AN3090
Application note
Power saving and LED status detection
using the STP16DPPS05 device
Introduction
Today, the use of LEDs is growing in many market segments, including portable
applications, due to their improving performance and lower cost.
This new scenario requires that LED drivers be capable of providing good performance at
low current, and include power saving capabilities.To address these requirements,
STMicroelectronics has introduced the STP16xPPx05 family of LED drivers.
This application note describes the STP16DPPS05 low voltage 16-bit constant current LED
sink driver, with particular focus on two important features: output error detection and auto
power-saving.
December 2009
Doc ID 16496 Rev 1
1/19
www.st.com
Contents
AN3090
Contents
1
2
3
4
5
Device description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Normal mode functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Error detection feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Error detection output test circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Auto power-saving feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.1
Value added by the auto power-saving feature . . . . . . . . . . . . . . . . . . . . 15
6
7
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2/19
Doc ID 16496 Rev 1
AN3090
List of tables
List of tables
Table 1.
Table 2.
Table 3.
Output error detection sequence after OE/DM2 acquisition . . . . . . . . . . . . . . . . . . . . . . . . 10
Error threshold test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Doc ID 16496 Rev 1
3/19
List of figures
AN3090
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
STP16DPPS05 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Typical data transfer from SDI to SDO . . . . . . . . . . . . . . . . . . . . . . .
Typical output_n functionality in normal mode . . . . . . . . . . . . . . . . .
Typical application of the STP16DPPS05 device . . . . . . . . . . . . . . .
Error detection sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Typical error detection results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Entering output error detection timing. . . . . . . . . . . . . . . . . . . . . . . .
Resuming normal mode timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I
DD
consumption in normal mode and auto power-saving condition.
First out “ON” after resuming normal mode . . . . . . . . . . . . . . . . . . .
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Doc ID 16496 Rev 1
AN3090
Device description
1
Device description
The STP16DPPS05 device is a monolithic, low voltage, low current power shift register.
It contains a 16-bit serial IN, parallel OUT shift register that feeds a 16-bit D-type storage
register. Sixteen regulated currents are present in the output stage, which is capable of
providing 3-40 mA of constant current to drive the LEDs.
Figure 1
shows the application
block diagram of the STP16DPPS05 device.
Figure 1.
STP16DPPS05 block diagram
Two important features of STP16DPPS05 are output status checking to detect LED errors
during driving (error detection), and power saving when the device is not managing data
(auto power safe).
Doc ID16496 Rev 1
5/19
能源基础设施
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