Semiconductor memory module and semiconductor memory system having termination resistor units
A semiconductor memory module includes a memory module board having at least one semiconductor memory device. The semiconductor memory device includes a data input buffer that receives data and a first reference voltage via first and second input terminals, a command/address buffer that receives a command/address signal and a second reference voltage via first and second input terminals, and a first termination resistor unit connected to the first input terminal of the data input buffer. The semiconductor memory module further includes a second termination resistor unit located on the memory module board and connected to an internal command/address bus. The first termination resistor unit includes a first resistor connected between a first voltage source and the first input terminal of the data input buffer, and the second termination resistor unit includes a second resistor connected between a second voltage source and the first input terminal of the command/address input buffer.
1. A semiconductor memory module comprising:
a memory module board comprising at least one semiconductor memory device, wherein the at least one semiconductor memory device comprises:
a data input buffer receiving data via a first input terminal and receiving a first reference voltage via a second input terminal;
a command/address input buffer receiving a command/address signal via a first input terminal and receiving a second reference voltage via a second input terminal; and
a first termination resistor unit connected to the first input terminal of the data input buffer;
an internal command/address bus providing the command/address signal to the command/address input buffer; and
a second termination resistor unit located on the memory module board and connected to the internal command/address bus,
wherein the first input terminal of the data input buffer has a first signal swing level based on a first termination type of the first termination resistor unit, and the first input terminal of the command/address input buffer has a second signal swing level based on a second termination type of the second termination resistor unit,
wherein the first reference voltage has a first level corresponding to the first signal swing level, and the second reference voltage has a second level corresponding to the second signal swing level, and
wherein at least one of the first reference voltage and the second reference voltage are obtained by performing calibration based on at least one of the first termination type and the second termination type.
2. The semiconductor memory module of claim 1 , wherein each of the at least one semiconductor memory device further comprises:
a voltage adjustment unit receiving a predetermined voltage and generating the first reference voltage and the second reference voltage from the predetermined voltage.
3. The semiconductor memory module of claim 2 , wherein a first voltage adjustment unit included in a first semiconductor memory device and a second voltage adjustment unit included in a second semiconductor memory device perform calibration independently of each other, such that at least one of the first and second levels of the first and second reference voltages generated in the first voltage adjustment unit is different from at least one of the first and second levels of the first and second reference voltages generated in the second voltage adjustment unit.
4. The semiconductor memory module of claim 1 , wherein the first termination resistor unit comprises a first resistor connected between a first power supply voltage source and the first input terminal of the data input buffer, and
wherein the second termination resistor unit comprises a second resistor connected between a second power supply voltage source and the first input terminal of the command/address input buffer; and a third resistor connected between a ground voltage source and the first input terminal of the command/address input buffer.
5. The semiconductor memory module of claim 4 , wherein the calibration is performed on the first reference voltage, and
the first reference voltage has a level between the first power supply voltage and the second reference voltage.
6. The semiconductor memory module of claim 1 , wherein the first termination resistor unit comprises a first resistor connected between a first power supply voltage source and the first input terminal of the data input buffer, and a second resistor connected between a ground voltage source and the first input terminal of the data input buffer; and
wherein the second termination resistor unit comprises a third resistor connected between a second power supply voltage source and the first input terminal of the command/address input buffer.
7. The semiconductor memory module of claim 6 , wherein the calibration is performed on the second reference voltage, and
the second reference voltage has a level between the second power supply voltage and the first reference voltage.