Cypress CY25819 manual Level Digital Inputs, Modulation Rate, Maximum Ratings 1, CY25818/19

CY25818/19

3-Level Digital Inputs

S0 digital input is designed to sense three logic levels desig- nated as HIGH “1,” LOW “0,” and MIDDLE “M.” With this 3-Level digital input logic, the 3-Level logic is able to detect three different logic levels.

The S0 pin includes an on-chip 20K (10K/10K) resistor divider. No external application resistors are needed to implement 3-Level logic, as follows.

Logic Level “0”: 3-Level logic pin connected to GND.

Logic Level “M”: 3-Level logic pin left floating (no connection.)

Logic Level “1”: 3-Level logic pin connected to Vdd. Figure 1 illustrates how to implement 3-Level Logic.

LO G IC	LO G IC	LO G IC
LO W (0)	M ID D LE (M )	H IG H (H )
			V D D
S 0	S0	S 0
to VSS	U N C O NN EC TED	to V DD

Modulation Rate

Spread Spectrum Clock Generators utilize frequency modulation (FM) to distribute energy over a specific band of frequencies. The maximum frequency of the clock (fmax) and minimum frequency of the clock (fmin) determine this band of frequencies. The time required to transition from fmin to fmax and back to fmin is the period of the Modulation Rate, Tmod. The Modulation Rates of SSCG clocks are generally referred to in terms of frequency, and fmod = 1/Tmod.

The input clock frequency, fin, and the internal divider determine the Modulation Rate.

In the case of CY25818/19 devices, the (Spread Spectrum) Modulation Rate, fmod, is given by the following formula:

fmod = fIN/DR

where fmod is the Modulation Rate, fIN is the Input Frequency, and DR is the Divider Ratio, as given in Table 3.

V S S

Figure 1. 3-Level Logic

Table 3. Modulation Rate Divider Ratios

Product		Input Frequency Range				Divider Ratio (DR)
CY25818		8–16 MHz					256
CY25819		16–32 MHz					512
Maximum Ratings[1, 2]			Input Voltage Relative to Vss:						Vss + 0.3V
Supply Voltage (Vdd):		+ 5.5V	Operating Temperature:					0°C to + 70°C
			Storage Temperature:					–65°C to + 150°C
Input Voltage Relative to Vdd:		Vdd + 0.3V
Table 4. DC Electrical Characteristics Vdd = 3.3V ±10%, TA = 0°C to +70°C and CL = 15 pF (unless otherwise noted)
Parameter	Description	Conditions			Min.	Typ.		Max.		Unit
Vdd	Power Supply Range			2.97		3.3		3.63		V
VINH	Input HIGH Voltage	S0 Input		0.85 Vdd		Vdd		Vdd		V
VINM	Input MIDDLE Voltage	S0 Input		0.40 Vdd		0.50 Vdd		0.60 Vdd		V
VINL	Input LOW Voltage	S0 Input		0.0		0.0		0.15 Vdd		V
VOH1	Output HIGH Voltage	IOH = 4 ma, SSCLK and REFCLK		2.4		–		–		V
VOH2	Output HIGH Voltage	IOH = 6 ma, SSCLK and REFCLK		2.0		–		–		V
VOL1	Output LOW Voltage	IOL = 4 ma, SSCLK Output			–	–		0.4		V
VOL2	Output LOW Voltage	IOL = 10 ma, SSCLK Output			–	–		1.2		V
CIN1	Input Capacitance	XIN (Pin 1) and XOUT (Pin 8)		6.0		7.5		9.0		pF
CIN2	Input Capacitance	All Digital Inputs		3.5		4.5		6.0		pF
IDD1	Power Supply Current	FIN=8 MHz, no load			–	10.0		12.5		mA
IDD3	Power Supply Current	FIN=32 MHz, no load			–	19.0		23.0		mA
IDD4	Power Supply Current	PD# = Vss			–	150		250		mA

Document #: 38-07362 Rev. *B Page 3 of 7

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