6.2.2.9 16-MHz Crystal

The TPS659037 device has the ability to accept a 16-MHz crystal input. Providing the 16-MHz crystal input to the device allows the output of a stable and accurate 32-kHz clock to be used by the applications processor. The crystal input is divided down by 500 internally to produce the 32-kHz output clock. The crystal should be connected to the TPS659037 device as shown in Figure 6-6.

Figure 6-6 Crystal Input Configuration

As shown in Figure 6-6, the OSC16MCAP pin requires a 2.2-µF 6.3-V filtering capacitor near the pin. Also, the crystal requires between 9 pF and 11 pF of load capacitance on both pins. To meet this requirement, using two 10-pF capacitors is recommended. See Table 6-2 for the specific load capacitors that are recommended.

The 16-MHz crystal is not required for operation of the TPS659037 device. The OSC16M_CFG OTP bit can be set to disable the 16MHz crystal completely, and enable one of the following two alternative options for system clock generation:

• A 32-kHz square wave can be supplied to the OSC16MIN pin. This option is typically used in applications where the processor requires an accurate system clock and there is one already available in the system. In that case, the available 32-kHz clock can be provided to the PMIC and added to the boot sequence as an output. In this configuration, the OSC16MOUT and OSC16MCAP pins can be left floating, and the internal 16-MHz oscillator is bypassed. Bypassing the 16-MHz oscillator results in a lower quiescent current.
• If the application does not require an accurate system clock for the processor, then providing one to the PMIC is not required. This option produces a lower quiescent current as seen in Section 4. In this configuration, the OSC16MIN pin should be grounded, while the OSC16MOUT and OSCMCAP pins can be left floating. Lastly, the GATE_RESET_OUT OTP bit should be used to allow the TPS659037 device to power up without the presence of the 16.384-MHz crystal nor the 32-kHz clock input.

Please note that if the OSC16M_CFG OTP bit is set to 0, a 16-MHz crystal must be present for the proper operation of the device.