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APPEB1008 User`s Manual Camera Phone Flash - Cap-XX
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1. Supercapacitor Voltage Battery Current LED Current A 1 5 Batt Current LED Current Cap Voltage During the flash pulse battery current LED current 100mA from the battery After the flash pulse the supercapacitor is recharged in 2s drawing lt LED Current All information contained herein is strictly confidential APPEB1008 User manual V1 3 23 Dec 2005 CAP XX Pty Limited 2005 Battery Current Time Seconds Page 10 of 10 Supercapacitor Voltage V
2. Soln B Charging supercapacitor from 0V 4 2 6 4 5 Supercapacitor Voltage Batt Current 0 8 poo daa Cap Voltage z 2 g 06 T 5 Battery Current 5 gt g 2 0 4 Charge pump changes mode 2 Q 3 2 a 8 3 0 2 4 7 7 7 0 5 5 10 15 20 P Fig 8 Time Seconds Soln B Flash pulse and supercap re charge 6 Fig 7 Supercapacitor Voltage z 2 m Batt Current 4 g LED Current c Cap Voltage 6 5 3 Q j During the flash pulse battery current 0 The supercapacitor a supplies the entire 2A and its voltage drops from 5 3V to 4 5V 5 l during the pulse 5 4 j After the flash pulse the supercapacitor is recharged in 3s 2 S drawing 200mA from the battery o i i 1 0 LED Current 0 5 1 Time Seconds All information contained herein is strictly confidential APPEB1008 User manual V1 3 23 Dec 2005 Page 9 of 10 CAP XX Pty Limited 2005 Supercapacitor Voltage CAP X Soln C Charging supercap from 0V Supercapacitor Voltage 5 1V Vbatt Voltage across the supercap Supercap Voltage V 0 4 lt l z The supercapacitor is intially charged in 7s o os drawing 130mA from the battery 5 rs S 0 2 z Battery Current 2 Fig 10 Time Seconds Fig 9 Soln C Flash pulse and supercap re charge
3. shows the supercapacitor voltage battery current and LED current during and after a flash pulse D6 was added to mprevent the supercapacitor discharging into the battery through U1 when U1 is disabled In the CAP XX factory setup the charge pump is disabled when Flash mode is selected When the Flash Torch is Hi M1 is turned ON which pulls U1 pind low turning off U1 In the solution B configuration this means that the battery is contributing zero current during LED Flash so the battery can provide power to transmit a GSM pulse if necessary during LED flash Alternatively the user can remove M1 This allows the charge pump to continue operating during the LED Flash so the battery is contributing 300mA to the LED current This enables a smaller supercapacitor to be used for a given flash pulse see Supercapacitor selection Note that if M1 is removed then U1 is always enabled and the stipulation above that Flash Torch should be Lo or floating on power up is no longer required With M1 removed Flash Torch can be in any state during power up Operation Solution C configuration Fig 4 shows the solution C block diagram The supercapacitor is in series with the positive terminal of the battery In this configuration only a single cell supercapacitor is required This is half the volume of the dual cell supercapacitor required for solution B and is also lower cost However the battery current LED current unlike solution B where battery curre
4. you will need to wait 10 15 secs before the supercapacitor is fully charged from OV Fig 7 shows the battery current and supercapacitor voltage when charging a GS206 0 55F Peak battery current is limited to 750mA This reduces quickly as the supercapacitor charges There is a high inrush current when the supercapacitor is at OV since until it is charged to a voltage Vin it looks like a short circuit on the output of the charge pump R11 was added to the circuit to limit this inrush current All information contained herein is strictly confidential APPEB1008 User manual V1 3 23 Dec 2005 Page 2 of 10 CAP XX Pty Limited 2005 CAP X Note that the SP6685 is only used to charge the supercapacitor so it is always in its Torch mode pin 4 Fish connected to Gnd Once the supercapacitor has been charged select Flash or Torch mode When this signal is Hi Flash mode M2 is ON which sets the current setting resistor for U2 MIC2545 R9 R10 1200 11500 110Q This sets the LED current 2A The LEDs are on while the Enable input U2 pin1 is held Hi This turns on U2 Due to the very large capacitance of the supercapacitor the flash pulse discharges the supercapacitor only a relatively small amount typically lt 1V see section On Supercapacitor Selection This means the time to re charge the supercapacitor between flash photos is short typically 2 secs This is shorter than time the LEDs require between flashes to cool down Fig 8
5. 603 R3 4 E 1206 1 2k2 5 2 0402 C9 3 du 4 gt CONS 0603 5 S a R6 1k 100k 0402 0402 gt C10 100n u2 ii 0402 Vied Si1032R R7 EN OUT 100k By Fs INS c11 R8 SC 75A 0402 4 Gnd OUT 5 7 T 7 Joon 100k R9 R10 Maw IN V7 D1 gD Ds Di 0402 150 2k2 G12 C13 PWF1 PWF1 PWF1 PWF1 0402 0402 0402 MCASt ju 1u o o N S 0603 0603 oe S11032R SC 75A Flash Torch Fig 5 APPEB1008 Configuration B supercapacitor in parallel with the LEDs All information contained herein is strictly confidential APPEB1008 User manual V1 3 23 Dec 2005 Page 7 of 10 CAP XX Pty Limited 2005 1 2 3 4 5 Mi Bat pump IF T EN Bat C1 C2 GW1xx du J 0603 R11 1 ia eel 120 4 1206 5 c9 tu CONS les 0603 R6 100k 0402 t C11 R8 L 100n 100k 0402 0402 Flash Torch Fig 6 APPEB1008 Configuration C supercapacitor in series with the battery Pgnd SP6685 Si1032R 4 SC 75A D6 1 ny 2 MBRO520L R2 100k c5 C6 0402 100n tu 0402 0603 ne 8 T 4 R4 R5 100k 910 0402 0402 A FR C10 100n u2 0402 Ay EN OUT 100k FT Flg IN 0402 ra ai R9 R10 m 150 2k2 0402 0402 Micasa M2 7 Si1032R SC 75A All information contained herein is strictly confidential APPEB1008 User manual V1 3 23 Dec 2005 CAP XX Pty Limited 2005 16 Vied YZ D1 Z D2 V7 D3 Z D4 C13 PWF1 PWF1 PWF1 PWF1 du nN N o o 0603 Page 8 of 10 CAP X
6. CAP X Lane Cove NSW 200 Fax 61 2 9420 060 ABN 28 077 080 87 APPEB1008 User s Manual Camera Phone Flash Evaluation Board WARNING Limit max duration of FLASH to no longer than 200mS or damage to LEDs may result due to LED thermal properties Allow 3 seconds between flashes APPEB1008 is a high current FLASH LED PCB that uses minimal circuitry to pre charge a supercapacitor and then discharge LEDs at high current The purpose of this PCB is to demonstrate the minimum LED driver circuit required to deliver very high power to Flash LEDs using a supercapacitor Fig 1 shows a picture of this PCB S 5 Ce 3 x Se wo 2 304 Eo 20 30 mm Fig 1a Top side APPEB1008 Fig 1b Underside APPEB1008 Referring to CAP XX Application Note 1004 this PCB can be configured either as solution B circuit diagram Fig 5 or as solution C circuit diagram Fig 6 Configuring the evaluation PCB The PCB is configured as Solution B or Solution C by making the appropriate connections on the underside when placing the supercapacitor Fig 2a shows the configuration for Solution B and Fig 2b shows the configuration for Solution C Connect these 2 pads Supercap balance terminal Connect these 2 pads Must use a dual cell supercap Balance terminal jj e Supercap ve laid our to fit either 3 S Use single cell s GW or GS type Fig 2a Solution Upereap GW type only Fig 2b So
7. arting value of Vled 5 1V or 1 2V across the supercapacitor Fig 9 shows the battery current and supercapacitor voltage when charging a GW101 0 6F Peak battery current is limited to 300mA during charging This reduces quickly as the supercapacitor charges The charge pump behaviour in Solution C is different to Solution B because Vout gt Vin always and the charge pump never sees the supercapacitor as a short circuit Like Solution B the charge pump U1 is only used to charge the supercapacitor so it is always in its Torch mode pin 4 Flsh connected to Gnd Once the supercapacitor has been charged select Flash or Torch mode When this signal is Hi Flash mode M2 is ON which sets the current setting resistor for U2 MIC2545 R9 R10 1200 1150 110Q This sets the LED current 2A Flash Torch Hi also turns ON M1 which disables the charge pump pulls U1 pin5 Lo This is done in solution C since the battery is already supplying the LED current through the supercapacitor Leaving the charge pump enabled would cause the battery to provide gt LED current with efficiency lt 100 As in Solution B the flash pulse discharges the supercapacitor only a relatively small amount so the time to re charge the supercapacitor between flash photos is short typically shorter than time the LEDs require between flashes to cool down 2 secs Fig 10 shows the supercapacitor voltage battery current and LED current during and after a flash pulse Su
8. df The LEDs are soldered onto a bus on the PCB ve and ve are shown on Fig 1a To replace them with other LEDs if required use a hot air gun to flow the solder and then replace them All information contained herein is strictly confidential APPEB1008 User manual V1 3 23 Dec 2005 Page 5 of 10 CAP XX Pty Limited 2005 CAP X Setting the supercapacitor charge voltage The charger 0 p voltage Vrg x R2 R5 R5 where Vreg 50mV 5mV This has been factory set 5 2V The charge pump internally limits the output voltage to 5 5V It is not recommended to increase the charge pump output voltage without first consulting CAP XX This voltage can be reduced by replacing one or both of R2 R5 to reduce the ratio R2 R5 R5 Setting the LED Torch current Torch current 230 R10 from the MIC2545 datasheet This is factory set to 190mA R10 12000 Replace R10 to change the Torch current Setting the LED Flash current LED current 230 R10 R9 230xR10xR9 R10 R9 This is factory set to 2 1A R9 1209 R10 R9 1099 Replace R10 and R9 to select suitable values of Torch amp Flash current All information contained herein is strictly confidential APPEB1008 User manual V1 3 23 Dec 2005 Page 6 of 10 CAP XX Pty Limited 2005 F T org MBRO0520L N C2 1uF 7 100n C4 R1 Bat 0402 GS2xx 2k2 0402 c8 R2 J1 100k c5 3 R11 0402 1uF 1 4u7 ee 2 TTT 0805 0603 if 3 am 2R2 0
9. iguration you must use a dual cell supercapacitor rated for 4 5V continuous operation which is GS2xy or GWe2xy in CAP XX part numbering 100mQ is a good starting guess for ESR There may then need to be some iteration between C amp ESR to find a suitable supercapacitor Solution C configuration example Drive 1 x Lumileds LXCL PWF1 at 0 8A for a 250msec flash pulse Namenclature is as for Solution B From the Lumileds datasheet at 0 8A the forward voltage 3 7V allow 4 1V From the Micrel datasheet the Rpson resistance lt 50mQ so the voltage drop across the MIC2545 current switch lt 40mV Therefore the min voltage at the supercap at the end of the flash pulse 4 1V 0 04V 4 14V Vout charge pump voltage is set to 5 2V therefore the total voltage drop allowed at the supercapacitor Vd 5 2V 4 14V 1 06V Assume a supercap ESR 50mQ therefore C gt 0 8A x 0 25s 1 06V 0 8Ax0 05Q 0 196F Choose GW109 C 250mF ESR 35m Allow for ESR to double so substitute 70mQ amp 250mF for ESR amp C in the expression for Vd and check the voltage drop is lt 1 06V Vd 0 8A x 70mQ 0 25s 0 25F 0 8 x 1 07 0 86 lt 1 06V Therefore choose GW109 250mF 35V Note CAP XX product bulletins for supercap selection are available at http www cap xx com products products htm Mounting the LEDs The PCB comes factory fitted with 2 x LXCL PWF1 datasheet at http www luxeon com pdfs DS49 p
10. lution C B Configuration Configuration All information contained herein is strictly confidential APPEB1008 User manual V1 3 23 Dec 2005 Page lof 10 CAP XX Pty Limited 2005 CAP X Signal Connections Red Vbatt Must be in the range 3 0 to 5 0V Black Vbatt Purple Flash Torch select Select Torch with signal low in the range OV to 0 5V or floating Select Flash with signal Hi in the range 2V to 5V must be able to source gt 50uA Connected to a 100KQ pull down resistor on the PCB Yellow LED enable Set this signal Hi in the range 2V to 5V to turn LEDs on Set this signal Lo in the range OV to 0 5V or floating to turn LEDs off Connected to a 100KQ pull down resistor on the PCB Operation Solution B configuration Fig 3 shows the solution B block diagram The supercapacitor is in parallel with the output of the charge pump and the LEDs LED Enable turns current switch ON Flash Torch select selects current level ay E Current Pump paepae Switch Balancing resistors Fig 3 Solution B Configuration Block Diagram Refer to Fig 5 the circuit diagram for the Solution B configuration of APPEB1008 C4 is the dual cell supercapacitor When power is first applied the Flash Torch select must be low or floating so that U1 SP6685 charge pump is enabled When the Flash Torch input is low or floating M1 is OFF and U1 pin 5 EN is pulled high through R6 Depending on the size of the supercapacitor
11. nt supercap charge current only and can 0 during LED Flash This configuration enables you to achieve much higher LED current for a given battery current than would be possible LED Enable turns current switch ON Flash Torch select selects current level Current Switch Single cell supercapacitor Fig 4 Solution C Configuration Block Diagram using a standard topology of a current limited boost converter or charge pump to directly drive the flash LEDs Consider a charge pump driving an LED at 70 efficiency with the LED current 800mA All information contained herein is strictly confidential APPEB1008 User manual V1 3 23 Dec 2005 Page 3 of 10 CAP XX Pty Limited 2005 CAP X Assume the LED forward voltage 4 0V and the battery voltage 3 3V Then without the supercapacitor battery current 800mA x 4 0V 3 3V 70 1 4A which is too much for the battery to comfortably deliver and still power the rest of the phone With Solution C battery current is only 800mA Refer to Fig 6 the circuit diagram for the Solution C configuration of APPEB1008 C1 is the single cell supercapacitor In the same manner as for solution B when power is first applied the Flash Torch select must be low or floating so that U1 is enabled Depending on the size of the supercapacitor you will need to wait 3 6 secs before the supercapacitor is fully charged from the battery voltage OV across the supercapacitor to the st
12. percapacitor selection The supercapacitor must have low enough ESR and sufficient C so that Vied at the end of the flash pulse is gt forward voltage of the LEDs at the flash current Supercapacitor selection will be illustrated by the following examples Solution B configuration example Drive 2 x Lumileds LXCL PWF1 in parallel at 1A each 2A total current denoted by lep for a 150msec flash pulse denoted by PWe asu From the Lumileds datasheet at 1A the forward voltage 3 8V allow 4 2V From the Micrel datasheet the Rpson resistance lt 50mQ so the voltage drop across the MIC2545 current switch lt 100mV Therefore the min voltage at the supercap at the end of the flash pulse 4 2V 0 1V 4 3V All information contained herein is strictly confidential APPEB1008 User manual V1 3 23 Dec 2005 Page 4 of 10 CAP XX Pty Limited 2005 CAP X Vout charge pump voltage is set to 5 2V therefore the total voltage drop allowed at the supercapacitor Vd 5 2V 4 3V 0 9V Supercapacitor voltage drop Vd ILep x ESR PWetasy C Or re arranging terms C gt ILep x PWetasn Vd ILepxESR Inthe above example C gt 2A x 0 15s 0 9V 2AxESR Assume a supercap ESR 100mQ then C gt 2A x 0 15s 0 9V 2Ax0 1Q 0 43F Select a supercapacitor with 1 2 the assumed ESR to allow for ageing over life CAP XX GS206 0 55F 50mQ meets the requirements Note that for Solution B conf
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