Front panel controller/driver with standby power management
Document overview
- Manufacturer or author: STMICROELECTRONICS
- PDF pages: 39
Technical content
Datasheet sections
- 1 Functional description
- 1.1 Block diagram
- 2 Pin connections
- 2.1 Pin description
- 3 Initialization
- 3.1 Normal mode of operation
- 3.2 Receive operation
- 3.3 Transmit operation
- 3.4 Standby or power-down mode
- 3.5 IR decoding
- 3.6 Watchdog timer
- 3.6.1 Watchdog timer operation during power-up
- 3.6.2 Watchdog timer operation during power-down
- 3.6.3 Watchdog timer operation during standby
- 3.7 Flowcharts
- 4 Display RAM address and displ ay mode
- 5 Data
- 5.1 LED port
- 5.2 SW data
- 6 Commands
- 6.1 Configuration mode setting command
- 6.2 Data setting command
- 6.3 Address setting command
- 6.4 Display control and hotkey setting command
- 7 Programmable hotkeys
- 7.1 IR Remote control
- 7.2 Front panel keys
Features
■ IC front panel controller/driver ■ Timing power standby management controller ■ IC power supply from 3.3V (VDD) to –30V (VSS) ■ Integrated VFD driver and controller ■ Infrared (IR) Remote Control (RC) Decoder (Philips or NEC format) ■ Drives many display modes (12 segments/16 digits to 20 segments/8 digits) ■ High voltage outputs (VDD - 33.3V max) ■ No external resistors necessary for driver outputs (P-channel open-drain with pull-down resistor outputs) ■ Key scanning (up to 12mm x 2mm matrix) ■ LED ports (4 channels, 20mA, max) ■ Serial interface (STB, CLK, DIN, and DOUT) communication protocol ■ Dimming circuit (adjustable up to 8 steps) ■ Supports auto-increment of display digit, which lightens the load on the MCU ■ Programmable 8 hot keys for the IR remote control command ■ Programmable 8 hot keys for key scan command ■ Low power consumption in standby mode ■ 2 general-purpose input ports (SW1, SW2) ■ Available in PQFP-52 package
Description
The STFPC311 is a complete, low-cost, integrated solution for controlling and driving a front panel Vacuum Fluorescent Display (VFD). It is ideal for decreasing power consumption in standby mode by reducing the application standby current to a minimum. It also contains a built-in remote control decoder module. While in standby mode of operation, a valid key press or signal from the infrared decoder will start a proper power-up (see Figure 6 on page 13). The STFPC311 integrates a VFD controller with a driver that is run on a 1/8 to 1/16-duty factor. It consists of 12 segment output lines, 8 grid output lines, 8 shared segments/grid output drive lines, a display memory, a control circuit, and a key scan circuit. Serial data is input to the STFPC311 through the SPI interface of a microcontroller (STB, D IN, DOUT, and CLK). Additionally, this IC can support two general- purpose input switches (SW1 and SW2).
Applications
■ DVD players ■ VCD players ■ AV equipment like Home Stereo ■ POS Systems Table 1. Device summary
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Functional description STFPC311 4/39 Doc ID 12324 Rev 2
1 Functional description
The STFPC311 receives serial data from the microcontroller through the SPI interface, latches the data, and then masks the inputs from the MCU. This data consists of commands followed by data. There are 4 types of commands:
- configuration,
- data,
- address, and
- display. The STFPC311 integrates the supply standby power management functionality, remote control decoder, and a 28-bit VFD driver. Microcontrollers usually run the first two tasks. This device reduces the stand-by power consumption of the whole Front Panel application as well as the hardware by integrating the infrared (IR) remote control decoder. A dedicated supply voltage powers the STFPC311 directly from the main supply board. When power is plugged in, control of the power supply management is done using the following pins: 1. STBY , 2. IR_DATA_IN, and 3. READY . Obsolete Product(s) - Obsolete Product(s)
1.1 Block diagram
Figure 1. Block diagram
2 Pin connections
Figure 2. Connection diagram (top view PQFP-52)
2.1 Pin description
Stand-by Sequencer Flow-Chart”. See Table 6 on page 13. Table 2. Pin description 1 OSC I This is the oscillator input pin. Connect this pin to an external resistor. 2, 3 SW1, SW2 I General purpose switch input ports. 7 GND POWER Connect this pin to system GND. display cycle (maximum keyboard size is 12 x 2).
10 READY I
a pull-down resistor on this input. 1 IR_DATA_IN I Remote control input. Feeds t he IR data from photodiode to this pin. SEG12/KS12 O Segment output pins (dual function as key source). 12, 26 VSS POWER VFD outputs high voltage pull-down level. VDD--33.3V max. to SEG20/GRID9 O These pins are selectable for segment or grid driving. 35 to 37 GRID8 to GRID6 O Grid output pins. 6, 13,38 VDD POWER 3.3V ± 0.3V Core main supply voltage. 39 NC O Not used. Left unconnected. 40 to 44 GRID5 to GRID1 O Grid output pins.
45 STB I
46 CLK I Reads serial data at the rising edge, and outputs data at the falling
47 DIN I Inputs serial data at the rising edge of the shift clock, starting from the
48 DOUT O Outputs serial data at the faling edge of the shift clock, starting from the
lower bit. This is the N-channel opendrain output pin. LED3, LED4 O CMOS outputs (20mA, max).
3 Initialization
After the power is plugged in, the device will supply power to all of the components (including the host processor) by setting STBY to logic low in order to allow the host processor to program the STFPC311. Once the STBY is set to low, the watchdog timer starts to count up to 10s (10s is the default value of the watchdog timer upon power-up). When the READY is asserted within this time, it indicates that the system has booted up well. If the READY pin is not asserted (logic high) within this time (10s), the STFPC311 will put the system into standby mode again by setting STBY to logic high. If READY is detected as logic high, the watchdog timer will be turned OFF . The main processor should program the remote control hot key and initialize the other parameters of the STFPC311 in preparation for normal operation before the system goes into standby mode. After all of the STFPC311 configuration is finished, the host processor may set the READY to low so that the STFPC311 enters standby mode. The STFPC311 then sets the MUTE pin to logic high to mute the audio output as well as the STBY pin to logic high. As a consequence of this action, the main supply voltage is turned off.
3.1 Normal mode of operation
After the power is plugged in, the device will supply power to all of the components (including the host processor) by setting STBY to logic low in order to allow the host processor to program the STFPC311. Once the STBY is set to low, the watchdog timer starts to count up to 10s (10s is the default value of the watchdog timer upon power-up). When the READY is asserted within this time, it indicates that the system has booted up well. If the READY pin is not asserted (logic high) within this time (10s), the STFPC311 will put the system into standby mode again by setting STBY to logic high. If READY is detected as logic high, the watchdog timer will be turned OFF . The main processor should program the remote control hot key and initialize the other parameters of the STFPC311 in preparation for normal operation before the system goes into standby mode. After all of the STFPC311 configuration is finished, the host processor may set the READY to low so that the STFPC311 enters standby mode. The STFPC311 then sets the MUTE pin to logic high to mute the audio output as well as the STBY pin to logic high. As a consequence of this action, the main supply voltage is turned off.
3.2 Receive operation
In receive condition, the STFPC311 waits for a valid command from the MCU. The receive circuit of STFPC311 receives 8 bit serial data, latches the data and then masks the inputs from the MCU. Refer to Figure 30 on page 32 for receive timing.
3.3 Transmit operation
In transmit condition, the STFPC311 sends the 8-bit serial data (LSB transmitted first) whenever a key is pressed or IR data is received. STFPC311 transmits data on the falling edge of CLK. Refer to Figure 31 on page 32 for transmit timing. Obsolete Product(s) - Obsolete Product(s)
3.4 Standby or power-down mode
Once the STFPC311 detects the status change of the READY to a logic low or after the preset waiting time (1s to 15s) has elapsed, the STFPC311 sets the STBY pin to a logic high to turn off the power. The MUTE signal is set to high before the power is turned off. The STFPC311 always senses the level on the READY pin during normal operation.
3.5 IR decoding
Encoded IR data from photodiode is supplied to the IR_DATA_IN input pin. The data is decoded by the internal remote control decoder module of STFPC311. In standby mode, the remote control decoder recognizes a set of predefined commands (such as STANDBY , PLAY , and OPEN/CLOSE), and takes appropriate action to manage the power supply. These predefined commands are known as "hot keys" and are programmable. The decoded IR commands are passed on to the main processor through the SPI interface by sending 3 bytes of data on the D OUT pin.
3.6 Watchdog timer
The watchdog timer is used to detect an out-of-control microprocessor. The watch dog timer is implemented in the STFPC311 to detect the abnormal processor behavior or processor- hung condition. The default state of the watchdog timer is 10s when the device powers-up. It is initialized by writing to the watchdog register and can be programmed to up to 15s (4-bit watchdog timer, present in the configuration mode setting command). If the processor does not reset the timer within the specified period, the STFPC311 will put the entire system into standby mode to reset the appliance that has stopped abnormally. The action to take when the watchdog timer has reached its count is to set the Watchdog Action register. The watchdog timer can be reset by the host processor by sending a command to reset the watchdog timer. The time-out period then starts over again. If the processor needs to be reset as a result of a hung condition (signalled using the STBY output of the STFPC311), the watchdog timer uses the amount of the time-out programmed into the Watchdog Register by the user to generate an interrupt. Note: The accuracy of the timer is within ±10% the selected resolution. This depends on the value of the external bias resistor, as it determines the internal clock frequency. The watchdog function is automatically set to 10s upon power-up and the Watchdog Interrupt is cleared. This boot-up watchdog timer is used to make sure that if the host processor hangs during the first boot-up, the STFPC311 will put the system to standby mode. During the first boot-up, the watchdog timer is disabled after the first READY signal is received. Obsolete Product(s) - Obsolete Product(s)
3.6.1 Watchdog timer oper ation during power-up
Figure 3. Power-up condition Note: Watchdog timer is turned off by default upon READY assertion. proper commands through SPI bus. In this power-up condition, the watchdog timer is triggered by internal POR pulse. During power-up, the watchdog timer value is 10 s.
3.6.2 Watchdog timer oper ation during power-down
Figure 4. Power-down condition (depending on the user’s settings). reached. If the programmed count is reached, the STBY will be asserted. Caution: It is advisable not to enable the watchdog timer during normal operation.
3.6.3 Watchdog timer oper ation during standby
- When a hot-key signal is detected either from the front panel or remote control during standby, the STBY de-asserts.
- The de-assertion of the STBY triggers the watchdog timer.
- The timer value is the programmed value that is set by the user (1s-15s). If the user did not change the value before entering standby, then it remains 10s.
- Also note: that The watchdog timer is off when the STFPC311 is in the standby mode to save power.
Figure 5. Standby condition Power-on Reset signal. It is not affected by the STB pin.
3.7 Flowcharts
- Programmable from 1 to 15s.
Figure 6. Timing power standby sequencer flowchart
Figure 7. IR RC command and front panel key operation flowchart
4 Display RAM address and display mode
through the serial interface and is assigned addresses, in units of 8-bits see Table 3. Table 3. Assigned addresses
00 HL 00 HU 01 HL 01 HU 02 HL DIG1
03 HL 03 HU 04 HL 04 HU 05 HL DIG2
06 HL 06 HU 07 HL 07 HU 08 HL DIG3
09 HL 09 HU 0A HL 0A HU 0B HL DIG4
12 HL 12 HU 13 HL 13 HU 14 HL DIG7
15 HL 15 HU 16 HL 16 HU 17 HL DIG8
18 HL 18 HU 19 HL 19 HU 1A HL DIG9
21 HL 21 HU 22 HL 22 HU 23 HL DIG12
24 HL 24 HU 25 HL 25 HU 26 HL DIG13
27 HL 27 HU 28 HL 28 HU 29 HL DIG14
5 Data
5.1 LED port
first power-up, all of the LEDs are turned off. Figure 12. LED port data WRITE command order
5.2 SW data
significant bit, see Figure 13. Bits 3 through 8 of the SW data are 0. Figure 13. SW data READ command order
6 Commands
commands/data already transmitted remain valid).
6.1 Configuration mode setting command
mode is selected, nothing is performed. b) Selects the remote control protocol to use. are allowed: no action, and set STBY to (logic) high level. Figure 14. STFPC311 configuration mode setting command order Figure 15. STFPC311 configuration mode bit 3 through bit 0 settings Note: Based on bit 5 through bit 4 settings.
- Display Mode Setting: the 16-digit, 12-segment mode is selected (default: display off and key-scan on).
- Remote Control Protocol Setting: RC-5.
- Watchdog Timer Setting: Turned on with 10s. After the first command is processed by STFPC311, the watchdog timer is turned off until it is turned on by the host.
- Watchdog action: Issue Standby.
6.2 Data setting command
This command sets the data WRITE and READ modes see Figure 16. Figure 16. STFPC311 data setting command order address mode, the address command is sent once, followed by the data bytes. incremented. Upon reaching the last display memory address, the address jumps to 00H. For fixed address mode, the address command has to be sent, followed by the display data.
represented by a high-to-low transition. Whenever bit 5 is a ‘1’, the watchdog timer is reset.
6.3 Address setting command
data is ignored until a correct address is set. Figure 17. STFPC311 address setting command order
6.4 Display control and hotkey setting command
See Figure 18 and Figure 4. All hot keys are disabled. Figure 18. STFPC311 display control and hot key setting command order
Figure 19. STFPC311 address setting mode bit 3 through bit 0 settings
7 Programmable hotkeys
7.1 IR Remote control
Eight (8) commands are user programmable for hot key functions. data is only cleared when the READY is pulled low (system goes into STANDBY state).
7.2 Front panel keys
Figure 20. Programmable hot keys (only KS1 to KS4, Box FPK1) Figure 21. HOTKEY setting command address locations (8 hot keys)
- 10110000 (command+address), and
- 00010000 (hot key mask). To store (Seg2/Key1), (Seg2/Key2), and (Seg4/Key1), the following commands are sent:
- 10110000 (command+address), and
- 00110010 (hot key mask). The same commands apply to FPK2 and FPK3 programming. Note: Reading the hot key values immediately upon STBY de-assertion is recommended. If they are not read within the watchdog preset timer value, the hot key data is cleared. Obsolete Product(s) - Obsolete Product(s)
Figure 22. Recommended software flow Note: Resetting the front panel controller at ¾ of the set watchdog time is recommended.
8 Default status
8.1 Power-up default status
8.2 STANDBY status
display turns ON with previous value. Switching off the display before entering the STANDBY state is recommended. display configuration command is changed, the display is OFF . Only hot key detection can wake the system up from STANDBY condition. Table 4. Default states
2 Key-scan ON
4 Display mode 12 Seg/16Bit
5 Display address 00H
6 RC Protocol DC-5
8 Dimming 1/16 Duty factor
9 Hot Kets (IR and FP) Disabled
10 Watchdog timer 10s
9 Remote control protocols
9.1 RC-5 remote control
MSB is transmitted first see Figure 24.
- The first two Start bits (S1 and S2) are synchronization bits. For normal operation, they are always set to '11' on the transmission side. After the photo diode, there is one inversion. The data at the IR_DATA_IN of the STFPC311 is shown in Figure 25 on page 26
- The next bit is the Toggle bit. This bit is inverted each time a key on the remote control is pressed.
- Bits A1 and A5 are the Address bits. The address bits indicate the intended application that the remote control protocol is used for.
- Bits C1..C6 are the Command bits. The command bits instruct the STFPC311 as to what action is to be taken. The data representing the RC-5 protocol is sent as a byte of data which consists of a Toggle bit and a ‘0’ bit followed by 6 bits of Command data.
Figure 23. Bi-phase encoding Figure 24. RC-5 protocol frame Figure 25. RC-5 reception example
9.2 SPI interface IR data transmission
The RC data consists of RC address, start bit, toggle bit and the RC command received. the packet should be ignored. Figure 26. RC-6 protocol frame The RC data consists of RC address, start bit, toggle bit and the RC command received. the packet should be ignored.
9.3 NEC remote control
represents a logic '0' and a space that is "3t" represents a logic '1'. t = 0.56ms. The LSB is transmitted first as shown in Figure 27. Figure 27. Pulse distance modulation Figure 28. NEC protocol transmission waveforms
10 Maximum rating
Program and other relevant quality documents. Table 5. Absolute maximum rating ( T
- Derate at -9.6 mW/°C at T A = 25 °C or higher
Table 6. Recommended operating conditions (TA = -20 to +70 °C, VSS = 0 V)
10.1 Power consumption estimation
The maximum power consumption is comprised of the Vacuum Florescent Display (VFD) driver dissipation, Load Resistance (RL), LED driver dissipation, and dynamic power consumption. P MAX = VFD + RL + LED + PDYN Where,
- PMAX = maximum power consumption,
- VFD = Vacuum Florescent Display driver dissipation,
- RL = load resistance,
- LED = LED driver dissipation, and
- PDYN = dynamic power consumption. If the segment current (ISEG) = 3 mA, grid current (IGRID) = 15 mA, and the LED current = 20 mA, then: FIP = (#segments x 6) + [#grids/(#grids +1)] x 30 mW, R L dissipation = (VDD – VSS)2 ÷ 50(segment + 1 mW), LED driver dissipation = #LEDs x 20 mW, and P DYN = VDD x 5 mW. To finish this example: FIP driver dissipation = 16 x 6 + 12/13 x 30 = 124mW R L dissipation = 33.32/50 x 17 = 377 mW LED driver dissipation = 2 x 20 = 40 P DYN = 3.3 x 5 = 16.5 mW The maximum power consumption (Total) = 557.5 mW Where, V SS = –30 V, VDD = 3.3 V, and the application is in 16-segment, 12-digit mode. Obsolete Product(s) - Obsolete Product(s)
Table 7. Electrical specifications Table 8. Switching characteristics (TA = -20 to +70 °C, VDD = 3.3 V, VSS = -30 V)
12 Timing characteristics
data of 12 x 2 matrices are stored in RAM. OFF , the key scan takes place continuously. The grid is turned off during the key scan. Figure 29. Key scanning and display timing Table 9. Timing characteristics
- Refer to page on Serial Communication Format.
13 Serial communication format
OUT pin is an N-channel, open drain output pin (see Figure 31). Figure 30. Reception (command/data WRITE) Figure 31. Data transmission (data READ)
Figure 32. Switching characteristic waveforms
14 Typical application diagram
Figure 35. Typical application circuit
- ROSC = 33 kΩ ± 1% for oscillator resistor;
- R5, R6 = 10 kΩ for external keyboard pull-down resistor;
- C1 = 33 µF-25 V electrolytic;
- C2 = 0.01 ~ 0.1 µF - 25 V ceramic;
- C3 = 0.01 ~ 0.1 µF - 63 V ceramic;
- C4 = 33 µF - 63 V electrolytic;
- D1 ~ D12 = 1N4148;
- Ef = filament voltage according with the VFD specs;
- VDD = 3.3V ±10%; * VSS = down to VDD – 33.3 V VDD ROSC VDD VDD OSC STB CLK 12 x 2 KEYBOARD Ef KEY1 KEY2 SEG1/K1 S13/G16 ~ S20/G9 G1 ~ G8 VSSVSS DIN
8 Grids/Segments
8 Grids
In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK® specifications, grade definitions and product status are available at: www.st.com. ECOPACK® is an ST trademark. Obsolete Product(s) - Obsolete Product(s)
Table 10. PQFP52 - 10x10x2 mm. plastic quad flatpack, package mechanical data Figure 36. Package dimensions
Table 11. Revision history