RC19302A00AGNT#BD0 datasheet(48/62 Pages) RENESAS

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R31DS0210EU0106 Rev.1.06

Page 48

May 11, 2026

RC193xx Datasheet

Table 34 contains values for the items in Figure 20 and Figure 21.

5.4

Power Down Tolerant Pins

Pins labeled Power Down Tolerant (PDT) can be driven by voltages as high as the normal VDD of the chip, even

though VDD is not present (the device is not powered). There will be no ill effects to the device and it will power up

normally. This feature supports disaggregation, where the RC193xx may be on one circuit board and devices that

interface with it are on other boards. These boards may power up at different times, driving pins on the RC193xx

before it has received power. NOTE: The differential CLKIN pins are limited to 1.4V. Applying a voltage higher

than this may damage the part.

5.5

Flexible Startup Sequencing

RC193xx devices support Flexible Startup Sequencing (FSS). FSS allows application of CLKIN at different times

in the device/system startup sequence. FSS is an additional feature that helps the system designer manage the

impact of disaggregation. Table 35 shows the supported sequences; that is, the RC193xx devices can have

CLKIN running before VDD is applied, and can have VDD applied and sit for extended periods with no input clock.

Note: The PWRGD_PWRDNb is synchronized with the selected CLKIN. If CLKIN is not present, the RC193xx will

not sample the pin until CLKIN is present. This applies to both powering up and powering down. If powered up

when the input clock stops, ACP (default enabled) will place the outputs into a low/low state even though the

RC193xx will not be completely powered down.

5.6

Loss of Signal and Automatic Clock Parking

The RC193xx devices have a Loss of Signal (LOS) circuit to detect the presence or absence of an input clock.

The LOS circuit drives the open-drain LOSb pin (the “b” suffix indicates “bar”, or active-low) and sets the

LOS_EVT bit in the SMBus register space. Figure 22 shows the LOSb de-assertion timing for the RC193xx clock

multiplexers. LOSb on the RC193xx multiplexers defaults to low at power up. CLKIN is represented differentially in

Figure 22 and Figure 23.

Figure 22. LOSb De-assert Timing RC193xx Devices

Note: The LOSb pin monitors the selected input clock in the RC193xx multiplexers.

Table 34. Parameters for Direct-Coupled Receiver-Terminated Configurations

ZOUT_SEL_tri

ZO (ohms)

ZDIF (ohms)

RP (ohms)

RT (ohms)

100

ZDIF /2

ZDIF

Table 35. Flexible Startup Sequences

VDD

PWRGD_PWRDNb

CLKIN/CLKINb

Not present

Running

Floating

Low/Low

Present

0 or 1

Running

Floating

Low/Low

VDD

CLKIN

LOSb

LOSDeassert typ

LOSDeassert max

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