AS3649 AMSCO
Document overview
- Manufacturer or author: Provided By digicamel.com
- PDF pages: 39
Technical content
1 General Description
can operate in flash / torch or video light modes. as a hardware torch input (programmable). temperature threshold is exceeded. voltage levels are 1.8V compliant. Figure 1. Typical Operating Circuit
2 Key Features
3 Applications
4 Pin Assignments
Figure 2. Pin Assignments (T op View)
4.1 Pin Description
Datasheet - Pin Assignments www.ams.com/AS3649 1.0-2 3 - 39 C3 SCL serial clock input for I2C interface C4 SDA serial data input/output for I2C interface (needs external pullup resistor) D1 LED_OUT2 Flash LED current source D2 LED_OUT1 Flash LED current source D3 AGND Analog ground; make a short connection between all GND balls D4 STROBE Digital input with pulldown to control strobe time for flash function 1. Final pinout subject to change - now only used to count number of pins T able 1. Pin Description for AS3649 Pin Number1 Pin Name Description
5 Absolute Maximum Ratings
maximum rating conditions for extended periods may affect device reliability. Table 2. Absolute Maximum Ratings
- Depending on actual PCB layout and PCB used measured on demoboard; for peak power dissipation during flashing see document
- P DERATE derating factor changes the total continuous power dissipation (PT) if the ambient temperature is not 70ºC. Therefore for e.g.
- Measured on AS3649 demoboard.
6 Electrical Characteristics
Table 3. Electrical Characteristics longer flash times are allowed.
Table 3. Electrical Characteristics (Continued)
VIH High Level Input Voltage Pins ON, SCL, SDA.
1.26 V VIN V
0.84 V VIN V
- To improve efficiency at low output currents, the active part of the internal switching transistor PMOS is reduced in size to 1/5 its original
size. This reduces the current required to drive the PMOS transistor and therefore improves overall efficiency at low output currents.
- The maximum current driving capability depends on supply voltage V VIN, LED forward voltage and coil peak current limit.
- Due to slope compensation of the current limit, I LIMIT changes with duty cycle - see Figure 16 on page 11.
- Accuracy defined in % of current setting and in absolute value (µA), accuracy values have to be added together
- A pulldown current of 36µA is equal to a pulldown resistor of 42k at 1.5V
- After this period, the first clock pulse is generated
- A device must internally provide a hold time of at least 300ns for the SDA signal (referred to the V
undefined region of the falling edge of SCL.
- A fast-mode device can be used in a standard-mode system, but the requirement t SU:DAT = to 250ns must then be met. This is
the SCL signal, it must output the next data bit to the SDA line tR max + tSU:DAT = 1000 + 250 = 1250ns before the SCL line is released.
6.1 Timing Diagrams
Figure 3. I2C mode Timing Diagram
7 Typical Operating Characteristics
Figure 4. DCDC Efficiency vs. VVIN Figure 5. Application Efficiency (PLED/PVIN) vs. VVIN Figure 6. Battery Current vs. VVIN Figure 7. Efficiency at low currents (298mA/100mA) Figure 8. ILED Startup (ILED_OUT=1.0A) Figure 9. I VIN, ILED Startup (ILED_OUT=800mA)
8 Detailed Description
SDA and SCL in I2C mode and includes a hardware reset input ON. device automatically enters shutdown and resets all registers by setting pin ON=0. includes several protection and safety functions.
8.1 Internal Circuit Diagram
Figure 16. Internal Circuit Diagram
8.2 Softstart / Soft ramp down
- If two LEDs are connected, it is pos sible to operate each of the two LEDs individually as the LED current can be
- The actual value of the LED current setting can be readout by the register led_current_actual (see page 31) to allow
the camera processor to adopt to the actual operating conditions.
Figure 17. Internal circuit of 4MHz/1MHz selection Note: If the voltage on VOUT1/2 exceeds VVOUTMAX, the DCDC will always skip pulses to limit the output voltage.
8.4 Protection and Faul t Detection Functions
the current sources are disabled5 by resetting mode_setting=006 and txmask_torch_mode=00.
- Set register dcdc_skip_enable (see page 28)=1 if 4MHz forced operation shall be used below this LED current.
- Efficiency compared to a 4MHz only DCDC conv erter forced to operate with minimum duty cycle.
Table 4. 4/1MHz switching and pulseskip operating modes
- If current_boost=1, freq_switch_on is set to ‘0’.
8.4.1 Overvoltage Protection
this LED is disabled, fault_ovp is set and the device continuous operation with the other LED. theless be kept below VVOUTMAX.
8.4.2 Short Circuit Protection
and the device continuous operation with the other LED. Note: In PWM operating mode (mode_setting=01b), short circuit protection is disabled. Figure 18. Short LED Detection
8.4.3 Overtemperature Protection
driver is automatically re-enabled12 once the junction temperature drops below TOVTEMP-TOVTEMPHYST.
8.4.4 TXMASK event occurred
happened (pin TXMASK/TORCH=1), the fault register bit fault_txmask (see page 28) is set.
- Applies for all faults except TXMASK event occurred
- Except for TXMASK event occurred and Overtemperature Protection
- If overvoltage is reached, but none of the low_vds compar ator(s) triggers, VOUT1/2 is still regulated below VVOUT-
- In indicator or low current PWM mode ( mode_setting (see page 26)=01) the register fault_ovp is not set under an
overvoltage conditions. The output voltage is nevertheless kept below VVOUTMAX.
- In constant voltage mode (5V generation, register bit const_v_mode=1) this fault is disabled.
- The LED short circuit protection is disabled in indicator mode (or low current mode using PWM) (mode_setting on
12.In constant voltage mode (const_v_mode=1) the DCDC will not be automatically re-enabled.
8.4.5 Flash Timeout
current sources (on pin LED_OUT1/2) are disabled (ramping down) and fault_timeout is set.
8.4.6 Supply Undervoltage Protection
8.4.7 NTC - Flash LED Overtemperature Protection
DCDC is stopped, the current sources are disabled (instantaneous) and the bit fault_ntc (see page 28) is set. heat sink and is usually specified by the LED manufacturer).
8.5 Operating Mode and Currents
Table 5. Operating Mode and Current Settings
8.5.1 Flash Current Reductions
txmask_torch_mode=01), the flash current is reduced to flash_txmask_current if TXMASK/TORCH=1. Current Reduction by VIN Measurements in Flash Mode and Diagnostic Pulse. status_uvlo is set. The timing for the reduction of the current is 2µs/LSB current change. During the flash pulse the actual used current can be readout by the register led_current_actual. iso-settings) for the subsequent flash pulse (e.g. when using a pre-flash and a main flash pulse). Figure 19. Low Voltage Current Reduction Internal Circuit
- The MSB bit of this register not used to protect the LED; therefore the maximum torch light current = 1/4 * the maximum flash current
- The low current mode is a general purpose PWM mode to drive le ss current through the LED in average, but keep the actual pulsed
maximum current is limited to 1/4 of the maximum flash current. Always keep led_current1 >= led_current2.
Figure 21. Reducing vin_low_v during main flash additionally takes into account a longer time constant of the battery for high loads and allows a very short diagnostic pulse (only 4ms). TJUNCTION measured through the AS3649 ADC).
8.5.2 Load Balancing
Figure 22. Load Balancing
8.6 Flash Strobe Timings
- Flash duration defined by register flash_timeout and flash is started immediately when this mode is selected by the I2C command (see
- Flash duration defined by register flash_timeout and flash started with a rising edge on pin STROBE (see Figure 24):
- Flash start and timing defined by the pin STROBE; the flash duration is limited by the timeout timer defined by flash_timeout (see
Figure 23. AS3649 Flash Duration Defined by flash_timeout Without Using STROBE Input
Datasheet - Detailed Description www.ams.com/AS3649 1.0-2 19 - 39
8.7 ADC
The internal ADC is used to monitor LED temperature and DIE temperature. To operate the ADC, set the adc_channel (see page 27) and start the conversion by adc_convert. When adc_convert returns to ‘0’ the result is available in register adc_result (see page 30) (Bits 9...7)and adc_result_lsbs (Bits 1...0). The DIE junction temperature measurement returns the value according to Table 6:
8.8 I 2C Serial Data Bus
The AS3649 supports the I2C bus protocol. A device that sends data onto the bus is defined as a transmitter and a device receiving data as a receiver. The device that controls the message is called a master. The devices that are controlled by the master are referred to as slaves. A master device that generates the serial clock (SCL), controls the bus access, and generates the START and STOP conditions must control the bus. The AS3649 operates as a slave on the I2C bus. Within the bus specifications a standard mode (100kHz maximum clock rate) and a fast mode (400kHz maximum clock rate) are defined. The AS3649 works in both modes. Connections to the bus are made through the open-drain I/ O lines SDA and SCL. The following bus protocol has been defined (Figure 27): Data transfer may be initiated only when the bus is not busy. During data transfer, the data line must remain stable whenever the clock line is HIGH. Changes in the data line while the clock line is HIGH are interpreted as control signals. Accordingly, the following bus conditions have been defined: Bus Not Busy. Both data and clock lines remain HIGH. Start Data Transfer. A change in the state of the data line, from HIGH to LOW, while the clock is HIGH, defines a START condition. Stop Data Transfer. A change in the state of the data line, from LOW to HIGH, while the clock line is HIGH, defines the STOP condition. T able 6. Junction T emperature Measurement ADC result Junction Temperature - ºC ADC Return Value (10bit) -30 352 -20 343 -10 334 0 325 10 316 20 306 30 297 40 287 50 278 60 268 70 259 80 249 90 239 100 229 110 219 120 209 130 199 140 189 150 179
receiver acknowledges with a ninth bit. device must generate an extra clock pulse that is associated with this acknowledge bit. slave must leave the data line HIGH to enable the master to generate the STOP condition. Figure 27. Data Transfer on I2C Serial Bus
- Data transfer from a master transmitter to a slave receiver. The first byte transmitted by the master is the slave address. Next
significant bit (MSB) first.
- Data transfer from a slave transmitter to a master receiver. The master transmits the first byte (the slave address). The slave then
repeated START condition. Since a repeated START condition is also the beginning of the next serial transfer, the bus is not released. Data is transferred with the most significant bit (MSB) first.
- Slave Receiver Mode (Write Mode): Serial data and clock are received through SDA and SCL. After each byte is received an
Figure 30. Data Read (Write Pointer, Then Read) - Slave Receive and Transmit
8.9 Register Description
Table 7. ChipID Register Table 8. Current Set LED1 Register
- Only use current_boost=1 for currents > 1000mA(code >= CCh)
Table 9. Current Set LED2 Register
- Only use current_boost=1 for currents > 1000mA(code >= CCh)
Table 10. TXMask Register
- The MSB bit of this register not used to protect the LED; therefore the maximum current = 1/4 the maximum flash current
- If current_boost=1, the LED current is increased by 25%.
Table 11. Low Voltage / NTC Register Table 10. TXMask Register (Continued)
Table 11. Low Voltage / NTC Register (Continued)
Table 12. Flash Timer Register
- Internal calculation for codes above 20h: flash timeout [ms] = ( flash_timeout-32) * 32 + 132 [ms]
Table 13. Control Register
0 DCDC is only enabled when needed; default
1 DCDC is always enabled even when pass-though mode could be
- The two MSB bits of this register are not used to protect the LED; therefore the maximum indicator (or low current mode using PWM)
- The two MSB bits of this register not used to protect the LED; therefore the maximum torch light current = 1/4 the maximum flash cur-
Table 14. Strobe Signalling / ADC Register
000 NTC
010 VIN
Table 13. Control Register (Continued)
0 ADC conversion finished
1 Start ADC conversion - once finished the register bit is
0 Disabled - force 4MHz (1MHz) operation
1 Enabled - can use pulseskip1
0 STROBE input is edge sensitive
1 STROBE input is level sensitive
0 STROBE input disabled
1 STROBE input enabled
- Exception depending on freq_switch_on (see page 29) - see Table 4 on page 12
Table 15. Fault Register
1 Flash timeout exceeded
Table 14. Strobe Signalling / ADC Register (Continued)
1 Junction temperature limit has been exceeded
1 A shorted LED is detected (pin LED_OUT1/2)
1 An overvoltage condition is detected (pin VOUT)
- R/sC = Read, self clear; after readout the register is automatically cleared
Table 16. PWM and Indicator Register
0 Pulseskip operation is allowed depending on dcdc_skip_enable
Table 15. Fault Register (Continued)
0 Normal operation defined by mode_setting
- Using 31.5kHz modulation avoids audible noise on the output capacitor C
Table 17. ADC Result Register Table 18. ADC Result LSBs Register Table 19. Minimum LED Current Register
- Only the current through LED_OUT1 is reported.
- As the internal change of this register is asynchronous to the readout, it is recommended to readout the register after the flash pulse.
pulse for a safe operating range.
- This register is only set if an actual current reduction happens ( status_uvlo (see page 28)=1) otherwise led_current_min=0.
Table 16. PWM and Indicator Register (Continued)
Table 20. Actual LED Current Register
- Only the current through LED_OUT1 is reported.
- As the internal change of this register is asynchronous to the readout, it is recommended to readout the register twice and compare the
Table 21. Unlock Register Register Table 22. Current Boost Register
- Write 55h into register unlock (0x80) to enable access to this register (unlocking is only valid for the next I
8.10 Register Map
Table 23. Register Map1
- Always write’0’ to undefined register bits
9 Application Information
9.1 External Components
9.1.1 Input Capacitor C VIN
input decoupling and should be located as close to the device as is practical. capacitor values (C) may be used without limitations. Add a smaller capacitor in parallel to the input pin VIN (e.g. Murata GRM155R61C104, >50nF @ 3V, 0402 size).
9.1.2 Output Capacitor C VOUT
ESR and are available in small footprints. The capacitor should be located as close to the device as is practical. X5R dielectric material is recommended due to their ability to maintain capacitance over wide voltage and temperature range. If a different output capacitor is chosen, ensure similar ESR values and at least 4.2µF capacitance at 5V output voltage. Table 24. Recommended Input Capacitor Table 25. Recommended Output Capacitor
- Use only for VLED < 3.75V
9.1.3 Inductor L DCDC
the I2R power losses - high DCR values will reduce efficiency. If a different inductor is chosen, ensure similar DCR values and at least0.6µH inductance at ILIMIT.
9.1.4 Thermistor (NTC)
Flash LED Overtemperature Protection on page 14). Table 26. Recommended Inductor
- Flash pattern: 200ms/3A, 200ms pause, 200ms/3A, 2s then repeat again (no limit on the number of total cycles)
- Inductance changes by -30%, use only up to coil_peak=3.3A setting
- Use only for coil_peak=2.5A setting.
- Use only up to coil_peak=2.9A setting.
Table 27. Recommended Thermistors
9.2 PCB Layout Guideline
ground plane) - see the ‘island’ in Figure 31. Figure 31. Layout Recommendation Note: If component placement rules allow, move all components close to the AS3649 to reduce the area and length of Loop1 and Loop2. ature measurement of the LEDs due to the high LED current in the main ground plane). frequency noise for the power supply of AS3649. This capacitor should be as close as possible to the AGND/VIN pins of AS3649.
Figure 32. 5V Operating Mode
Figure 33. WL-CSP16 Marking Figure 34. WL-CSP16 Package Dimensions The coplanarity of the balls is 40µm.
The devices are available as the standard products shown in Table 28. Note: All products are RoHS compliant and ams green. Table 28. Ordering Information
Datasheet - Ordering Information www.ams.com/AS3649 1.0-2 39 - 39 Copyrights Copyright © 1997-2013, ams AG, Tobelbaderstrasse 30, 8141 Unterpremstaetten, Austria-Europe. Trademarks Registered ®. All rights reserved. The material herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. All products and companies mentioned are trademarks or registered trademarks of their respective companies. Disclaimer Devices sold by ams AG are covered by the warranty and patent indemnification provisions appearing in its Term of Sale. ams AG makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding the freedom of the described devices from patent infringement. ams AG reserves the right to change specifications and prices at any time and without notice. Therefore, prior to designing this product into a system, it is necessary to check with ams AG for current information. This product is intended for use in normal commercial applications. Applications requiring extended temperature range, unusual environmental requirements, or high reliability applications, such as military, medical life-support or life-sustaining equipment are specifically not recommended without additional processing by ams AG for each application. For shipments of less than 100 parts the manufacturing flow might show deviations from the standard production flow, such as test flow or test location. The information furnished here by ams AG is believed to be correct and accurate. However, ams AG shall not be liable to recipient or any third party for any damages, including but not limited to personal injury, property damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical data herein. No obligation or liability to recipient or any third party shall arise or flow out of ams AG rendering of technical or other services. Contact Information Headquarters ams AG Tobelbaderstrasse 30 A-8141 Unterpremstaetten, Austria Tel : +43 (0) 3136 500 0 Fax : +43 (0) 3136 525 01 For Sales Offices, Distributors and Representatives, please visit: http://www.ams.com/contact