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RT9709 1 ds9709-02 april 2011 www.richtek.com integrated over voltage protection circuit general description the RT9709 is an integrated circuit (ic) optimized to protect low voltage system from abnormal high voltage input up to 28v. the ic monitors the input voltage, battery voltage and the charging current to make sure all three parameters are operated in normal range. it also monitors its own temperature and turns the mosfet off when the chip temperature exceeds 140 c. the RT9709 can support ac charger or usb charger. when the input voltage exceeds the ovp threshold, the ic turns off the mosfet within 1us to remove the power before any damage occurs. the current in the mosfet is also limited to prevent charging the battery with an excessive current. the current limit can be programmed by an external resistor between ilim and gnd. the ocp function has a 4-bit binary counter that accumulates during an ocp event. when the total count reaches 16 times, the mosfet will be turned off permanently unless the input power is recycled. the ic also monitors the battery voltage vb. when the battery voltage exceeds 4.4v and last for more than 180us the RT9709 will turn off the mosfet. the internal logic control will turn off and latch the mosfet when the battery over-voltage event reaches 16 times. features z z z z z fully integrated protection circuit for three protection variables ` ` ` ` ` user programmable ocp threshold ` ` ` ` ` input ovp less than 1us ` ` ` ` ` battery ovp z z z z z up to 30v over voltage protection z z z z z high accuracy protection threshold z z z z z high immunity of false triggering under transients z z z z z warning indication output z z z z z enable input z z z z z thermally enhanced wdfn package z z z z z rohs compliant and halogen free applications z cellular phones z digital cameras z pdas and smart phones z portable instruments marking information for marking information, contact our sales representative directly or through a richtek distributor located in your area. ordering information note : richtek products are : ` rohs compliant and compatible with the current require- ments of ipc/jedec j-std-020. ` suitable for use in snpb or pb-free soldering processes. pin configurations (top view) wdfn-10l 3x3 vin vin nc vout vout ilim vb 9 8 7 9 1 2 3 4 5 10 gnd wrn en 11 gnd wdfn-12l 4x3 11 10 9 1 2 3 4 5 12 67 8 gnd 13 vin vin nc wrn gnd nc vout vout ilim vb en nc RT9709 package type qw : wdfn-12l 4x3 (w-type) qwb : wdfn-10l 3x3 (w-type) lead plating system g : green (halogen free and pb free) ovp default : 6.8v a : 5.85v b : 6.25v
RT9709 2 ds9709-02 april 2011 www.richtek.com function block diagram pin no. wdfn-12l 4x3 wdfn-10l 3x3 pin name pin function 1, 2 1, 2 vin input power source pin. 3 3 gnd ground pin. 4 4 wrn this is an open-drain logic output that turns low when any protection event occurs. 5, 6, 12 5 nc no internal connection. 7 6 en enable input pin. pull this pin to low or leave it floating to enable the ic. force this pin to high to disable the ic. 8 7 vb battery voltage monitoring input pin. this pin is connected to the battery pack positive terminal via resistor. 9 8 ilim over-current protection threshold setting pin. connect a resistor between this pin and gnd to set the ocp threshold. 10, 11 9, 10 vout output voltage pin. output through the mosfet. 13 (expose pad) 11 (exposed pad) gnd the exposed pad must be soldered to a large pcb and connected to gnd for maximum thermal dissipation. functional pin description typical application circuit control logic driver ocp ocp seting batovp buffer otp uvlo inovp base v ref i bias v dd en logic wrn gnd vout ilim vb vin en RT9709/a/b vin vin nc wrn gnd vout vout ilim vb en vin c in charger + r vb r ilimit battery wrn en
RT9709 3 ds9709-02 april 2011 www.richtek.com electrical characteristics parameter symbol test conditions min typ max units power- on reset RT9709 4.3 -- 6.5 v RT9709a 4.3 -- 5.5 v operation voltage RT9709b v in 4.3 -- 5.9 v v in rising 2.4 2.6 2.7 v under voltage lockout threshold v uvlo hysteresis -- 100 -- mv quiescent current i q when enable, v en < 0. 4v -- 0.5 1 ma shutdown current i q_sd when disable, v en > 1.5v 30 60 100 ua protections RT9709 6.65 6.8 7.0 v RT9709a 5.65 5.85 6.0 v input ovp reference voltage RT9709b v ovp 6 6.25 6.5 v input ovp hysteresis -- 60 100 mv input ovp propagation delay v ou t = v in x 80% -- -- 1 us over current protection i ocp 0.93 1 1.07 a over current protection blanking time bt ocp -- 170 -- us to be continued recommended operating conditions (note 4) z junction temperature range ---------------------------------------------------------------------------------------- ? 40 c to 125 c z ambient temperature range ---------------------------------------------------------------------------------------- ? 40 c to 85 c absolute maximum ratings (note 1) z supply input voltage, v in -------------------------------------------------------------------------------------------- ? 0.3v to 30v z vout, vb --------------------------------------------------------------------------------------------------------------- ? 0.3v to 7v z other pins --------------------------------------------------------------------------------------------------------------- ? 0.3v to 5.5v z power dissipation, p d @ t a = 25 c wdfn-10l 3x3 --------------------------------------------------------------------------------------------------------- 1.429w wdfn-12l 4x3 --------------------------------------------------------------------------------------------------------- 1.667w z package thermal resistance (note 2) wdfn-10l 3x3, ja --------------------------------------------------------------------------------------------------- 70 c/w wdfn-10l 3x3, jc --------------------------------------------------------------------------------------------------- 7 c/w wdfn-12l 4x3, ja --------------------------------------------------------------------------------------------------- 60 c/w wdfn-12l 4x3, jc --------------------------------------------------------------------------------------------------- 7 c/w z junction temperature ------------------------------------------------------------------------------------------------- 150 c z lead temperature (soldering, 10 se c.) --------------------------------------------------------------------------- 260 c z storage temperature range ---------------------------------------------------------------------------------------- ? 65 c to 150 c z esd susceptibility (note 3) hbm (human body mode) ------------------------------------------------------------------------------------------ 3kv mm (ma chine mode) -------------------------------------------------------------------------------------------------- 250v (v in = 5v, c in = 1uf, t a = 25 c, unless otherwise specified)
RT9709 4 ds9709-02 april 2011 www.richtek.com note 1. stresses beyond those listed under ? absolute maximum ratings ? may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. note 2. ja is measured in the natural convection at t a = 25 c on a high effective four layers thermal conductivity test board of jedec 51-7 thermal measurement standard. the case position of jc is on the exposed pad of the packages. note 3. devices are esd sensitive. handling precaution is recommended. note 4. the device is not guaranteed to function outside its operating conditions. parameter symbol test conditions min typ max units threshold 4.3 4.35 4.4 v battery over voltage protection vb ovp hysteresis -- 30 -- mv battery ovp blanking time bt ovp -- 180 -- us vb pin leakage current v vb = 4.4v -- -- 100 na rising -- 140 -- c otp threshold t sd falling -- 90 -- c logic logic-high voltage v ih 1.5 -- -- v en/ threshold logic-low voltage v il -- -- 0.4 v en/ internal pull down resistor 100 200 400 k wrn/ output logic low sink 5ma -- 0.35 0.8 v wrn output logic high leakage current -- -- 1 ua power mosfet on resistance (p-mosfet) r on1 i out = 500ma, 4.3v < v in < 6.5v -- 200 400 m
RT9709 5 ds9709-02 april 2011 www.richtek.com typical operating characteristics c in = c out = 1uf power on from v in time (2.5ms/div) wrn (2v/div) v out (5v/div) v in (5v/div) c in = c out = 1uf power off from v in time (250us/div) wrn (2v/div) v out (5v/div) v in (5v/div) i out (500ma/div) c in = c out = 1uf input ovp time (100ms/div) wrn (5v/div) v out (5v/div) v in (10v/div) i out (1a/div) battery ovp time (100ms/div) wrn (2v/div) v batt (5v/div) v acin (5v/div) i out (500ma/div) v in = 5.5v, c in = c out = 1uf v in = 5.5v, c in = c out = 1uf ocp time (100ms/div) wrn (2v/div) v out (10v/div) v in (5v/div) i out (1a/div) quiescent current v s. input voltage 0 100 200 300 400 500 600 2.8 3.1 3.4 3.7 4 4.3 4.6 4.9 5.2 5.5 5.8 6.1 6.4 6.7 input voltage (v) quiescent current (ua) c in = c out = 1uf enable disable
RT9709 6 ds9709-02 april 2011 www.richtek.com ocp threshold vs. temperature 0.95 0.97 0.99 1.01 1.03 1.05 -40 -20 0 20 40 60 80 100 120 temperature ocp threshold (a) v in = 5.5v, r set = 25k , c in = c out = 1uf ( c) battery ovp threshold vs. input voltage 4.20 4.23 4.25 4.28 4.30 4.33 4.35 4.38 4.40 4.5 4.75 5 5.25 5.5 5.75 6 6.25 6.5 6.75 input voltage (v) battery ovp threshold (v) c in = c out = 1uf ocp threshold vs. inputt voltage 0.95 0.97 0.99 1.01 1.03 1.05 4.4 4.7 5 5.3 5.6 5.9 6.2 6.5 6.8 inputt voltage (v) ocp threshold (a) r set = 25k , c in = c out = 1uf en threshold voltage v s. input voltage 0.85 0.86 0.87 0.88 0.89 0.90 0.91 0.92 0.93 0.94 0.95 4.5 4.75 5 5.25 5.5 5.75 6 6.25 6.5 6.75 input voltage (v) en threshold voltage (v) c in = c out = 1uf rising falling quiescent current vs. temperature 0 100 200 300 400 500 600 700 -40 -20 0 20 40 60 80 100 120 temperature quiescent current (ua) enable current disable current v in = 5.5v, c in = c out = 1uf ( c) battery ovp threshold vs. temperature 4.20 4.23 4.25 4.28 4.30 4.33 4.35 4.38 4.40 -40 -20 0 20 40 60 80 100 120 temperature battery ovp threshold (v ) v in = 5.5v, c in = c out = 1uf ( c)
RT9709 7 ds9709-02 april 2011 www.richtek.com r ds(on) vs. input voltage 0.15 0.17 0.19 0.21 0.23 0.25 0.27 0.29 4.3 4.5 4.7 4.9 5.1 5.3 5.5 5.7 5.9 6.1 6.3 6.5 6.7 input voltage (v) r ds(on) ( ) c in = c out = 1uf r ds(on) ( ) input ovp threshold vs. temperature 6.70 6.71 6.72 6.73 6.74 6.75 6.76 6.77 6.78 6.79 6.80 -40 -20 0 20 40 60 80 100 120 temperature input ovp threshold (v) c in = c out = 1uf ( c) r ds(on) vs. temperature 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 -40 -20 0 20 40 60 80 100 120 temperature r ds(on) ( ) r ds(on) ( ) ( c) v in = 5.5v, c in = c out = 1uf
RT9709 8 ds9709-02 april 2011 www.richtek.com applications information power up the RT9709 has an input under voltage lockout (uvlo) threshold of 2.6v with a built-in hysteresis of 100mv. before the input voltage reaches the uvlo threshold, the RT9709 is off. when the input voltage is over the uvlo threshold; the RT9709 will delay for 10ms and after the 10ms delay, the soft-start will be activated. the 10ms delay allows any transients at the input during a hot insertion of the power supply to settle down before the ic starts to operate. during the soft-start transition, the RT9709 slowly turns on the internal mosfet to reduce the inrush current. enable control the RT9709 offers an enable (en) input. when the en pin is pulled to logic high (>1.5v), the RT9709 will be shut down. when the en pin is pulled to logic low (<0.4v), the RT9709 will be powered on.the en pin has an internal pull-down resistor so that leaving the en pin floating can enable the ic. warning indication output the wrn pin is an open-drain output that indicates a low signal when any protection event occurs (input ovp, output ocp, otp and battery ovp). when the protection events are released and then the wrn pin indicates a high signal. the 4-bit binary counters for the battery ovp and the ocp are reset to zero when the ic is re-enabled. over temperature protection (otp) the RT9709 monitors its own internal temperature to prevent thermal failures. the chip turns off the mosfet when the internal temperature reaches 140 c with a built-in hysteresis of 50 c. the ic will resume to normal operation until the internal temperature falls to 90 c. input over voltage protection the RT9709 monitors the input voltage to prevent the input over voltage leading to output system failures. the input ovp threshold is set to 6.8v for the RT9709. when the input voltage exceeds the threshold, the RT9709 outputs a logic signal to turn off the internal mosfet within 1us to prevent the device in the handheld system from damaging. the hysteresis of the input ovp threshold is 100mv. when the input voltage is reduced to the normal operation voltage range, the RT9709 will re-enable the mosfet. battery over voltage protection the RT9709 monitors the battery voltage by the vb pin. when the battery voltage exceeds the 4.35v battery ovp threshold, the RT9709 has a built-in 180us blanking time to prevent any transient voltage from triggering the battery ovp. if the ovp situation still exists after 180us, the internal mosfet will be turned off and the wrn pin indicates a low signal. the battery ovp threshold has a 30mv built-in hysteresis. the control logic contains a 4- bit binary counter. if the battery over voltage event occurs for consecutive 16 times, the mosfet will be turned off permanently. the ovp latch status can be reset by the en pin. selecting r vb the RT9709 monitors the battery voltage by the vb pin. the RT9709 will be turned off when the battery voltage exceeds the 4.4v battery ovp threshold. the vb pin is connected to the battery pack positive terminal via an isolation resistor (r vb ) and the resistor is an important component. the r vb determines some parameters such as battery ovp threshold error and vb pin leakage current. generally, it is necessary to decrease the r vb for reducing the battery ovp threshold error. however, this will increase the vb pin leakage current. so, it is an important issue to get a trade-off between the battery ovp threshold error and the vb pin leakage current, the allowable resistance of the r vb is 200k to 1m . over current protection (ocp) the RT9709 monitors the output current to prevent the output short or the charging of the battery with an excessive current. the ocp (over current protection) threshold can be set by the ilim pin. the RT9709 has a built-in 170us delay time to prevent any transient noise triggering from the ocp. if the ocp situation still exists for 170us, the internal mosfet will be turned off and the wrn pin indicates a low signal. when the ocp happens for consecutive 16 times, the internal mosfet will be turned off permanently unless the input power is recycled or the enable pin is toggled.
RT9709 9 ds9709-02 april 2011 www.richtek.com figure 1. derating curves for RT9709/a package ocp ilim ilim k 25000 i = = rr selecting capacitors to get the better performance of the RT9709, it is very important to select peripherally appropriate capacitors. these capacitors determine some parameters such as input inrush current and input over shoot voltage. generally, it is necessary to increase the input capacitance c in for reducing the input over shoot voltage. however, this will increase the inrush current of input. there are two scenarios that can cause the input over shoot voltage. the first one is that when the ac adapter is hot-plugged and the second one is when the RT9709 has a step-down change. the cable between the ac adapter output and the handheld system input has a parasitic inductor and resistor causing the input over shoot voltage.generally, the input over shoot voltage range is 1.5 to 2 times the input voltage. it is recommended to use 1uf c in and c out capacitance and the c in rated voltage should be at 1.5 to 2 time of the input voltage. thermal considerations for continuous operation, do not exceed absolute maximum operation junction temperature. the maximum power dissipation depends on the thermal resistance of ic package, pcb layout, the rate of surroundings airflow and temperature difference between junction to ambient. the maximum power dissipation can be calculated by following formula : p d(max) = ( t j(max) ? t a ) / ja where t j(max) is the maximum operation junction temperature 125 c, t a is the ambient temperature and the ja is the junction to ambient thermal resistance. for recommended operating conditions specification of RT9709, where t j(max) is the maximum junction temperature of the die (125 c) and t a is the maximum ambient temperature. the junction to ambient thermal resistance ja is layout dependent. the thermal resistance ja for the wdfn-12l 4x3 packages is 60 c/w and the wdfn-10l 3x3 packages is 70 c/w on the standard jedec 51-7 four layers thermal test board. the maximum power dissipation at t a = 25 c can be calculated by following formula : p d(max) =(125 c ? 25 c) / (60 c/w) = 1.429w for wdfn 3x3 packages p d(max) =(125 c ? 25 c) / (60 c/w) = 1.667w for wdfn 4x3 packages the maximum power dissipation depends on operating ambient temperature for fixed t j(max) and thermal resistance ja . for the RT9709 packages, the figure 1 of derating curves allows the designer to see the effect of rising ambient temperature on the maximum power allowed. ocp (over current protection) setting the ocp (over current protection) threshold can be set by the ilim pin. the resistor is connected between the ilim pin and gnd to set the ocp threshold. the ocp threshold can be calculated using the following equation : 0 0.3 0.6 0.9 1.2 1.5 1.8 0 25 50 75 100 125 ambient temperature (c) maximum power dissipation (w) wdfn-10l 3x3 four layers pcb wdfn-12l 4x3 ( c) layout consideration the RT9709 is a protection device. so, a careful pcb layout is necessary. for best performance, place all peripheral components as close to the ic as possible. ` place c in , c out , r vb , and r ilim near to vin, vout, vb, ilim and gnd pin respectively. a short connection is highly recommended. the following guidelines should be strictly followed when designing a pcb layout for the RT9709. ` the exposed pad, gnd, must be soldered to a large ground plane for heat sinking and noise prevention. the through-hole vias located at the exposed pad is connected to ground plane of internal layer.
RT9709 10 ds9709-02 april 2011 www.richtek.com figure 2. recommended pcb layout ` vin traces should be wide enough to minimize inductance and handle the high currents. the trace running from input to chip should be placed carefully and shielded strictly. ` input and output capacitors must be placed close to the part. the connection between pins and capacitor pads should be copper traces without any through-hole via connection. vin vin nc vout vout ilim vb 9 8 7 9 1 2 3 4 5 10 gnd wrn en 11 gnd c out gnd gnd c in r ilim r vb output capacitor must be placed between gnd and v out to reduce noise. output capacitor must be placed between gnd and v in to reduce noise. the exposed pad and gnd should be connected to a strong ground plane for heat sinking and noise prevention .
RT9709 11 ds9709-02 april 2011 www.richtek.com outline dimension dimensions in millimeters dimensions in inches symbol min max min max a 0.700 0.800 0.028 0.031 a1 0.000 0.050 0.000 0.002 a3 0.175 0.250 0.007 0.010 b 0.180 0.300 0.007 0.012 d 2.950 3.050 0.116 0.120 d2 2.300 2.650 0.091 0.104 e 2.950 3.050 0.116 0.120 e2 1.500 1.750 0.059 0.069 e 0.500 0.020 l 0.350 0.450 0.014 0.018 w-type 10l dfn 3x3 package 1 1 2 2 note : the configuration of the pin #1 identifier is optional, but must be located within the zone indicated. det ail a pin #1 id and tie bar mark options d 1 e a3 a a1 d2 e2 l b e see detail a
RT9709 12 ds9709-02 april 2011 www.richtek.com richtek technology corporation headquarter 5f, no. 20, taiyuen street, chupei city hsinchu, taiwan, r.o.c. tel: (8863)5526789 fax: (8863)5526611 richtek technology corporation taipei office (marketing) 5f, no. 95, minchiuan road, hsintien city taipei county, taiwan, r.o.c. tel: (8862)86672399 fax: (8862)86672377 email: marketing@richtek.com information that is provided by richtek technology corporation is believed to be accurate and reliable. richtek reserves the ri ght to make any change in circuit design, specification or other related things if necessary without notice at any time. no third party intellectual property infringemen t of the applications should be guaranteed by users when integrating richtek products into any application. no legal responsibility for any said applications is assumed b y richtek. symbol dimensions in millimeters dimensions in inches min max min max a 0.700 0.800 0.028 0.031 a1 0.000 0.050 0.000 0.002 a3 0.175 0.250 0.007 0.010 b 0.180 0.300 0.007 0.012 d 3.950 4.050 0.156 0.159 d2 3.250 3.350 0.128 0.132 e 2.950 3.050 0.116 0.120 e2 1.650 1.750 0.065 0.069 e 0.500 0.020 l 0.350 0.450 0.014 0.018 w-type 12l dfn 4x3 package 1 1 2 2 note : the configuration of the pin #1 identifier is optional, but must be located within the zone indicated. det ail a pin #1 id and tie bar mark options

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