CM2031 데이터 시트보기 (PDF) - ON Semiconductor

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CM2031

HDMI Receiver Port Protection and Interface Device

ON Semiconductor 

CM2031

4mA for the ASIC on DDC_XX_IN, the CM2031 guarantees no more than 140mV increase to DDC_XX_OUT,

even with a switching control of 2.5V on LV_SUPPLY.

Additionally, when I2C devices are driving the external cable, an internal pulldown on DDC_XX_IN guarantees

that the VOL seen by the ASIC on DDC_XX_IN is equal to or lower than DDC_XX_OUT.

Multiport DDC Multiplexing

Additionally, by switching LV_SUPPLY, the DDC/HPD blocks can be independently disabled

by engaging their inherent “backdrive” protection. This allows N:1 multiplexing of the low-

speed

HDMI

signals

without

any

additional

FET

switches.

Consumer Electronics Control (CEC)

The Consumer Electronics Control (CEC) line is a high level command and control protocol, based on a single

wire multidrop open drain communication bus running at approximately 1kHz (See Figure 3). While the HDMI link

provides only a single point-to-point connection, up to ten (10) CEC devices may reside on the bus, and they may

be daisy chained out through other physical connectors including other HDMI ports or other dedicated CEC links.

The high level protocol of CEC can be implemented in a simple microcontroller or other interface with any I/OD

(input/open-drain) GPIO.

CEC

RX

I/OD

GPIO

TX

Figure 3. Typical µC I/OD Driver

To limit possible EMI and ringing in this potentially complex connection topology, the rise- and fall-time of this line

are limited by the specification. However, meeting the slew-rate limiting requirements with additional discrete

circuitry in this bi-directional block is not trivial without an additional RX/TX control line to limit the output slew-rate

without affecting the input sensing (See Figure 4).

CEC

RX

TX

TX_EN

Slew Rate

Limited

3-State Buffer

X

Figure 4. Three-Pin External Buffer Control

Simple CMOS buffers cannot be used in this application since the load can vary so much (total pullup of 27kΩ to

less than 2kΩ, and up to 7.3nF total capacitance.) The CM2031 targets an output drive slew-rate of less than

100mV/µs regardless of static load for the CEC line. Additionally, the same internal circuitry will perform active

Rev. 5 | Page 6 of 18 | www.onsemi.com

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