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austriamicrosystems ag is now ams ag the technical content of this austriamicrosystems datasheet is still valid. contact information: headquarters: ams ag tobelbaderstrasse 30 8141 unterpremstaetten, austria tel: +43 (0) 3136 500 0 e - mail: ams_sales @ams.com please visit our website at www.ams.com
as3687/87xm datasheet www.austriamicrosystems.com/as3687 (mlg/ptr) 1v3-4 1 - 54 1 general description the as3687/87xm is a highly-integrated cmos lighting management unit for mobile telephones, and other 1-cell li+ or 3-cell nimh powered devices. the as3687/87xm incorporates one step up dc/dc converter for white backlight leds, one low noise charge pump for indicator- or rgb- leds, led test circuit (production test of the soldered leds at the customer si te), one analog-to-digital converter, seven current sinks, a two wire serial interface, and control logic all onto a single device. output voltages and outp ut currents are fully programmable. the as3687xm has an audio input to control one or two rgb leds. the as3687/87xm is a successor to the austrimicrosystems as3689 and therefore software compatible to the as3689 (software written for the as3689 can be easily reused for the as3687/87xm). 2 key features ? high-efficiency step up dc/dc converter ? up to 25v/50ma for white leds ? programmable output voltage with external resistors and serial interface ? overvoltage protection ? high-efficiency low noise charge pump ? 1:1, 1:1.5, and 1:2 mode ? automatic up switching (can be disabled and 1:2 mode can be blocked) ? output current up to 150ma ? efficiency up to 95% ? only 4 external ca pacitors required: 2 x 500nf flying capacitors, 2 x 1f input/output capacitors ? supports lcd white backlight or rgb leds ? seven current sinks ? all seven current sinks fully programmable (8-bit) from: 0.15ma to 38.5ma (curr1, curr2, curr6, curr30, curr31, curr32, curr33) ? three current sinks are high voltage capable (curr1, curr2, curr6) ? selectively enable/disable current sinks ? internal pwm generation ? 8 bit resolution ? autonomous logarithmic up/down dimming ? led pattern generator ? autonomous driving for fun rgb leds ? support indicator leds ? 10-bit successive approximation adc ? 27s conversion time ? selectable inputs: all current sources, vbat, cp_out, dcdc_fb ? internal temp. measurement ? support for automatic led testing (open and shorted leds can be identified in-circuit) ? standby ldo always on if serial interface is on ? regulated 2.5v max. output 10ma ? 3a quiescent current ? automatic wakeup if serial interface is enabled (allows ultra low power for device shutdown) ? audio can be used to drive rgb led (as3687xm only) ? rgb color and brightness is dependent on audio input amplitude ? can drive one or two rgb leds ? wide battery supply range: 3.0 to 5.5v ? two wire serial interface control ? overcurrent and thermal protection ? small pack age wl-csp 4x5 balls 0.5mm pitch 3 application lighting-management for mobile telephones and other 1-cell li+ or 3-cell nimh powered devices. as3687/87xm flexible lighting management (charge pump, dcdc step up, seven current sinks, adc, led test, audio light) datasheet ams ag technical content still valid as3687/87xm datasheet www.austriamicrosystems.com/as3687 1v3-4 2 - 54 4 block diagram figure 1 ? application diagram of the as3687/as3687xm step up dc/dc converter c9 4.7f c7 1.5nf q1 dcdc_sns dcdc_gate dcdc_fb r2 1m ? r3 100k ? c8 15nf c6 1f r1 0.1 ? battery charge pump 1:1, 1:1.5, 1:2 150ma battery vbat c2_p c2 1f c3 500nf c2_n c1_p c4 500nf c1_n cpout d2 d3 d4 c5 1.0f curr30 curr31 curr32 current sinks each 0.15-38.25ma d6 d7 d8 d10 d9 curr1 curr2 hv current sinks each 0.15-38.25ma serial interface r4 1-10k ? vdd_i/f clk clk data references and temperature supervision c1 1f v2_5 d1 l1 10h data as3687 lighting management unit 8bit pwm generator automatic dimming and led pattern generator curr33 d5 d11 vss led test vbat zero power device wakeup adc vtemp currx dcdc d13 d12 d14 curr6 r5 as3687/ as3687xm lighting management uni t ams ag technical content still valid as3687/87xm datasheet www.austriamicrosystems.com/as3687 1v3-4 3 - 54 figure 2 ? application diagram of the as3687xm step up dc/dc converter dcdc_sns dcdc_gate dcdc_fb charge pump 1:1, 1:1.5, 1:2 150ma battery vbat c2_p c2 1f c3 500nf c2_n c1_p c4 500nf c1_n cpout c5 1.0f curr30 curr31 curr32 current sinks each 0.15-38.25ma curr1 curr2 hv current sinks each 0.15-38.25ma serial interface r4 1-10k ? vdd_i/f clk clk data references and temperature supervision c1 1f v2_5 data as3687xm lighting management unit 8bit pwm generator automatic dimming and led pattern generator vss led test vbat zero power device wakeup adc vtemp currx dcdc curr6 audio processing curr33/audio_in audio in d rgb1 d2 d3 d4 d rgb2 alternative: 2 nd audio or backlight alternative: use dcdc step up for curr1,2,6 c9 4.7f c7 1.5nf q1 dcdc_fb r2 1m ? c8 15nf c6 1f r1 0.1 ? d1 l1 10h c10 100nf ams ag technical content still valid as3687/87xm datasheet www.austriamicrosystems.com/as3687 1v3-4 4 - 54 table of contents 1 general de scripti on ............................................................................................................ ........................... 1 2 key feat ures................................................................................................................... ............................... 1 3 applicat ion ..................................................................................................................................................... 1 4 block di agram ................................................................................................................................................ 2 5 characteri stics ................................................................................................................ ............................... 5 5.1 absolute maxi mum rati ngs .................................................................................................................... 5 5.2 operating c onditio ns ........................................................................................................... ................... 5 6 typical operating characteri stics .............................................................................................. .................... 6 7 detailed functiona l descrip tion ..................................................................................................................... 8 7.1 step up dc/dc conver ter...................................................................................................................... 8 7.1.1 feedback se lection ............................................................................................................. ............ 9 7.1.2 overvoltage protection in current feedb ack m ode ......................................................................... 9 7.1.3 voltage f eedback............................................................................................................... ........... 10 7.1.4 pcb layout hints ............................................................................................................... ........... 11 7.1.5 step up regi sters .............................................................................................................. ............ 11 7.2 charge pump.................................................................................................................... .................... 13 7.2.1 charge pump m ode switch ing ..................................................................................................... .15 7.2.2 soft start..................................................................................................................... ................... 16 7.2.3 charge pump regist ers .......................................................................................................... ...... 16 7.3 current sinks .................................................................................................................. ...................... 18 7.3.1 high voltage current si nks curr1, cu rr2, curr6 .................................................................. 19 7.3.2 current sinks curr30, curr31, curr32, curr33 ................................................................. 21 7.3.3 led pattern generat or .......................................................................................................... ........ 24 7.3.4 pwm gener ator.................................................................................................................. ........... 28 7.4 led te st....................................................................................................................... ........................ 33 7.4.1 function testing for single leds connected to the charge pump ................................................ 33 7.4.2 function testing for leds connected to the step up dcdc conver ter ........................................ 34 7.5 analog-to-digital converter .................................................................................................... ............. 34 7.5.1 adc regi sters .................................................................................................................. ............. 35 7.6 audio controlled rgb leds (onl y as3687xm)..................................................................................... 3 7 7.6.1 agc............................................................................................................................ ................... 39 7.6.2 audio control regist ers........................................................................................................ ......... 41 7.7 power-on reset ................................................................................................................. .................. 42 7.7.1 reset contro l regi ster......................................................................................................... ............ 43 7.8 temperature supervi sion........................................................................................................ .............. 43 7.8.1 temperature supervi sion registers .............................................................................................. 44 7.9 serial in terface............................................................................................................... ....................... 44 7.9.1 serial interf ace feat ures ...................................................................................................... ......... 44 7.9.2 device address select ion....................................................................................................... ....... 45 7.10 operating modes ................................................................................................................ .................. 47 8 register map................................................................................................................... ............................. 48 9 external co mponents ............................................................................................................ ...................... 50 10 pinout and packagi ng ........................................................................................................... ....................... 51 10.1 pin descr iption................................................................................................................ ...................... 51 10.2 package drawings and ma rkings .................................................................................................. ....... 52 11 ordering in formati on ........................................................................................................... ......................... 53 ams ag technical content still valid as3687/87xm datasheet www.austriamicrosystems.com/as3687 1v3-4 5 - 54 5 characteristics 5.1 absolute maximum ratings stresses beyond those listed in table 1 may cause perma nent damage to the device. these are stress ratings only, and functional operation of the device at these or an y other conditions beyond t hose indicated in section 5 electrical characteristics is not implied. exposure to absolute maximum ra ting conditions for extended periods may affect device reliability. table 1 ? absolute maximum ratings symbol parameter min max unit note v in_hv 15v pins -0.3 17 v applicable for high-voltage current sink pins curr 1 ,curr 2 , curr 6 v in_mv 5v pins -0.3 7.0 v applicable for 5v pins v bat , curr 30-33 , curr 33 /audio_in, c 1_n , c 2_n , c 1_p , c 2_p , cpout, dcdc_fb, dcdc_gate, clk, data; v in_lv 3.3v pins -0.3 5.0 v applicable for 3.3v pins v 2_5 ; dcdc_sns i in input pin current -25 +25 ma at 25oc, norm: jedec 17 t strg storage temperature range -55 125 c humidity 5 85 % non-condensing -2000 2000 v all pins except curr33/audio_in v esd electrostatic discharge norm: mil 883 e method 3015 -1000 1000 v pin curr33/audio_in v cdm norm: jedec jesd 22-a115-a level a -500 500 v p t total power dissipation 0.75 w t a = 70 oc, t junc_max = 125oc t body peak body temperature 260 c t = 20 to 40s, in accordance with ipc/jedec j-std 020. 5.2 operating conditions table 2 ? operating conditions symbol parameter min typ max unit note v hv high voltage 0.0 15.0 v applicable for high-voltage current sink pins curr 1 , curr 2 and curr 6 . v bat battery voltage 3.0 3.6 5.5 v v bat v ddi/f interface supply voltage 1.5 1.8 / 2.8 5.5 v for serial interface pins. v 2_5 voltage on pin v 2_5 2.4 2.5 2.6 v internally generated t amb operating temperature range -30 25 85 c i active battery current 70 a normal operating current ? see section ?operating modes?; interface active (excluding current of the enabled blocks) i standby standby mode current 5.8 13 a current consumption in standby mode. only 2.5v regulator on, interface active i shutdown shutdown mode current 0.1 3 a interface inactive (clk and data set to 0v) ams ag technical content still valid as3687/87xm datasheet www.austriamicrosystems.com/as3687 1v3-4 6 - 54 6 typical operating characteristics note: typical conditions are measured at 25c and 3.6v (unless otherwise noted). figure 3 ? dcdc step up converter: efficiency of +15v step up to 15v vs. load current at vbat = 3.8v 65 70 75 80 85 90 0 0.01 0.02 0.03 0.04 0.05 0.06 load current [a] efficiency of dcdc [%] vout=14.2v vout=17.2v vout=22v vout=14.2v fclk=550khz figure 4 ? charge pump: efficiency vs. vbat 0 10 20 30 40 50 60 70 80 90 100 2.8 3 3.2 3.4 3.6 3.8 4 4.2 v bat [v] efficiency of cp [%] i load =150ma i load =80ma i load =40ma figure 5 ? charge pump: battery current vs. vbat 0 50 100 150 200 250 2.8 3 3.2 3.4 3.6 3.8 4 4.2 vbat[v] ibat[ma] i load =150ma i load =80ma i load =40ma figure 6 ? current sink curr1 vs. v(currx) 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 0.0 0.5 1.0 1.5 2.0 v curr1 [v] i curr1 [ma] i curr1 =2.4ma i curr1 =19.2mam i curr1 =38.25ma figure 7 ? current sink curr1 protection current 0,0 0,5 1,0 1,5 2,0 2,5 3,0 0,0 5,0 10,0 15,0 20,0 v(curr1) [v] current [ma] curr_prot1_on=0 curr_prot1_on=1 4.5ua protection current vs. voltage (curr sinks off, curr_protx_on=0/1) figure 8 ? current sink curr3x vs. vbat 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 0.0 0.5 1.0 1.5 2.0 v curr30 [v] i curr30 [ma] i curr30 =2.4ma i curr30 =19.2mam i curr30 =38.25ma ams ag technical content still valid as3687/87xm datasheet www.austriamicrosystems.com/as3687 1v3-4 7 - 54 figure 9 ? charge pump input and out put ripple 1:1.5 mode, 100ma load 250ns/div measured with battery (3.8v) on demoboard figure 10 ? charge pump input and output ripple 1:2 mode, 100ma load 250ns/div measured with battery (3.0v) on demoboard vbat, 20mv/div, ac-coupled v(cpout), 100mv/div, ac-coupled vbat, 20mv/div, ac-coupled v(cpout), 20mv/div, ac-coupled ams ag technical content still valid as3687/87xm datasheet www.austriamicrosystems.com/as3687 1v3-4 8 - 54 7 detailed functional description 7.1 step up dc/dc converter the step up dc/dc converter is a high- efficiency current mode pwm regulator , providing output voltage up to e.g. 25v/35ma or e.g. 16v/55ma. a constant switching-frequency results in a low noise on th e supply and output voltages. figure 11 ? step up dcdc converter block diagramm option: current feedback with overvoltage protection curr1 curr2 hv current sinks each 0.156-40ma curr6 step up dc/dc converter c9 4.7f c7 1.5nf q1 dcdc_sns dcdc_gate dcdc_fb r2 1m r3 100k c8 15nf c6 1f r1 battery d1 l1 10h d6 d7 d8 d10 d9 d11 d13 d12 d14 table 3 ? step up dc/dc converter parameters symbol parameter min typ max unit note ivdd quiescent current 140 a pulse skipping mode. vfb1 feedback voltage for external resistor divider 1.20 1.25 1.30 v for constant voltage control. step_up_res = 1 vfb2 feedback voltage for current sink regulation 0.4 0.5 0.6 v on curr1, curr2 or curr6 in regulation. step_up_res = 0 additional tuning current at pin dcdc_fb and overvoltage protection 0 31 a idcdc_fb accuracy of feedback current at full scale -6 6 % adjustable by software using register dcdc control1 1 a step size (0-15 a) v protect = 1.25v + i dcdc_fb * r 2 ams ag technical content still valid as3687/87xm datasheet www.austriamicrosystems.com/as3687 1v3-4 9 - 54 table 3 ? step up dc/dc converter parameters symbol parameter min typ max unit note vrsense_max 46 66 85 e.g., 0.66a for 0.1 sense resistor vrsense_max_st art 25 33 43 for fixed startup time of 500us vrsense_max_lc current limit voltage at r sense (r1) 30 43 57 mv if stepup_lowcur = 1 rsw switch resistance 1 on-resistance of external switching transistor. 0 55 at 16v output voltage. iload load current 0 35 ma at 25v output voltage. f in switching frequency 0.9 1 1.1 mhz internally trimmed. cout output capacitor 0.7 4.7 f ceramic, 20%. use nominal 4.7 f capacitors to obtain at least 0.7 f under all conditions (voltage dependance of capacitors) l inductor 7 10 13 h use inductors with small c parasitic (<100pf) to get high efficiency. t min_on minimum on time 90 140 190 ns mdc maximum duty cycle 88 91 % voltage ripple >20khz 160 mv vripple voltage ripple <20khz 40 mv cout=4.7uf,iout=0..45ma, vbat=3.0...4.2v efficiency efficiency 85 % iout=20ma,vout=17v,vbat=3.8v to ensure soft startup of the dcdc conv erter, the overcurrent limits are reduced for a fixed time after enabling the dcdc converter. the total startup time for an output voltage of e.g. 25v is less than 2ms. 7.1.1 feedback selection register 12 (dcdc control) selects the type of feedback for the step up dc/dc converter. the feedback for the dc/dc converter can be selected eith er by current sinks (curr1, curr2, curr6) or by a voltage feedback at pin dcdc_fb. if the register bit step_up_fb_auto is set, the f eedback path is automatically selected between curr1, curr2 and curr6 (the lowe st voltage of these current sinks is used). setting step_up_fb enables feedback on the pins curr 1, curr2 or curr6. the step up dc/dc converter is regulated such that the required current at the feedback path c an be supported. (bit step_up_res should be set to 0 in this configuration) note : always choose the path with the highest voltage dr op as feedback to guarantee adequate supply for the other (unregulated) paths or enable the register bit step_up_fb_auto. 7.1.2 overvoltage protection in current feedback mode the overvoltage protection in current feedback mode (step_up_fb = 01, 10 or 11 or step_up_fb_auto = 1) works as follows: only resistor r3 and c10/c11 is soldered and r4 is omitted. an internal current source (sink) is used to generate a voltage drop across the resistor r3 . if then the voltage on dcdc_fb is above 1.25v, the dcdc is momentarily disabled to avoid too high voltages on the output of the dcdc converter. the protection voltage can be calculated according to the following formula: v protect = 1.25v + i dcdc_fb * r 2 ams ag technical content still valid as3687/87xm datasheet www.austriamicrosystems.com/as3687 1v3-4 10 - 54 notes: 1. the voltage on the pin dcdc_fb is limited by an internal protection diode to vbat + one diode forward voltage (typ. 0.6v). 2. if the overvoltage protection is not used in current feedback mode, connect dcdc_fb to ground. figure 12 ? step up dc/dc converter detail diagram; opti on: regulated output current, feedback is automatically selected between curr1, curr2, curr6 (step_up_fb_auto=1); overvoltage protection is enabled (step_up_prot=1); 1mhz clock frequency (step_up_freq=0) curr1 curr2 hv current sinks each 0.156-40ma curr6 c9 4.7f c7 1.5nf q1 dcdc_sns dcdc_gate dcdc_fb r2 1m r3 100k c8 15nf c6 1f r1 battery d1 l1 10h d6 d7 d8 d10 d9 d11 d13 d12 d14 1.25v 0.5v step_up_vtuning 1.25v step_up_prot step_up_fb ramp pwm logic gate driver vrsense_max step_up_freq 1mhz 500khz clk ov_curr ov_voltage automatic feedback select (curr1,2,6) step_up_fb_auto currx on and currx_on_cp=0 1.35v 0.8v overshoot comp error ota overshoot pulse_skip v 7.1.3 voltage feedback setting bit step_up_fb = 00 enables voltage feedback at pin dcdc_fb.. the output voltage is regulated to a cons tant value, given by (bit step_up_res should be set to 1 in this configuration) u stepup_out = (r2+r3)/r3 x 1.25 + i dcdc_fb x r2 if r3 is not used, the output voltage is by (bit step_up_res should be set to 0 in this configuration): u stepup_out = 1.25 + i dcdc_fb x r2 where: u stepup_out = step up dc/dc converter output voltage. ams ag technical content still valid as3687/87xm datasheet www.austriamicrosystems.com/as3687 1v3-4 11 - 54 r2 = feedback resistor r2. r3 = feedback resistor r3. i dcdc_fb = tuning current at pin 29 (dcdc_fb); 0 to 31a. table 4 ? voltage feedback example values i vtuning u stepup_out u stepup_out a r2 = 1m , r3 not used r2 = 500k , r3 = 50k 0 - 13.75 1 - 14.25 2 - 14.75 3 - 15.25 4 - 15.75 5 6.25 16.25 6 7.25 16.75 7 8.25 17.25 8 9.25 17.75 9 10.25 18.25 10 11.25 18.75 11 12.25 19.25 12 13.25 19.75 13 14.25 20.25 14 15.25 20.75 15 16.25 21.25 ? ? ? 30 31.25 28.75 31 32.25 29.25 caution: the voltage on curr1, curr2 and curr6 must not exceed 15v ? see also section ?high voltage current sinks?. 7.1.4 pcb layout hints to ensure good emc performance of t he dcdc converter, keep its external power components c2, r2, l1, q1, d1 and c9 close together. connect the ground of c2, q1 and c9 locally together and connect this path with a single via to the main ground plane. this ensures that local high-frequency currents will not flow to the battery. 7.1.5 step up registers reg. control addr: 00 this register enables/disables the charge pump and the step up dc/dc converter bit bit name default access description 3 step_up_on 0 r/w enable the step up converter 0b = disable the step up dc/dc converter. 1b = enable the step up dc/dc converter. ams ag technical content still valid as3687/87xm datasheet www.austriamicrosystems.com/as3687 1v3-4 12 - 54 dcdc control 1 addr: 21h this register controls the step up dc/dc converter. bit bit name default access description 0 step_up_frequ 0 r/w defines the clock frequency of the step up dc/dc converter. 0 = 1 mhz 1 = 500 khz 2:1 step_up_fb 00 r/w controls the feedback sour ce if step_up_fb_auto = 0 00 = dcdc_fb enabled (external resistor divider). set step_up_fb=00 (dcdc_fb), if external pwm is enabled for curr1, curr2 or curr6 01 = curr1 feedback enabled (feedback via white leds. 10 = curr2 feedback enabled (feedback via white leds. 11 = curr6 feedback enabled (feedback via white leds. 7:3 step_up_vtuning 00000 r/w defines the tuning current at pin dcdc_fb. 00000 = 0 a 00001 = 1 a 00010 = 2 a ? 10000 = 15 a ? 11111 = 31 a dcdc control 2 addr: 22h this register controls the step up dc/ dc converter and low-voltage current sinks curr 3x . bit bit name default access description 0 step_up_res 0 r/w gain selection for step up dc/dc converter. 0 = select 0 if step up dc/dc converter is used with current feedback (curr1, curr2 , curr6) or if dcdc_fb is used with current feedback only ? only r1, c1 connected 1 = select 1 if dcdc_fb is used with external resistor divider (2 resistors). 1 skip_fast 0 r/w step up dc/dc converter output voltage at low loads, when pulse skipping is active. 0 = accurate output voltage, more ripple. 1 = elevated output voltage, less ripple. 2 step_up_prot 1 r/w step up dc/dc converter protection. 0 = no overvoltage protection. 1 = overvoltage protection on pin dcdc_fb enabled voltage limitation =1.25v on dcdc_fb 3 stepup_lowcur 1 r/w step up dc/dc converter coil current limit. 0 = normal current limit 1 = current limit reduced by approx. 33% 4 curr1_prot_on 0 r/w 0 = no overvoltage protection 1 = pull down current switched on, if voltage exceeds 13.75v, and step_up_on=1 5 curr2_prot_on 0 r/w 0 = no overvoltage protection 1 = pull down current switched on, if voltage exceeds 13.75v, and step_up_on=1 6 curr6_prot_on 0 r/w 0 = no overvoltage protection 1 = pull down current switched on, if voltage exceeds 13.75v, and step_up_on=1 7 step_up_fb_auto 0 r/w 0 = step_up_fb select the feed back of the dcdc converter 1 = the feedback is automatically chosen within the current sinks curr1, curr2 and curr6 (never dcdc_fb). ams ag technical content still valid as3687/87xm datasheet www.austriamicrosystems.com/as3687 1v3-4 13 - 54 dcdc control 2 addr: 22h this register controls the step up dc/ dc converter and low-voltage current sinks curr 3x . bit bit name default access description only those are used for this selection, which are enabled (currx_mode must not be 00) and not connected to the charge pump (currx_on_cp must be 0). don?t use automatic feedback selection together with external pwm for the current sources curr1, curr2 or curr6. 7.2 charge pump the charge pump uses two external flying capacitors c6, c7 to generate output voltages higher than the battery voltage. there are three different operat ing modes of the charge pump itself: ? 1:1 bypass mode ? battery input and output are connected by a low-impedance switch ? battery current = output current. ? 1:1.5 mode ? the output voltage is up to 1.5 times the battery vo ltage (without load), but is limited to vcpoutmax all the time ? battery current = 1.5 times output current. ? 1:2 mode ? the output voltage is up to 2 times the battery volt age (without load), but is limited to vcpoutmax all the time ? battery current = 2 times output current as the battery voltage decreases, the charge pump must be switched from 1:1 mode to 1:1.5 mode and eventually in 1:2 mode in order to provide enough supply for the current sinks. depending on the actual current the mode with best overall efficiency can be automatically or manually selected: examples: ? battery voltage = 3.7v, led dropout voltage = 3.5v. the 1:1 mode will be selected and there is 200mv drop on the current sink and on the charge pump switch. efficiency 95%. ? battery voltage = 3.5v, led dropout voltage = 3.5v. t he 1:1.5 mode will be selected and there is 1.5v drop on the current sink and 250mv on the charge pump. efficiency 66%. ? battery voltage = 3.8v, led dropout voltage = 4.5v (c amera flash). the 1:2 mode c an be selected and there is 600mv drop on the current sink and 2.5v on the charge pump. efficiency 60%. the efficiency is dependent on the led forward voltage given by: eff=(v_led*iout)/(ui n *i in ) the charge pump mode switching can be done manually or automatically with the following possible software settings: ? automatic up all modes allowed (1:1, 1:1.5, 1:2) ? start with 1:1 mode ? switch up automatically 1:1 to 1:1.5 to 1:2 ? automatic up, but only 1:1 and 1:1.5 allowed ? start with 1:1 mode ? switch up automatically only from 1:1 to 1:1.5 mode; 1:2 mode is not used ? manual ? set modes 1:1, 1:1.5, 1:2 by software ams ag technical content still valid as3687/87xm datasheet www.austriamicrosystems.com/as3687 1v3-4 14 - 54 figure 13 ? charge pump pin connections charge pump 1:1, 1:1.5, 1:2 150ma battery vbat c2_p c3 500nf c2_n c1_p c4 500nf c1_n cpout c2 1f c5 1.0f the charge pump requires the external components listed in the following table: table 5 ? charge pump external components symbol parameter min typ max unit note c 2 external decoupling capacitor 1.0 f ceramic low-esr capacitor between pins vbat and vss. c 3 , c 4 external flying capacitor (2x) 500 nf ceramic low-esr capacitor between pins c1_p and c1_n, between pins c2_p and c2_n and between vbat and vss. c 5 external storage capacitor 1.0 f ceramic low-esr capacitor between pins cp_out and vss, pins cp_out and vss. use nominal 1 f capacitors (size 0603) note: 1.) the connections of the external capacitors c2, c3, c4 and c5 should be kept as short as possible. 2.) the maximum voltage on the flying capacitors c3 and c4 is vbat table 6 ? charge pump characteristics symbol parameter min typ max unit note icpout output current continuous 0.0 150 ma depending on pcb layout vcpoutmax output voltage 5.5 v internally limited, including output ripple efficiency 60 90 % including current sink loss; icpout < 100ma. i cp1_1.5 3.4 1:1.5 mode i cp1_2 power consumption without load fclk = 1 mhz 3.8 ma 1:2 mode r cp1_1 0.57 ? 1:1 mode; v bat >= 3.5v r cp1_1.5 effective charge pump output resistance 2.65 ? 1:1.5 mode; v bat >= 3.3v ams ag technical content still valid as3687/87xm datasheet www.austriamicrosystems.com/as3687 1v3-4 15 - 54 table 6 ? charge pump characteristics symbol parameter min typ max unit note r cp1_2 (open loop, fclk = 1mhz) 3.25 ? 1:1.2 mode; v bat >= 3.1v fclk accuracy accuracy of clock frequency -10 10 % currhv_switch curr1, 2, 6 minumum voltage 0.45 v vcurr3x_switch curr30-33 minumum voltage 0.2 v if the voltage drops below this threshold, the charge pump will use the next available mode (1:1 -> 1:1.5 or 1:1.5 -> 1:2) 240 sec cp_start_debounce=0 t deb cp automatic up- switching debounce time 2000 sec after switching on cp (cp_on set to 1), if cp_start_debounce=1 7.2.1 charge pump mode switching if automatic mode switching is enabled (cp_mode_switching = 00 or cp_mode_switching = 01) the charge pump monitors the current sinks, which are connected via a led to the output cp_out. to identify these current sources (sinks), the registers cp_mode_switch1 an d cp_mode_switch2 (register bits curr30_on_cp ? curr33_on_cp, curr1_on_cp, curr2_on_cp, curr6_on_cp) should be setup before starting the charge pump (cp_on = 1). if any of the volta ge on these current sources drops below the threshold (currlv_switch, currhv_switch, curr3x_switch), the next high er mode is selected after the debounce time. to avoid switching into 1:2 mode (battery current = 2 times output current), set cp_mode_switching = 10. if the currx_on_cp=0 and the according current sink is connected to the chargepump, the current sink will be functional, but there is no up switching of the chargepump, if the voltage compliance is too low for the current sink to supply the specified current. ams ag technical content still valid as3687/87xm datasheet www.austriamicrosystems.com/as3687 1v3-4 16 - 54 figure 14 ? automatic mode switching charge pump 1:1, 1:1.5, 1:2 cpout c5 1.0f curr30 curr31 curr32 curr33 curr1 curr2 200mv (curr3x_switch) 450mv (currhv_switch) curr30_on_cp curr31_on_cp curr32_on_cp curr33_on_cp curr1_on_cp curr2_on_cp debounce mode switching 1:1 -> 1:1.5 1:1.5 -> 1:2 cp_mode<1:0> curr6 curr6_on_cp battery vbat c2_p c3 500nf c2_n c1_p c4 500nf c1_n c2 1f 7.2.2 soft start an implemented soft start mechanism reduces the inrush current. battery current is smoothed when switching the charge pump on and also at each switching condition. this precaution reduces electromagnetic radiation significantly. 7.2.3 charge pump registers reg. control addr: 00h this register enables/disables the charge pump and the step up dc/dc converter. bit bit name default access description 2 cp_on 0 r/w 0 = set charge pump into 1:1 mode (off state) unless cp_auto_on is set 1 = enable manual or autom atic mode switching ? see register cp control for actual settings ams ag technical content still valid as3687/87xm datasheet www.austriamicrosystems.com/as3687 1v3-4 17 - 54 addr: 23h cp control this register controls the charge pump. bit bit name default access description 0 cp_clk 0 r/w clock frequency selection. 0 = 1 mhz 1 = 500 khz 2:1 cp_mode 00b r/w charge pump mode (in manual mode sets this mode, in automatic mode reports the actual mode used) 00 = 1:1 mode 01 = 1:1.5 mode 10 = 1:2 mode 11 = na note: direct switching from 1:1. 5 mode into 1:2 in manual mode and vice versa is not allowed. always switch over 1:1 mode. 4:3 cp_mode_switching 00b r/w set the mode switching algorithm: 00 = automatic mode switching; 1:1, 1:1.5 and 1:2 allowed 1 01 = automatic mode switching; only 1:1 and 1:1.5 allowed 1 10 = manual mode switching; r egister cp_mode defines the actual charge pump mode used 11 = reserved 5 cp_start_debounce 0 r/w 0 = mode switching debounce timer is always 240us 1 = upon startup (cp_on set to 1) the mode switching debounce time is first started with 2ms then reduced to 240us 6 cp_auto_on 0 r/w 0 = charge pump is switched on/off with cp_on 1 = charge pump is automatical ly switched on if a current sink, which is connected to the charge pump (defined by registers cp mode switch 1 & 2) is switched on note : 1. don?t use automatic mode switch ing together with external pwm for the current sources connceted to the charge pump with less than 500us high time. cp mode switch 1 addr: 24h setup which current sinks are connected (via l eds) to the charge pump; if set to ?1? the correspond current source (sink) is used fo r automatic mode sele ction of the charge pump bit bit name default access description 0 curr30_on_cp 0 r/w 0 = current sink curr30 is not connected to charge pump 1 = current sink curr30 is connected to charge pump 1 curr31_on_cp 0 r/w 0 = current sink curr31 is not connected to charge pump 1 = current sink curr31 is connected to charge pump 2 curr32_on_cp 0 r/w 0 = current sink curr32 is not connected to charge pump 1 = current sink curr32 is connected to charge pump 3 curr33_on_cp 0 r/w 0 = current sink curr33 is not connected to charge pump 1 = current sink curr33 is connected to charge pump ams ag technical content still valid as3687/87xm datasheet www.austriamicrosystems.com/as3687 1v3-4 18 - 54 cp mode switch 2 addr: 25h setup which current sinks are connected (via l eds) to the charge pump; if set to ?1? the correspond current source (sink) is used fo r automatic mode sele ction of the charge pump bit bit name default access description 0 curr1_on_cp 0 r/w 0 = current sink curr1 is not connected to charge pump 1 = current sink curr1 is connected to charge pump 1 curr2_on_cp 0 r/w 0 = current sink curr2 is not connected to charge pump 1 = current sink curr2 is connected to charge pump 7 curr6_on_cp 0 r/w 0 = current sink curr6 is not connected to charge pump 1 = current sink curr6 is connected to charge pump curr low voltage status 1 addr: 2ah indicates the low voltage status of the curr ent sinks. if the currx_low_v bit is set, the voltage on the current sink is too low, to drive the selected output current bit bit name default access description 0 curr30_low_v 1 r 0 = voltage of current sink curr30 >curr3x_switch 1 = voltage of current sink curr30 |