An output that brings out only the drain of the output transistor, actively driving only the low level. The high level comes from an external pull-up resistor, so several outputs can share one line or connect to circuits on a different supply voltage. It is used on I2C buses, for example.
Japanese name: オープンドレイン
Open-drain output appears in 2 practice questions across 2 topics, including How to read datasheets, Logic circuits.
Field: How to read datasheets
Answer: B. The rise becomes faster, but the current flowing while the output is low increases, and VOL also tends to rise
The high level of an open-drain output is produced by the pull-up resistor pulling the signal line up while the output transistor is off. The rise speed is set by the time constant of the resistor and the line capacitance—for example, 1 µs for 10 kΩ and 100 pF. A smaller resistor makes it faster, but when the output is low, current flows from the supply through the resistor: 3.3 mA for 3.3 V and 1 kΩ. If this current exceeds the IOL condition in the datasheet, VOL will not stay within its specified value, so choose a value that satisfies both.
The high level of an open-drain output is produced by the pull-up resistor pulling the signal line up while the output transistor is off.
Which correctly describes the change when the value of the …An open-drain output either pulls the line to ground or releases it; a pull-up resistor provides the 1.
When several open-drain outputs are connected to one signal…As an Amazon Associate I earn from qualifying purchases.
Pull-up resistor Time constant Interrupt 5 V tolerant Absolute maximum ratings Allowable power dissipation Derating Dropout voltage Errata Exposed pad