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Application Note
March 2003
©2003 Silicon Storage Technology, Inc.
S72049-00-000 3/03
1
The SST logo and SuperFlash are registered trademarks of Silicon Storage Technology, Inc.
MPF is a trademark of Silicon Storage Technology, Inc.
These specifications are subject to change without notice.
INTRODUCTION
SST’s unique SuperFlash technology offers several advantages, including low power operation. Most flash memory
applications require random access times ranging from 45 ns to 200 ns. In the past, SST’s Multi-Purpose Flash
(MPF) data sheets have specified active read current ratings that are based on 70 ns test results. However, many
other flash memory vendors specify current ratings at very low speeds (typically 200 ns or slower), resulting in
lower perceived current ratings. As a result, some SST customers have been unclear about the low power advan-
tages of SST flash memories. SST is expanding its active read supply current specifications for MPF products in
order to communicate more useful information to customers. This application note explains these specification
changes, and also describes SST’s low power advantages for programming and erasing.
READ CURRENT SPECIFICATIONS (I
DD
)
Prior to 2003, SST’s MPF data sheets specified only a maximum limit (worst case) for I
DD
, the Power Supply Cur-
rent, during active read. Although it was not explicitly stated on most data sheets, this rating was based on 14 MHz
(equivalent to 70 ns) testing speed values. For existing MPF products, SST will continue to specify and test all pro-
duction devices for less than the max I
DD
specification at this speed. In addition, SST now specifies typical
1
I
DD
Active Read values in its MPF data sheets to help customers estimate typical system power usage.
In the future, SST will also specify 5 MHz (equivalent to 200 ns) maximum and typical I
DD
active read values for
MPF devices. For consistency and quality purposes, for existing products, i.e. devices that have been specified in
the past using the 14 MHz rating, SST will test production units at both the 14 MHz max spec and at the 5 MHz
max spec limits. This dual testing scheme will ensure quality and full backwards compatibility for all SST custom-
ers.
Because SST uses statistical process control methods requiring large sample sizes over time, most MPF data
sheets at the time of this publication are not updated to reflect final 5 MHz ratings. However, this chart indicates the
preliminary 5 MHz I
DD
ratings versus actual 14 MHz I
DD
ratings for SST’s MPF devices:
CURRENT AND ENERGY USAGE DURING PROGRAM AND ERASE
SST SuperFlash technology, based on SST’s patented split-gate architecture, is quite unique compared to all other
NOR flash vendors, most of whom utilize a stacked-gate architecture. These advantages and the technology
behind them are described in several of SST’s technical papers, available online at www.SST.com and in the SST
data book.
1. Typical condition ratings are average values of devices tested at 25°C (room temperature) and
V
DD
= 3V for “VF” devices (such as SST39VF040) or V
DD
= 5V for “SF” devices (such as SST39SF040).
TABLE 1: 5 MHZ (200 NS) VERSUS 14 MHZ (70 NS) I
DD
READ RATINGS
Device(s)
5 MHz Test Rating (Preliminary) 14 MHz Test Rating (Actual)
I
DD
Read
Typical (mA)
I
DD
Read
Max (mA)
I
DD
Read
Typical (mA)
I
DD
Read
Max (mA)
SST39SF512 8.5 20 10 30
SST39SF040 / 020A / 010A 8.5 20 10 25
SST39LF/VF040 / 020 / 010 / 512 4 10 5 20
SST39LF/VF800A / 400A / 200A 6 16 9 30
SST39LF/VF080 4.5 10 12 15
SST39LF/VF160/016 4.5 10 12 20
T1.1 2049
Multi-Purpose Flash Power Ratings
Multi-Purpose Flash Power Ratings
