Delay model circuit for use in delay locked loop
View Patent ↗A delay model circuit for use in a delay locked loop (DLL) of a semiconductor device. The delay model circuit includes a first delay circuit for providing a first delay amount; a second delay circuit having N number of delay load blocks, each having a different load delay amount from others, N being a positive integer; an adjustable load control circuit for generating an adjustable load control signal; and a switching circuit for selectively coupling at least one delay load block to the first delay circuit in response to the adjustable load control signal to thereby allow the delay model circuit to provide a negative delay as a combination of the first delay amount and a second delay amount provided by the selected delay load block.
1. A delay model circuit for providing a negative delay to a delay locked loop (DLL) of a semiconductor device, comprising:
a first delay circuit for providing a first delay amount;
a second delay circuit having N number of delay load blocks, each having a different load delay amount from others, N being a positive integer;
an adjustable load control circuit for generating an adjustable load control signal, wherein the adjustable load control circuit includes
an input port for receiving an adjustable test mode signal having M number of bits, M being a positive integer; and
a decoding circuit for generating the adjustable load control signal having N number of bits by decoding the adjustable test mode signal, each bit employed in controlling each electrically controllable switch device; and
a switching circuit for selectively coupling at least one delay load block to the first delay circuit in response to the adjustable load control signal to thereby allow the delay model circuit to provide the negative delay as a combination of the first delay amount and a second delay amount provided by the selected delay load block.
2. The delay model circuit as recited in claim 1 , wherein said switching circuit includes N number of electrically controllable switching devices, each coupled between the first delay circuit and each delay load block.
3. The delay model circuit as recited in claim 2 , wherein each of the electrically controllable switching devices includes a MOS transistor.
4. The delay model circuit as recited in claim 1 , wherein the delay load block includes a capacitor-connected NMOS transistor.
5. The delay model circuit as recited in claim 1 , wherein the first delay circuit includes a plurality of inverters connected in series to each other.
6. The delay model circuit as recited in claim 1 , wherein said adjustable load control circuit further includes a fuse circuit and a power source for maintaining an adjusted test mode signal, wherein the fuse circuit includes M number of fuses for M number of bits of the adjusted test mode signal.
7. The delay model circuit as recited in claim 6 , wherein N is 8 and M is 3.