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 Title: |
US5874837:
CMOS PECL driver with programmable current for varying voltage swings and termination types
[ Derwent Title ]
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| Country: |
US United States of America
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| Inventor: |
Manohar, Amar S.; San Jose, CA
Lee, Bor; San Jose, CA
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| Assignee: |
Pericom Semiconductor Corp., San Jose, CA
other patents from PERICOM SEMICONDUCTOR CORP. (713978) (approx. 58)
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| Published / Filed: |
1999-02-23
/ 1997-04-28
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| Application Number: |
US1997000847819
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| IPC Code: |
Advanced:
H03K 19/0185;
Core:
more...
IPC-7:
H03K 19/094;
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| ECLA Code: |
H03K19/0185P;
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| U.S. Class: |
Current:
326/083;
326/082;
326/086;
Original:
326/083;
326/082;
326/086;
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| Field of Search: |
326/083,82,86,87,27,17
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| Priority Number: |
| 1997-04-28 |
US1997000847819 |
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| Abstract: |
A differential-output current driver is constructed entirely of CMOS transistors. Pseudo-ECL levels are reached when a standard resistive termination is connected to the outputs. The current driver can also drive a non-standard termination to the PECL levels. The non-standard termination is low power because it does not draw standby current from power to ground. Current from the current sources within the current driver are assigned to either the switching current or the constant current. The constant current is applied directly to the outputs to drive the termination to a bias point. The switching current is applied to a differential pair of transistors which switch the switching current to one or the other of the differential outputs in response to a differential input. The constant current is combined with any switching current output from the differential transistors and applied to the differential outputs to drive the external termination. For the non-standard termination, the differential outputs are driven with more constant current and less switching current than for the standard termination. The transconductance of the differential pair of transistors may also be increased when the switching current is increased. Thus the current-drive characteristics of a current driver are altered for different terminations. A half-sized voltage-swing option is also included.
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| Attorney, Agent or Firm: |
Auvinen, Stuart T. ;
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| Primary / Asst. Examiners: |
Tokar, Michael; Chang, Daniel D.
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| INPADOC Legal Status: |
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| Family: |
None
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First Claim:
Show all 23 claims |
We claim:
1. A complementary metal-oxide-semiconductor (CMOS) pseudo-emitter-coupled-logic (PECL) current driver for driving current to differential outputs including a first differential output and a second differential output, the CMOS PECL current driver comprising:
- a switching node for receiving currents to form a switching current;
- a first switching transistor having a gate controlled by a first differential input, the gate controlling current from the switching node to the first differential output;
- a second switching transistor having a gate controlled by a second differential input, the gate controlling current from the switching node to the second differential output;
- a first current source, connected to a power supply, for generating a first current;
- a first assignment switch, coupled to connect the first current to the switching node when an option signal is in a first state, but connecting the first current to the first differential output and not to the switching node when the option signal is not in the first state;
- a second current source, connected to a power supply, for generating a second current; and
- a second assignment switch, coupled to connect the second current to the switching node when an option signal is in a second state, but connecting the second current to the second differential output and not to the switching node when the option signal is not in the second state,
whereby the first and second currents pass through the first or second switching transistors when the option signal is in the first state, but the first and second currents bypass the first and second switching transistors when the option signal is not in the first state.
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| Background / Summary: |
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| Drawing Descriptions: |
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| Description: |
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| Forward References: |
Show 13 U.S. patent(s) that reference this one
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