The LP87524B/J/P-Q1 device contains a CLKIN input to synchronize switching clock of the buck regulator with the external clock. The block diagram of the clocking and PLL module is shown in Figure 7. Depending on the PLL_MODE[1:0] bits (in PLL_CTRL register) and the external clock availability, the external clock is selected and interrupt is generated as shown in Table 2. The interrupt can be masked with SYNC_CLK_MASK bit in TOP_MASK1 register. The nominal frequency of the external input clock is set by EXT_CLK_FREQ[4:0] bits (in PLL_CTRL register) and it can be from 1 MHz to 24 MHz with 1-MHz steps. The external clock must be inside accuracy limits (–30%/+10%) for valid clock detection.
The NO_SYNC_CLK interrupt (in INT_TOP1 register) is also generated in cases the external clock is expected but it is not available. These cases are start-up (read OTP-to-STANDBY transition) when PLL_MODE[1:0] = 01 and regulator enable (STANDBY-to-ACTIVE transition) when PLL_MODE[1:0] = 10.
|DEVICE OPERATION MODE||PLL_MODE[1:0]||PLL AND CLOCK DETECTOR STATE||INTERRUPT FOR EXTERNAL CLOCK||CLOCK|
|STANDBY||01||Enabled||When external clock appears or disappears||Automatic change to external clock when available|
|ACTIVE||01||Enabled||When external clock appears or disappears||Automatic change to external clock when available|
|ACTIVE||10||Enabled||When external clock appears or disappears||Automatic change to external clock when available|