Serial-interfaced 6-digit LED controller with keyscan
Features
■ LED driver with 14 outputs
(8 segments/6 digits)
■ 40 mA load current capability for each segment
■ Output pins connected directly to the LEDs or
can be open-drain
■ Key-scanning (8 x 2 matrix)
■ Low power consumption in standby mode
■ 3-wire serial bus interface (CLK, STB,
DIN/DOUT)
■ 8-step dimming circuit to control the overall
display brightness
■ Single external resistor for output current
setting
■ Inputs with Schmitt trigger give superior noise
immunity
■ A single LED digit output (DIG1_LED) can be
used to drive up to 8 discrete LEDs
■ 8-step dimming circuit to control brightness of
individual LEDs for LED digit
■ 5.0 V (± 10%) for V
■
Drives common-anode LED digits
■ Built-in power on reset and soft-start circuits
■ Available in SO24 package
■ -40 °C to 85 °C operating temperature range
Applications
■ Set-top-boxes
■ White goods
■ Home appliances
■ DVD players and VCRs
Table 1. Device summary
CC
STLED316S
SO-24
Description
The STLED316S is a compact LED controller and
driver that interface microprocessors to LED
displays through a serial 3-wire interface. It drives
LED connected in common anode configuration.
The STLED316S drives up to 48 discrete LEDs in
8 segment/6 digit configuration while functioning
from a supply voltage of 5.0V. Additionally it can
be used to drive 8 discrete LEDs which form a
part of LED digit. The individual LEDs are wired
as segments of a digit and brightness of these
individual LEDs can be controlled digitally. The
maximum segment current for the display digits is
set through a single external resistor. Individual
digits may be addressed and updated without rewriting the entire display.
Additionally it includes key scanning for an 8x2
key matrix which automatically scans a matrix of
up to 16 switches. STLED316S supports numerictype displays and reduces the overall BOM costs
through high integration. Also it provides ESD
protection of greater than 4 kV HBM.
The LED controller/driver is ideal as a peripheral
device to interface the display with a singlechip
microcomputer.
Part number Package Packaging
STLED316SMTR SO-24 Tape and reel
January 2008 Rev 1 1/33
www.st.com
33
Contents STLED316S
Contents
1 STLED316S functional and application diagram . . . . . . . . . . . . . . . . . . 3
2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3 STLED316S functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1 Low power mode of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2 Serial interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3 Initial power up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.4 Display types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.5 Keyscan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.6 Discrete LED outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.7 Power on reset and soft-start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.8 LED drivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.9 Interrupt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.10 Operating the device with 3.3 V interface voltages . . . . . . . . . . . . . . . . . . 9
4 Maximum rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.1 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5 Recommended operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.1 DC electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.2 Power consumption estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.3 Capacitance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.4 Power supply characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.5 Dynamic switching characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.6 Timing characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.7 ESD performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6 Key-scan & display cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7 Key matrix and key-input data storage ram . . . . . . . . . . . . . . . . . . . . . 15
8 Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2/33
STLED316S Contents
8.1 Write command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
8.2 Read command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.3 Device configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8.3.1 Display setting (maximum number of digits): . . . . . . . . . . . . . . . . . . . . . 19
8.3.2 Dimming setting (brightness levels): . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.4 Display memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
9 Key-scanning and display timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
9.1 Serial communication format (reception) . . . . . . . . . . . . . . . . . . . . . . . . . 23
9.2 Serial communication format (transmission) . . . . . . . . . . . . . . . . . . . . . . 24
10 Switching characteristics waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
11 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
11.1 Graph of ISET against RSET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
11.2 Power supply sequencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
11.3 Application diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
12 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
13 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3/33
List of figures STLED316S
List of figures
Figure 1. STLED316S functional diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Figure 2. STLED316S application diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Figure 3. STLED316S pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure 4. Key matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Figure 5. Serial communication format (reception) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Figure 6. Serial communication format (transmission). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Figure 7. Switching characteristics waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Figure 8. Graph of ISET against RSET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Figure 9. STLED316S application diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Figure 10. SO-24 package outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4/33
STLED316S List of tables
List of tables
Table 1. Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Table 2. Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Table 3. Seven segment display with dot point and common-anode LED panel . . . . . . . . . . . . . . . 11
Table 4. Absolute maximum ratings (all voltages are referenced to GND). . . . . . . . . . . . . . . . . . . . 13
Table 5. Thermal data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Table 6. DC electrical characteristics
(T
= -40 to +85 °C, VCC= 5.0 V ± 10%, GND = 0 V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Table 7. Capacitance (T
Table 8. Power supply characteristics (TA = -40 to +85 °C) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Table 9. Dynamic switching characteristics
Table 10. Timing characteristics
Table 11. ESD performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 12. Read command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Table 13. Memory page mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Table 14. Digit address mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Table 15. LED address mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Table 16. Memory page address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Table 17. 7-segment display address. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Table 18. LED display address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Table 19. Part list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Table 20. SO-24 package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Table 21. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
A
(TA = -40 to +85 °C, VCC = 5.0 V ± 10%, GND = 0.0 V, typical values are at 25 °C) . . . . 16
(TA = -40 to +85 °C, V
= 25 °C, f = 1 MHz) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
A
= 5.0 V ± 10%, GND = 0.0 V, Typical values are at 25 °C) . . . . 16
CC
5/33
STLED316S functional and application diagram STLED316S
1 STLED316S functional and application diagram
The STLED 316S consists of the following blocks:
● Current source
● POR and soft-start
● Interrupt generator
● Serial interface
● Digital logic blocks
● Drivers
Figure 1. STLED316S functional diagram
ISET
DIN/DOUT
CLK
STB
KEY1-KEY2
Current
source
Internal clock
generator
2
Serial
I/F
Output
segments
VCC
Command
decoder
Display memory
(7 x 8)
Timing gen.
keysan & dimming
Keydata memor y
(2 x 8)
POR
&
soft-start
8-bit
output
latch
7-bit
shift
register
V
CC
(+5.0 V)
Internal
reset
GND
(0 V)
8
7
Interrupt
generation
IRQ_N
SEG1/KS1
SEG8/KS8
DIG1_LED
DIG7
DIG2
6/33
STLED316S STLED316S functional and application diagram
Figure 2. STLED316S application diagram
6
MCU
DIN / DOUT
IRQ_N
RSET
CLK
STB
ISET
STLED316S
KEY1-KEY2
Keyscan
(8 x 2 matrix)
8
SEG1/KS1
-SEG8/KS8
DIG2-DIG7
DIG1_LED
LED 6-digit 7-segment (+dot-point) display panel
CS00014
7/33
Pin description STLED316S
2 Pin description
Figure 3. STLED316S pin connection
Table 2. Pin description
Pin number Symbol Type Name and function
Output serial data at falling edge of the shift clock,
1 DIN/DOUT IN/OUT
2CLK IN
3STB IN
4IRQ_NOUT
5 DIG1_LED OUT
6,7,8
9V
DIG2, DIG3,
DIG4
CC
OUT Digit output pins.
PWR
starting from lower bit. Input serial data is clocked in at
rising edge of the shift clock, starting from lower bit.
Reads serial data at rising edge, and outputs data at
falling edge.
Initializes serial interface at rising or falling edge to
make STLED316S wait for reception of command.
Data input after the falling edge of STB are processed
as a command. While command data are processed,
current processing is stopped, and the serial interface
is initialized. While STB is high, instructions are
ignored.
Interrupt output (active low) to interrupt the MCU
when there is a key press
Single output LED used together with the 8 segments
to drive up to 8 discrete LEDs
5.0 V ± 10% Core main supply voltage. Bypass to
GND through a 0.1 µF capacitor as close to the pin as
possible.
10,11,12
8/33
DIG5, DIG6,
DIG7
OUT Digit output pins.
STLED316S Pin description
Table 2. Pin description (continued)
Pin number Symbol Type Name and function
SEG8/KS8
13,14,15,16
17 GND PWR Connect this pin to system GND.
18,19,20,21
22 KEY2 IN
23 KEY1 IN
to
SEG5/KS5
SEG4/KS4
to
SEG1/KS1
OUT Segment output pins (dual function as key source).
OUT Segment output pins (dual function as key source).
Key 2 input. Input data to these pins from external
keyboard are latched at end of the display cycle
(maximum keyboard size is 8 x 2).
Key 1 input. Input data to these pins from external
keyboard are latched at end of the display cycle
(maximum keyboard size is 8 x 2).
24 ISET IN
Segment current setting. Connect to GND through a
resistor to set the peak segment current.
9/33
STLED316S functional description STLED316S
3 STLED316S functional description
The STLED316S is a common-anode LED driver controller which can be used to drive red,
green or blue LEDs as the current is adjustable through the external resistor. In the common
anode configuration, the segment outputs sink the current from the cathodes while the digit
outputs source the current to the anodes. The configurable output current can be used to
drive LEDs with different current ratings (red, green or blue). The brightness of the whole
display can be controlled through the serial interface as described later. The outputs can be
connected together in parallel to drive a single LED. In this case, two parallel current
sources of equal value drive a single LED. The external resistor value can be set accordingly
to determine the desired output current thus controlling the display brightness.
Soft-start limits the inrush current during power-up. The display is blanked (LEDs are turned
off or in high-Z state) on power-up.
3.1 Low power mode of operation
Upon initial power up or when not configured or when not used, the STLED316S will be in
low power mode of operation wherein the current consumption drops to less than 1mA.
During this mode, the data configured is maintained as long as the supply voltage is still
present (the contents of the internal RAM need the supply voltage to be present). Port
configuration and output levels are restored when the STLED316S resumes normal
operation. For minimum supply current in shutdown mode, logic inputs should be at GND or
V
.
CC
3.2 Serial interface
The interface is used to write configuration and display data to the STLED316S. The serial
interface comprises of a shift register into which DIN is clocked on the rising edge of the
CLK when STB is low. When STB is low, falling transitions on CLK clock the data from the
device to the microcontroller. The 8-bit data is decoded to determine and execute the
command.
STB indicates to the device the start of communication when it goes low. DIN/DOUT pin is
bi-directional. The data will be validated during positive pulse of the clock in both write/read
modes. If the STB signal goes high before completing the data byte write to the device, the
preceding data bits are ignored and the previous configuration remains intact.
3.3 Initial power up
On initial power-up, all control registers are reset, the display is blanked and the
STLED316S is in the low power mode. All the outputs are in high-impedance state at initial
power-up. The DIN/DOUT is pulled high by an external pull-up resistor. The display driver
has to be configured before the display can be used.
10/33
STLED316S STLED316S functional description
3.4 Display types
Table 3. Seven segment display with dot point and common-anode LED panel
3.5 Keyscan
The full keyscan is illustrated in the another section of the datasheet. One diode is required
per key switch. The keyscan circuit detects any combination of keys being pressed.
3.6 Discrete LED outputs
The STLED316S can be used to drive up to 8 discrete LEDs. The single LED output acts
like a digit driver output and can be wired-up with 8 segment outputs to drive up to 8 different
discrete LEDs. Physical connections from the LED output as well as the segment outputs
must be made to drive the discrete LEDs in the desired manner. The discrete LEDs may be
needed to indicate the “Power”, “Standby” status (for example). Also it is possible to
separately control the brightness of each single LED.
3.7 Power on reset and soft-start
The device integrates an internal power-on-reset circuit which initializes the digital logic
upon power up. The soft-start circuit limits the inrush current and high peak current during
power-up. This is done by delaying the input circuit’s response to the external applied
voltage. During soft-start, the input resistance is higher which lowers the in-rush current
when the supply voltage is applied.
11/33
STLED316S functional description STLED316S
3.8 LED drivers
The constant current capability is up to 40 mA per output segment and is set for all the
outputs using a single external resistor. When acting as digit drivers, the outputs source
current to the display anodes. When acting as segment drivers, the LED outputs sink current
from the display cathodes. The outputs are high impedance when not being used as digit or
segment drivers.
Each port configured as a LED digit driver behaves as a digitally-controlled constant current
sink. The LED drivers are suitable for both discrete LEDs and common anode (CA) numeric
LED digits. When fully configured as a LED driver, the STLED316S controls up to 8 LED
segments in a single digit with 8-step logarithmic brightness control for the digits. A single
resistor sets the maximum segment current for all the segments, with a maximum of 40mA
per segment. The STLED316S drives any combination of discrete LEDs and CA digits for
numeric displays.
The recommended value of R
driver to the maximum allowed segment current. R
segment current to a lower maximum value where desired. The user must also ensure that
the maximum current specifications of the LEDs connected to the drivers are not exceeded.
The brightness of the individual digits in the display panel can be controlled separately.
is the minimum allowed value, since it sets the display
SET
can be a higher value to set the
SET
3.9 Interrupt
The device includes an active low level IRQ_N pin to the microprocessor. The STLED316S
generates an interrupt when a key is pressed.
3.10 Operating the device with 3.3 V interface voltages
The device can detect the input voltage levels reference to 3.3 V from the main controller
chip as long as the V
voltage to STLED316S is greater than 2.9 V, the STLED316S will recognize the signal level
as a valid high and if the input voltage is lower than 1.75 V, it will be recognized as a valid
low level.
For the output signals from the device like DOUT and IRQ_N, the signal level depends on
the external supply to which the external pull up resistor is connected to. Thus this
eliminates the use of any level shifter between the main controller and the STLED316S.
and VIH specifications of the STLED316S are met. If the input
IL
12/33
STLED316S Maximum rating
4 Maximum rating
Stressing the device above the rating listed in the “Absolute maximum ratings” table may
cause permanent damage to the device. These are stress ratings only and operation of the
device at these or any other conditions above those indicated in the operating sections of
this specification is not implied. Exposure to absolute maximum rating conditions for
extended periods may affect device reliability. Refer also to the STMicroelectronics SURE
program and other relevant quality documents.
Table 4. Absolute maximum ratings (all voltages are referenced to GND)
Symbol Parameters Values Unit
V
CC
V
I
P
D
T
A
T
J
T
STG
T
L
V
ESD
1. De-rate at -9.6 mW/°C at TA = 25°C or higher
2. In accordance with the JEDEC standard
Supply voltage to ground -0.5 to +7.0 V
Logic input voltage -0.5 to VCC+0.5 V
Power dissipation
Operating ambient temperature -40 to 85 °C
Junction temperature 150 °C
Storage temperature -65 to +150 °C
Lead temperature (10 sec) 300 °C
Electrostatic discharge voltage on all pins
Human body model
4.1 Thermal data
Table 5. Thermal data
Symbol Parameter Min Typ Max Unit
T
thJC
Thermal resistance junction-ambient 75 °C/W
(1)
1200 mW
(2)
-4 to +4 kV
13/33
Recommended operating conditions STLED316S
5 Recommended operating conditions
5.1 DC electrical characteristics
Table 6. DC electrical characteristics
(T
= -40 to +85 °C, VCC= 5.0 V ± 10%, GND = 0 V)
A
Symbol Parameter Test conditions Min Typ Max Unit
V
CC
V
V
, I
I
IH
V
HYS
V
OL(DOUT)
I
OLEAK
I
SEG
I
DIG
I
TOLSEG
R
SET
Logic supply voltage 4.5 5.0 5.5 V
High level input voltage
IH
Low level input voltage
IL
Input current VIN = VCC or GND -2 2 µA
IL
High level guaranteed
digital pins
Low level guaranteed
digital pins
Hysteresis voltage
(DIN, CLK, STB pins)
Low level output voltage DOUT, I
=4mA 0.4 V
OL2
0.57
V
CC
0
0.91.051.2 V
Driver leakage current Drivers off -140 µA
V
=2.5V
Segment drive LED sink current
Digit drive LED source current V
Segment drive current matching
LED
V
DIGIT=VCC
DIGIT
V
= 5.0 V, TA=25°C
CC
V
=2.5V
LED
–1.0
= VCC – 1.0 240 320 400 mA
-30 -40 -50 mA
3%
External current setting reference
resistor
= 40 mA 360 Ω
I
SEG
(precision = ±1% tolerance)
V
CC
0.3V
CC
V
V
14/33
STLED316S Recommended operating conditions
5.2 Power consumption estimation
Each port of the STLED316S can sink a maximum current of 40 mA into an LED with a
4.4 V forward voltage drop when operated from a supply voltage of 5.0 V. The minimum
voltage drop across the internal LED drivers is thus 5.0 - 4.4 = 0.6 V. The STLED316S can
sink 8 x 40 = 320 mA when all outputs are operating as LED segment drivers at full current.
On a 5.0 V supply, a STLED316S dissipates (5.0 V - 4.4 V) x 320 mA = 192 mW when
driving 8 of these 4.4 V forward voltage drop LEDs at full current. If the application requires
high drive current, consider adding a series resistor to each LED to drop excessive drive
voltage off-chip.
If the forward voltage of the LED is lesser than 4.4 V (say 2.4 V), then the maximum power
dissipation of STLED316S when all segments are turned on will be ( 5 - 2.4) V x
320 mA = 832 mW. To lower the power dissipation, consider adding a small series resistor
in the supply. Another alternative is to increase the value of the R
the LEDs from 40 mA to say 30 or 20 mA.
The efficiency will be the power consumption in the LEDs divided by the input power
consumed.
to lower the current of
SET
Efficiency = V
diode
x I
diode
/ VCC x I
CC
As an example, consider LED with forward voltage of VF = 2.4V, I
V
CC (max)
Power dissipation, P
= 5.5 V, N = number of segments = 8 (max), D = duty cycle = 15/16,
D (max)
= 5 mA x 5.5 V + (5.5 - 2.4) V x (15/16) x 40 mA x 8 = 27.5 + 780
= 807.5 mW. To lower this value, add a series resistor with the supply.
5.3 Capacitance
Table 7. Capacitance (TA=25°C, f=1MHz)
Symbol Parameter Test conditions Min Typ Max Unit
C
Input capacitance 15 pF
IN
5.4 Power supply characteristics
Table 8. Power supply characteristics (TA = -40 to +85 °C)
Symbol Parameter Test conditions Min. Typ. Max. Unit
= 5.5 V,
I
STBY
I
CC
Quiescent power supply
current
Operating power supply
current
(display ON)
V
CC
All inputs = V
All segments ON, all digits
scanned, intensity set to full,
internal oscillator, no display
load connected
CC
or GND
= 40 mA,
peak
50 1000 µA
10 15 mA
15/33
Recommended operating conditions STLED316S
5.5 Dynamic switching characteristics
Table 9. Dynamic switching characteristics
(T
= -40 to +85 °C, VCC= 5.0 V ± 10%, GND = 0.0 V, typical values are at
A
25 °C)
Symbol Parameter Test conditions Min. Typ. Max. Unit
f
f
t
t
Internal oscillation frequency 400 500 600 kHz
OSC
Clock (CLK) frequency Duty = 50% 1 MHz
MAX
Propagation delay
PLZ
PZL
5.6 Timing characteristics
Table 10. Timing characteristics
(T
= -40 to +85 °C, VCC= 5.0 V ± 10%, GND = 0.0 V, Typical values are at
A
25 °C)
Symbol Parameter Test conditions Min. Typ. Max. Unit
PW
PW
t
SETUP
t
HOLD
t
CLK-STB
Clock pulse width 400 ns
CLK
Strobe pulse width 1 µs
STB
Data setup time 100 ns
Data hold time 100 ns
Clock-strobe time
CLK to DOUT
RL=10KΩ, CL=15pF
CLK rising edge to STB
rising edge
300 ns
100 ns
1µs
5.7 ESD performance
Table 11. ESD performance
Symbol Parameter Test conditions Min. Typ. Max. Unit
ESD JEDEC standard (all pins) HBM ±4kV
16/33
STLED316S Key-scan & display cycle
6 Key-scan & display cycle
The display RAM stores the data transmitted from an external device to the STLED316S
through the serial interface. Refer to Section 9: Key-scanning and display timing on page 25
for a pictorial representation.
The grid and segment outputs are controlled by the display output module. The entire grid
will be turned off on channel 1/16 and 16/16 meaning that the first channel and last channel
are off. This is referred to as blanking time.
During the keyscan time (first cycle from timing generator), the entire grid is turned off and
only the segments are enabled one by one (seg0 to seg7). The segment on time is 64 µs.
During the LED discrete time (second cycle), the data present on the internal LED buffer is
checked. If the data is present, then the brightness setting of each LED in the brightness
control register is checked. Then each segment will be enabled or disabled based on the
register value. In this duration, the grids 1 to 6 are turned off. The grid corresponding to LED
digit is turned on. The LED on duty cycle is 14/16. If the LED/seg1 brightness is 12/16, it
means that the segment1 OFF time is 12/16 and on time is 2/16.
During 7-segment display time (3
it is ON or OFF. If display is ON, then the dimming settings are checked from the
configuration register for the grid (it may be common dimming setting or individual dimming
setting for each digit). The minimum turn on time is 1/16 and maximum turn on time is 14/16.
The blanking time is valid before the turning on and turning off of the grid. The blanking
interval is 32 µs. This will continue until the maximum number of digits configured in the
register. Once the full cycle is complete, the keyscan cycle will start again.
rd
cycle to 8th cycle), the display status is checked whether
If the display is not turned on, then the timing generation will immediately go to the key scan
mode.
Initial:
All the segments and grids are turned off.
During operation:
1. Turn on segment (keyscan) one by one. On time duration is 64 µs.
2. Check the data present in LED register. If data is present, turn on the respective LED
grid and segments.
3. Check the display on. If display is turned on, then enable the grid one by one from grid
1 to grid 6 (maximum) and turn on segments.
17/33
Key matrix and key-input data storage ram STLED316S
7 Key matrix and key-input data storage ram
During the key scan cycle all the grids are turned off. The first segments turn on is 64 µs.
The key1 and key2 signals will be sampled after 60 µs. The two signals latch into the
internal key buffer. The same applies for other segments.
This key buffer compares the data with the previous key status. If any changes are seen in
the buffer values, then the IRQ_N is asserted. The IRQ_N signal is active low (level). This
IRQ_N signal will be cleared at the end of reading the key buffer (end of byte transfer). The
key buffer must be completely read before the IRQ_N is cleared.
The key matrix is of 8 x 2 configuration, as shown below:
Figure 4. Key matrix
The data of each key are stored as illustrated below, and are read by the appropriate read
command, starting from the least significant bit.
1st byte
KEY1 KEY1 KEY1 KEY1 KEY1 KEY1 KEY1 KEY1
SEG1/KS1 SEG2/KS2 SEG3/KS3 SEG4/KS4 SEG5/KS5 SEG6/KS6 SEG7/KS7 SEG8/KS8
LSB MSB
nd
byte
2
KEY2 KEY2 KEY2 KEY2 KEY2 KEY2 KEY2 KEY2
SEG1/KS1 SEG2/KS2 SEG3/KS3 SEG4/KS4 SEG5/KS5 SEG6/KS6 SEG7/KS7 SEG8/KS8
LSB MSB
The initial key buffer value is “00”. During operation, the buffer values will change depending
upon the values of the key-press.
18/33
STLED316S Commands
8 Commands
Command sets the display mode and the status of the LED driver. The first byte input to the
STLED316S through the DIN input after the STB goes low is regarded as a command. If
STB is set high while commands/data are transmitted, serial communication is initialized,
and the commands/data being transmitted are invalid (however, the commands/data already
transmitted remain valid).
8.1 Write command
MSB 8 MSB 7 MSB6 MSB5 LSB4 LSB3 LSB2 LSB1
Description: LSB 3 -1 → address of the memory
MSB5 and LSB4
MSB
→ 6 ‘0’ auto increment address
→ address of memory bank (page)
‘1’ fixed address
MSB 7
→ ‘0’ Write command
‘1’ Read command
MSB 8
→ ‘X’ Unused
The following bytes are either configuration data or display data.
During the write command, the control flag display on and auto increment address are
latched into the internal control flag register. The default value is ‘0’ for display on control
register implying that the display is off. The user must turn on the display to view the display
memory. Similarly the auto increment address mode is enabled by default. If the user
desires to read from a particular address location, the user can fix the address pointer.
Display on:
MSB 8 MSB 7 MSB6 MSB5 LSB4 LSB3 LSB2 LSB1
x 0 X01101
Display off:
MSB 8 MSB 7 MSB6 MSB5 LSB4 LSB3 LSB2 LSB1
x 0 X01110
Use these two commands to turn the display ‘ON’ and ‘OFF’.
19/33
Commands STLED316S
8.2 Read command
MSB 8 MSB 7 MSB6 MSB5 LSB4 LSB3 LSB2 LSB1
Description: LSB 3 -1 → address of the memory
MSB5 and LSB4
MSB 6
→ ‘0’ auto increment address
→ address of the memory bank (page)
‘1’ fixed address
MSB 7
→ ‘0’ Write command
‘1’ Read command
MSB 8
→ ‘X’ Unused
Use the page 0x01 to read the LED data and key data.
Table 12. Read command
Address Function
00 LED data (optional)
01 Key data byte1
02 Key data byte2
Set flag for key1 and key2 to ensure that the user reads from the particular key. When
reading the key data from the memory, the IRQ_N will be automatically cleared signifying
that the end of the 8
th
bit was transmitted correctly.
If the IRQ_N is asserted by the last eight keys, then the user reads the key data (one byte
only by reading the first byte). In this case, the IRQ_N will remain active until the second
byte is read. When the user uses the read key to read the LED and key data, first the user
must choose the address (default address location is 0x00) after which the address will
increment only by 3 addresses (maximum).
8.3 Device configuration
This section describes how to program and read the configuration of the device.
Configuration data comprises of the display setting, dimming setting, display on/off and fixed
20/33
STLED316S Commands
address/auto increment. The address pointer will indicate the configuration location and
write signal writes the configuration data into the respective location.
The memory block is split into two page locations. One is for the 7-segment brightness
configuration memory and the other is for the LED (discrete) configuration memory. The
configuration memory address starts from 0x00 to 0x07. The configuration page address is
“10” and “11”.
Initial Value:
Table 13. Memory page mapping
Memory page Address Value
10 00 0xFB
10 01 0x00
10 02 0x00
10 03 0x00
11 00 0x00
11 01 0x00
11 02 0x00
11 03 0x00
Description: Address 0x00; page 0x10
LSB 0 – 2
LSB3 MSB 4
→ indicates the number of digits in the display
→ '11' is for constant brightness control for the display
→ '00' is for variable brightness control for the display
→ '01' is reserved
→ '10' is reserved
MSB 5 – 7
Default is constant brightness control with 14/16 pulse width (for maximum brightness).
Page 0x10 - address 0x01 to 0x03 is for the variable brightness control value for 7
segments:
Table 14. Digit address mapping
→ indicates constant brightness control value for all including the LED
(discrete)
Address MSB LSB
0x01 Digit 2 Digit 1
0x02 Digit 4 Digit 3
0x03 Digit 6 Digit 5
Default is constant brightness control with 14/16 pulse width.
Page0x11 - address 0x00 to 0x03 is for the variable brightness control value for LED
(discrete)
21/33
Commands STLED316S
Table 15. LED address mapping
Address MSB LSB
0x00 LED/ Seg 2 LED/ Seg 1
0x01 LED/ Seg 4 LED/ Seg 3
0x02 LED/ Seg 6 LED/ Seg 5
0x03 LED/ Seg 8 LED/ Seg 7
Default is constant brightness control with 14/16 pulse width.
During normal operation, the user defined value will be stored in the respective location.
8.3.1 Display setting (maximum number of digits):
The 3-bit values corresponding to selection of number of digits of display are shown below:
000: 1 digit 8 segments
001: 2 digits 8 segments
010: 3 digits 8 segments
011: 4 digits 8 segments
100: 5 digits 8 segments
101: 6 digits 8 segments
Select the number of digits by writing the value in page 0x10 and the address 0x00 in LSB2
to LSB0.
8.3.2 Dimming setting (brightness levels):
The 4-bit values corresponding to different brightness levels are shown below:
0000: pulse width is 1/16
0001: pulse width is 2/16
0010: pulse width is 4/16
0011: pulse width is 10/16
0100: pulse width is 11/16
0101: pulse width is 12/16
0110: pulse width is 13/16
0111: pulse width is 14/16
Set the dimming timing (write into respective address location from 0x00 to 0x03; page 0x10
& 0x11).
22/33
STLED316S Commands
8.4 Display memory
The display memory stores the display data and sends to the LED when the display is on.
The address pointer, memory page and write signal indicates to this block the location to
write the data. This block will manage the address pointer. When the user writes a first byte,
the address increments by one if in auto-increment mode, else the address pointer remains
in the same location. The initial address is latched during the write/read command into the
address pointer. The display memory (7-segment/LED) is directly mapped into the display
segments. The user can access only one bank at a time in both the read and write modes.
The memory block is split into 4 pages.
Table 16. Memory page address
Page 1
7 segment memory
Addr 0x00 to 0x05
(40 bit)
Page 2
LED Display
Addr 0x00
(8 bit)
7-segment display memory page 0x00:
Table 17. 7-segment display address
Address Data
0x00 0x00
0x01 0x00
0x02 0x00
0x03 0x00
0x04 0x00
0x05 0x00
LED display memory page 0x01:
Table 18. LED display address
Address Data
Page 3
7 segment brightness
setting
Addr 0x00 to 0x03
(32bit)
Page 4
LED brightness setting
A dd r 0x 0 0 t o 0x 0 3
(32bit)
0x00h 0x00h
Initial memory:
Default memory value is “00” in all locations.
During operation:
User defined value in these locations.
When the user wants to read the data from a particular location, the user sends the address
page through read command and chooses the mode of the address pointer (fixed or auto).
In this case, the user can access the whole memory area in that particular page (maximum
0 x 05).
23/33
Commands STLED316S
The display RAM stores the data transmitted from an external device to the STLED316S
through the serial interface; addresses are as follows, in 8-bits unit:
Seg1 Seg4 Seg8
00 H
L
01 H
L
02 H
L
03 H
L
04 H
L
05 H
L
00 H
01 H
02 H
03 H
04 H
05 H
U
U
U
U
U
U
b0 b3 b4 b7
XX H
L
XX H
U
“0” in memory means GND on output; “1” in memory means VCC on output.
DIG2
DIG3
DIG4
DIG5
DIG6
DIG7
24/33
STLED316S Key-scanning and display timing
9 Key-scanning and display timing
During the first cycle, the 16 channels are used for the keyscan. The keyscan duration is
made up of 64 µs. The second cycle is used for the display of the LED (discrete). The
maximum time is 512µs and the 3
number of cycles will increase or decrease depending upon the user configuration.
rd-8th
cycles are used for the 7-segment display. The
By default, the configuration is made up of 4 cycles. If any data is written to the discrete
LED, only then the 2
This is a continuous operation. During the normal operation, the user cannot control or stop
the timing generation.
One cycle of key scanning consists of one frame, and data of 8 x 2 matrices are stored in
the RAM.
nd
cycle is valid. Otherwise the 7-segment moves from 2nd-7th cycle.
25/33
Key-scanning and display timing STLED316S
9.1 Serial communication format (reception)
The figure below shows the “reception” by STLED316S for command/data write sequence.
The STB must be low for 1 µs before the first and last clock rise. The minimum time the STB
must remain low is 9 µs.
The maximum clock frequency is 1 MHz with a duty cycle of 50%. Data set-up and hold time
must be 100 ns.
Figure 5. Serial communication format (reception)
If data are contiguous
STB
D
IN
CLK
b1b0 b2 b6 b7
23
CS15561
26/33
STLED316S Key-scanning and display timing
9.2 Serial communication format (transmission)
The figure below shows the “transmission” from STLED316S for data read sequence.
Figure 6. Serial communication format (transmission)
If data are contiguous
STB
D
IN
CLK
b1b0 b2 b6 b7
23
CS15561
Because the DIN/DOUT pin in a bi-directional pin, it is recommended to connect an external
pull-up resistor to this pin (1 KΩ to 10 KΩ).
Note: No minimum wait time is needed to read the data from the device. The STLED316S will
output the data about 250 ns after the 8
that the host must release the bus within 100ns after clocking the last bit on the 8
th
clock pulse’s falling edge. It is therefore suggested
th
clock
pulse. The STLED316S is able to clock out the valid data on the immediate falling edge of
the CLK without missing any clock cycle.
27/33
Switching characteristics waveform STLED316S
10 Switching characteristics waveform
Figure 7. Switching characteristics waveform
PWSTB
STB
tCLK-STB
CLK
DIN
DOUT
PWCLK PWCLK
tSETUP tHOLD
tPZL tPLZ
t
THZ tTZH
Sn/Gn
90%
10%
CS15562
28/33
STLED316S Application information
11 Application information
11.1 Graph of ISET against RSET
Figure 8. Graph of ISET against RSET
RSET
29/33
Application information STLED316S
11.2 Power supply sequencing
Proper power-supply sequencing is advised for all CMOS devices. It is
recommended to always apply V
before applying any signals to the input/output
CC
or control pins.
11.3 Application diagram
Figure 9. STLED316S application diagram
V
CC
C1
GND
MCU
C2
R2
R1
V
CC
IRQ_N
DIN / DOUT
RSET
ISET
6
CLK
STB
STLED316S
SEG1/KS1
-SEG8/KS8
D1 D2 D3 D4 D5 D6 D7 D8
KEY1-KEY2
GND
DIG2-DIG7
DIG1_LED
LED 6-digit 7-segment (+dot-point) display panel
Table 19. Part list
Resistors Capacitors Diodes Supply V
RSET = external
resistor for current
setting
R1 = 1-10 KΩ
DIN/DOUT external
pull-up resistor
R2 = 1-10 KΩ IRQ_N
external pull-up resistor
R3-R4 = 10 KΩ external
key-matrix pull-down
resistors
R3
R4
GND
C1 = 33 µF (25V)
electrolytic
C2 = 0.01- 0.1 µF
(25 V) ceramic
Keyscan
(8 x 2 matrix)
CS00018
D1-D8 = 1N4148 VCC = 5 V ± 10%
30/33
STLED316S Package mechanical data
12 Package mechanical data
In order to meet environmental requirements, ST offers these devices in ECOPACK®
packages. These packages have a Lead-free second level interconnect. The category of
second level interconnect is marked on the package and on the inner box label, in
compliance with JEDEC Standard JESD97. The maximum ratings related to soldering
conditions are also marked on the inner box label. ECOPACK is an ST trademark.
ECOPACK specifications are available at: www.st.com.
Figure 10. SO-24 package outline
0070769C
Table 20. SO-24 package mechanical data
millimeters inches
Symbol
Min Typ Max Min Typ Max
A 2.35 2.65 0.093 0.104
A1 0.1 0.30 0.004 0.012
B 0.33 0.51 0.013 0.020
C 0.23 0.32 0.009 0.013
D 15.20 15.60 0.598 0.614
E 7.4 7.6 0.291 0.299
e 1.27 0.050
H 10.00 10.65 0.394 0.419
h 0.25 0.75 0.010 0.030
L 0.4 1.27 0.016 0.050
k0° 8° 0° 8°
ddd 0.100 0.004
31/33
Revision history STLED316S
13 Revision history
Table 21. Document revision history
Date Revision Changes
9-Jan-2008 1 Initial release.
32/33
STLED316S
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