shows 0x01. Otherwise, set it to 0x01 and click the Write button. Now the reading in the picometer is

the current from MAX31334 only. It should be around 70nA.

NOTE: All instruments need to be disconnected from the I/O ports of the IC, since any loading would add current

consumption.

4. Remove pico ammeter and replace the jumper on JU7 (for WLP version)

Setting the Clock

In the Configuration & Time tab in the Date/Time Configuration section, enter the start point of the date and time and

then click Set. The clock starts to count from the set point after the Status Log shows “Write successful”. In the Real

Time Monitoring section, verify that the clock is counting from the written start date and time.

Clock Output Measurement

In the Configuration & Time tab in the RTC Configuration section, enable CLKOUT and select the desired CLKOUT

frequency. The clock output can be monitored using an oscilloscope connected to INTB/CLKOUT. A frequency counter

can also be used to measure the clock frequency accurately. Refer to the Oscillator Circuit and Clock Accuracy section

in the MAX31334 data sheet to correct any clock accuracy error.

Alarm Interrupt Output

On the Alarms & Timer tab in the Alarm 1 Configuration section, select the Repetition Rate to set the alarm scenario.

In the Interrupts subsection of the Interrupts & Flags section, check the Alarm 1 Interrupt box. In the Flags subsection,

click the Read button twice to clear the alarm flag bit if it has been previously set. When the RTC reaches the alarm time

set in Alarm 1 Configuration, the alarm output at INTB goes from high to low. It changes to high again by clicking the

Read button in the Flags subsection. The interrupt status can also be checked by clicking the Read button in the Flags

subsection. Repeat the same steps for Alarm 2, but measure the alarm interrupt output at INTA.

Note: Both Alarm 1 and Alarm 2 can be output on INTA when CLKOUT is enabled.