psd511b1 STMicroelectronics, psd511b1 Datasheet - Page 9

• Manufacturer Part Number: psd511b1
• Description: Low Cost Field Programmable Microcontroller Peripherals
• Manufacturer: STMicroelectronics

5.0
Integrated
Power
Management
Operation
6
PSD5XX Family
TM
Figure 2. ZPSD Power Operation vs. Discrete Implementation
Upon each address or logic input change to the PSD, the device powers up from low power
standby for a short time. Then the PSD consumes only the necessary power to deliver new
logic or memory data to its outputs as a response to the input change. After the new
outputs are stable, the PSD latches them and automatically reverts back to standby mode.
The I
The PSD automatically reduces its DC current drain to these low levels and does not
require controlling by the CSI (Chip Select) input. Disabling the CSI pin unconditionally
forces the PSD to standby mode independent of other input transitions.
The only significant power consumption in the PSD occurs during AC operation.
The PSD contains the first architecture to apply Zero-power techniques to memory circuit
blocks as well as logic.
Figure 2 compares PSD Zero-power operation to the operation of a discrete solution.
A standard microcontroller (MCU) bus cycle usually starts with an ALE (or AS) pulse and
the generation of an address. The PSD detects the address transition and powers up for a
short time. The PSD then latches the outputs of the PAD, EPROM and SRAM to the new
values. After finishing these operations, the PSD shuts off its internal power, entering
standby mode. The time taken for the entire cycle is less than the PSD’s “access time.”
The PSD will stay in standby mode if the inputs do not change between bus cycles. In an
alternate system implementation using discrete EPROM, SRAM and other discrete
components, the system will consume operating power during the entire bus cycle. This is
because the chip select inputs on the memory devices are usually active throughout the
entire cycle. The AC power consumption of the PSD may be calculated using the composite
frequency of the MCU address and control inputs, as well as any other logic inputs to the
ZPLD.
NOTE: The ZPSD5XX parts have been rated for a lower standby current (I
PSD5XX parts.
I
ADDRESS
CC
ALE
CC
DISCRETE EPROM, SRAM & LOGIC
current flowing during standby mode and during DC operation is identical.
ZPSD
ACCESS
EPROM
TIME
ZPSD
ACCESS
SRAM
ZPSD
SB
ACCESS
) than the
EPROM