DIGITAL TRIMMING IN A MICROELECTRONIC DEVICE

• US 20100105155A1
• Filed: 10/28/2008
• Published: 04/29/2010
• Est. Priority Date: 10/28/2008
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Peng, Jia, Jiang, Shan, Chang, Kwee Chong
• Granted Patent: US 7,760,008 B2
• Time in Patent Office: Days
• US Class Current: 438/16
• CPC Class Codes: G01R 31/318511 Wafer Test

Abstract

Digital trimming logic is included in a microelectronic device of a type that produces an output signal in response to an input signal and a threshold signal. Trimming logic values are produced in response to a clock signal that is applied to the device in a trimming mode. The clock signal can be applied to a device pin that is used in normal operation to provide an output signal, thus allowing the pin to serve a dual function. The trimming logic changes the trimming logic value in response to the clock signal until the trimming logic value reaches a trim value at which the threshold signal is substantially equal to the input signal. The trimming logic then stores the trim value in a non-volatile memory and enters a locked mode in which further trimming is prevented and the device is ready for normal operation.

Claims

1. A method for trimming a microelectronic device having an output signal responsive to an input signal and a threshold signal, the microelectronic device having trimming logic and a trimming signal generator, the trimming signal generator producing a trimming signal in response to a trimming logic value generated by the trimming logic, the method comprising:

applying a clock signal to a pin of the microelectronic device associated with the output signal in normal operation;

the trimming logic changing the trimming logic value in response to the clock signal until the trimming logic value reaches a trim value at which the trimming signal causes the threshold signal and input signal to be substantially equal to each other;

storing the trim value in a non-volatile memory;

locking the trimming logic when the trimming logic value reaches the trim value; and

outputting the trim value from the non-volatile memory to the trimming signal generator while the trimming logic is locked.

2. The method claimed in claim 1, wherein the trimming method is performed on a packaged microelectronic device.

4. The method claimed in claim 1, wherein the microelectronic device is an opto-coupler having a light source and a light detector, and the method further comprises:

while applying the clock signal, applying an input signal having a level at a minimum necessary to turn the light source on.

3. The method claimed in claim 3, further comprising:

inserting a semiconductor wafer into a probe-based test system;

applying a signal via a probe to initialize the trimming logic to an unlocked state.

5. A microelectronic device digitally trimmable in a trimming mode, comprising:

device circuitry, the device circuitry producing in a normal operational mode an output signal on a device output signal pin in response to an input signal and a threshold signal;

trimming logic, the trimming logic producing a trimming logic value in response to a clock signal received on the device output signal pin in trimming mode;

a trimming signal generator, the trimming signal generator producing a trimming signal in response to the trimming logic value, wherein the trimming logic changes the trimming logic value in response to the clock signal until the trimming logic value reaches a trim value at which trimming signal causes the threshold signal and input signal to be substantially equal to each other;

non-volatile memory, the non-volatile memory storing the trim value; and

trim output circuitry, the trim output circuitry outputting the trim value from the non-volatile memory to the trimming signal generator while the trimming logic is locked.

6. The microelectronic device claimed in claim 5, wherein the device circuitry comprises:

a light source responsive to the input signal;

a light detector optically coupled to the light source to produce a detected input signal;

threshold circuitry for producing the threshold signal, wherein the trimming signal trims the threshold signal; and

a comparator for comparing the threshold signal with the detected input signal.

7. The microelectronic device claimed in claim 5, wherein the trimming signal generator comprises a plurality of transistors, each transistor coupled to a bit of the trimming logic value.

8. The microelectronic device claimed in claim 5, wherein the trim output circuitry comprises a selector having a selection input coupled to a selection bit output by the non-volatile memory.

9. The microelectronic device claimed in claim 8, wherein:

the trim logic comprises a counter; and

the selector selectably couples one of an output of the counter and an output of the non-volatile memory to the trimming signal generator in response to the selection bit.

10. The microelectronic device claimed in claim 9, wherein:

the non-volatile memory has a serial data input and parallel data output; and

the output of the counter is connected to the serial data input of the non-volatile memory.