Jing-Reng Huang

A programmable BIST core for embedded DRAM

The programmable BIST design presented here supports various test modes using a simple controller. With the March C algorithm, the BIST circuits overhead is under 1.3% for a 1-Mbit DRAM and under 0.3% for a 16-Mbit DRAM. The BIST design presented for embedded DRAM supports built-in self-diagnosis by feeding error information to the external tester. Moreover, using a specific test sequence, it can test for critical timing faults, reducing tester time for ac parametric test. The design supports wafer test, pre-burn-in test, burn-in, and final test. It is field-programmable; the user can program test algorithms using predetermined test elements (such as march elements, surround test elements, and refresh modes). The user can optimize the hardware for a specific embedded DRAM with a set of predetermined test elements. Our design is different from the microprogram-controlled BIST described by J. Dreibelbis et al. (1998) which has greater flexibility but higher overhead. Because our design begins at the register-transfer language level, test element insertion (for higher test coverage) and deletion (for lower hardware overhead are relatively easy.

BRAINS: a BIST compiler for embedded memories

A built-in self-test (BIST) compiler for embedded memories, called BRAINS (Bist for RAm IN Seconds), is proposed. According to the memory specifications and test requirements entered by the user, BRAINS generates the synthesizable BIST code in Verilog as well as the corresponding BIST activation sequence and test-bench. The synthesis scripts for a commercial synthesis tool are also generated automatically. The architecture for the BIST circuits generated by BRAINS is an improved version of our previous design. The new design provides at-speed testing, diagnosis support, and programmable March test algorithms. The BIST compiler framework facilitates the generation of BIST circuits for various SRAM and DRAM architectures and configurations-BRAINS supports commonly used memory cores such as SRAM, EDO DRAM, SDRAM, etc. It is easy to use BRAINS for customized embedded memories. We have designed the system so that future extension to other types of memory can be done under the same framework.

Test scheduling of BISTed memory cores for SoC

The test scheduling of memory cores can significantly affect the test time and power of system chips. We propose a test scheduling algorithm for BISTed memory cores to minimize the overall testing time under the test power constraint. The proposed algorithm combines several approaches for a near-optimal result, based on the properties of BISTed memory cores. By proper partitioning, an analytic exhaustive search finds optimal results for large memory cores, while a heuristic ordering with simulated annealing further handles a large amount of smaller memory cores. On the average, the results are within 1% difference of the optimal solution for the cases of 200 memory cores.

A built-in parametric timing measurement unit

On-chip timing-measurement units are needed because accessibility to internal nodes in SoCs is very limited, and performing time interval measurements using automatic test equipment is very difficult and expensive. We present a parametric timing measurement solution, which uses self-timed techniques and delivers high linearity and improved accuracy, at low risk of measurement error. Performing the time-to-digital conversion via built-in circuitry allows accurate measurement of short time intervals and setup/hold time. This circuitry coordinates well with low-cost ATE. To achieve this solution, researchers have used techniques such as delay matrices, phase-locked loops (PLLs), and dual-slope conversion.

Automatic generation of memory built-in self-test cores for system-on-chip

Memory testing is becoming the dominant factor in testing a system-on-chip (SoC), with the rapid growth of the size and density of embedded memories. To minimize the test effort, we present an automatic generation framework of memory built-in self-test (BIST) cores for SoC designs. The BIST generation framework is a much improved one of our previous work. Test integration of heterogeneous memory architectures and clusters of memories are focused on. The automatic test grouping and scheduling optimize the overhead in test time, performance, power consumption, etc. Furthermore, with our novel BIST architecture, the BIST cores can be accessed via an on-chip bus interface (e.g., AMBA), which eases the control of testing and diagnosis in a typical SoC scenario. With a configurable and extensible architecture, the proposed framework facilitates easy memory test integration for core providers as well as system integrators.

Test scheduling and test access architecture optimization for system-on-chip

We propose an efficient test scheduling and test access architecture for system-on-chip. The test time and test control complexity are optimized under the test power and test access mechanism (TAM) resource constraints. Using our heuristic algorithms, the test scheduling can be done rapidly with small test time penalty when compared with previous works. Under an existing SoC test framework, the test access hardware can be generated from the scheduling result. Experimental results show that the proposed scheduling is hardware efficient. The system integrator can evaluate the test access architecture and perform rest scheduling systematically.

STEAC: A Platform for Automatic SOC Test Integration

The lack of electronic design automation tools for system-on-chip (SOC) test integration increases SOC development time and cost, so SOC test integration tools are important in the success of promoting SOC. We have stressed practical SOC test integration issues, including real problems found in test scheduling, test input/output (I/O) reduction, timing of functional test, scan I/O sharing, etc. In this paper, we further consider the requirement of integrating at-speed testing of embedded cores - to detect timing-related defects, our test architecture is equipped with at-speed test capability. Test scheduling is done based on our test architecture and test access mechanism, considering I/O resource constraints. Detailed scheduling further reduces the overall test time of the system chip. All these techniques are integrated into an automatic flow to facilitate SOC test integration. The test integration platform has been applied to both academic and industrial SOC cases. The chips have been designed and fabricated. The measurement results justify the approach - simple and efficient, i.e., short test integration cost, short test time, and small hardware and pin overhead.

A realistic fault model for flash memories

To explore all faulty behavior on NAND-type flash memory is impractical, and the defects in the SPICE model level are considered. In this paper, two SPICE models of the flash cell are developed and used for circuit-level faulty behavior simulation. The faulty behaviors can be classified to six types and applied for the fault modeling or testing of NAND-type flash memory.

An SOC test integration platform and its industrial realization

One of the major costs in system-on-chip (SOC) development is test cost, especially the cost related to test integration. Although there have been plenty of research works on individual topics about SOC testing, few of them took into account the practical integration issues. In this paper, we stress the practical SOC test integration issues, including real problems found in test scheduling, test IO reduction, timing of functional test, scan IO sharing, etc. A test scheduling method is proposed based on our test architecture and test access mechanism (TAM), considering IO resource constraints. Detailed scheduling further reduces the overall test time of the system chip. We also present a test wrapper architecture that supports the coexistence of scan test and functional test. The test integration platform has been applied to an industrial SOC case. The chip has been designed and fabricated. The measurement results justify the approach-simple and efficient, i.e., short test integration cost, short test time, and small area overhead.

A chaos-based fully digital 120 MHz pseudo random number generator

A chaos-based pseudo random number generator (PRNG) is implemented in a fully digital circuit with 120 MHz operation clock frequency. The chaotic equation called logistic equation is applied to the system model of PRNG. Noise can be injected to disturb the iterations with dead operation detected. The random quality of the chaos-based model is measured by the Sp. 800-22 random test package. The chaos-based PRNG has been designed and run in the UMC 1P6M 0.18/spl mu/m CMOS process with area of 944 /spl mu/m /spl times/ 813 /spl mu/m.