SPC574S60 datasheet(49/77 Pages) STMICROELECTRONICS

49 / 77 page

DS10601 Rev 6

49/77

SPC574Sx

Electrical characteristics

Oscillator Transconductance

(3.3 V)

TJ =-40 °C

to 150 °C

fXTAL ≤ 8 MHz

2.2

12.1

mA/V

DfXTAL ≤ 20 MHz

28.6

DfXTAL ≤ 40 MHz

9.7

37.4

Oscillator Transconductance

(5 V)

TJ =-40 °C

to 150 °C

fXTAL ≤ 8 MHz

2.6

11.0

mA/V

DfXTAL ≤ 20 MHz

7.9

26.0

DfXTAL ≤ 40 MHz

10.4

34.0

VEXTAL

Oscillation Amplitude on the

EXTAL pin after startup(9)

TJ = –40 °C to 150 °C

0.5

1.6

VHYS

D Comparator Hysteresis

TJ = 150 °C

0.1

1.0

IXTAL

D XTAL current(10)

TJ = 150 °C

—

1. All oscillator specifications are valid for VDD_HV_IO =3.0 V – 5.5V.

2. The range is selectable by UTEST miscellaneous DCF clients XOSC_LF_EN and XOSC_EN_40MHZ.

3. This value is determined by the crystal manufacturer and board design.

4. Proper PC board layout procedures must be followed to achieve specifications.

5. Crystal recovery time is the time for the oscillator to settle to the correct frequency after adjustment of the integrated load

capacitor value.

6. This parameter is guaranteed by design rather than 100% tested.

7. Applies to an external clock input and not to crystal mode.

8. See crystal manufacturer’s specification for recommended load capacitor (CL) values.The external oscillator requires

external load capacitors when operating from 8 MHz to 16 MHz. Account for on-chip stray capacitance (CS_EXTAL/CS_XTAL)

and PCB capacitance when selecting a load capacitor value. When operating at 20 MHz/40 MHz, the integrated load

capacitor value is selected via S/W to match the crystal manufacturer’s specification, while accounting for on-chip and PCB

capacitance.

9. Amplitude on the EXTAL pin after startup is determined by the ALC block, i.e., the Automatic Level Control Circuit. The

function of the ALC is to provide high drive current during oscillator startup, but reduce current after oscillation in order to

reduce power, distortion, and RFI, and to avoid over-driving the crystal. The operating point of the ALC is dependent on the

crystal value and loading conditions.

10. IXTAL is the oscillator bias current out of the XTAL pin with both EXTAL and XTAL pins grounded. This is the maximum

current during startup of the oscillator. The current after oscillation is typically in the 2-3 mA range and is dependent on the

load and series resistance of the crystal. Test circuit is shown in Figure 12. The ALC block is the Automatic Level Control

Circuit. The function of the ALC is to provide high drive current during oscillator startup, but reduce current after oscillation

in order to reduce power, distortion, and RFI, and to avoid overdriving the crystal.

Table 32. External Oscillator electrical specifications(1) (continued)

Symbol

Parameter

Conditions

Value

Unit

Min

Max

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