55.18 DFLL48M Electrical Specifications

Table 55-22. Digital Frequency Locked Loop (DFLL48M) Electrical Specifications
AC CHARACTERISTICSStandard Operating Conditions: VDD = AVDD = 1.71V to 3.63V (unless otherwise stated)

Operating temperature:

-40°C ≤ TA ≤ +85°C for Industrial Temperature

Param. No.SymbolCharacteristicsMin.Typ.Max.UnitsConditions
DFLL48M (Open Loop) (1,2)
DFLL_1DFLL_OL_FOUTDFLL Open Loop Clock Frequency45.84849.3MHzLDO Mode
DFLL_9DFLL_OL_SRTStart-Up (Ready bit valid)——7µsLDO Mode

FOUT within 90% of final value

DFLL48M (Closed Loop) (1,3,4,6)
DFLL_11DFLL_CL_FINDFLL Closed loop Input Frequency Range 7323276833000HzLDO Mode
DFLL_13DFLL_CL_FOUTDFLL Closed Loop Clock Frequency—47.972—MHzLDO Mode

XOSC32 32.768kHz PPM≤100,

DFLLMUL = 1464

DFLL_15DFLL_CL_JitterDFLL Period Jitter Pk-to-Pk——2% LDO Mode

XOSC32 32.768kHz PPM≤100,

DFLLMUL = 1464

DFLL_21DFLL_CL_SRT (5)DFLL Closed Loop Mode / Lock Time——1145µsLDO Mode

XOSC32 32.768kHz PPM≤100,

DFLLMUL = 1464

Note:
  1. DFLL48 in open or close loop can be used only with LDO regulator.
  2. Not recommended for functional USB operation, SOF sync start-up only.
  3. In Closed loop mode the DFLL can use a variety of clock sources. The DFLL can be trimmed using register DFLLMUL.
  4. To ensure that the device stays within the maximum allowed clock frequency, any reference clock for DFLL in close loop must be within a 2% error accuracy.
  5. DFLLMUL = 1464, DFLLCTRL.BPLCKC = 1: only fine value change, coarse value locked to the reset value.

    DFLLCTRL.QLDIS = 0: quick lock enable,

    DFLLCTRL.CCDIS = 1: Enabling chill cycles might double the lock time.

    DFLLMUL.FSTEP = 10 : Max fine step size, divided or dividing into two parts, search. 10 is a optimum value.

  6. During a maximum 30 cycles of the reference clock period, between lock flag asserted and frequency stabilization, DFLL accuracy will be limited.

    To minimize the cycle-to-cycle jitter during lock search, in addition to selecting a low step value (DFLLMUL.FSTEP, DFLLMUL.CSTEP), it is recommended to disable the Quick Lock feature.