What the Designer Should Know Introduction to Automotive Linear Voltage Regulators Issue 2014 www.infineon.com/voltage-regulator Product Family Portfolio New easy to use Selection Tool www.infineon.com/vreg-finder All products are Automotive qualified and RoHS compliant 2 Content Portfolio, Key Features, Key Benefits 4 Infineon’s Automotive Linear Voltage Regulators 6 Why do we need linear voltage regulators? 7 How does a linear voltage regulator work? 7 Different types of pass element 7 Adjustable output voltage 8 Embedded Protection 9 Thermal shutdown 9 Overvoltage 9 Current limitation 10 Safe operating area 10 Reverse polarity 10 Feature Description 13 Reset 13 Watchdog 15 Enable 19 Early warning 20 Application Details 21 Thermal considerations 21 Choice of output capacitance 23 Design of input protection 24 Drop-out voltage and tracking area 25 Load transients 26 Overshoot at start-up 27 PCB layout 28 Application Schematic 29 Packages 30 Glossary 31 3 Linear Voltage Regulators Linear Voltage Regulator Multiple output regulators Quiescent current < 180µA Yes TLE4470 TLE4471 TLE4473 TLE4476 TLE7469 No Enable Enable Yes No No Yes Reset Reset Yes No No TLE7273-22) TLE7278-2 Yes TLE42994GM/E TLE4699 TLE7279-2 Reset Yes TLE7272-2 Yes TLE42364 TLE42344 TLE4284 TLE42901) Yes Watchdog No TLE4268 TLE4278 Early warning No No Watchdog No TLE4678 TLE4678-23) Early warning Yes No Watchdog Watchdog Yes Reset No TLE42644 TLE42744 TLE4294 TLE7274-2 TLF805113) TLE42664 TLE42764/76-2 TLE4286 TLE4296/-2 TLE7276-2 Yes Yes TLE4263/-2 TLE4271-2 TLE42913) Early warning Yes No Yes No TLE42994G TLE42754 TLE4285 TLE42951) TLE4675 TLE7270-2 TLE42694 TLE42794 TLF49493) TLE4270-2 No TLE4262 TLE4267 TLE4287 1) Power good 2) Window watchdog 3) New devices Selection tree Key features Standard features –– Wide operation range up to 45V –– Low dropout voltage –– Wide temperature range: -40°C up to +150°C Standard protections –– Short-circuit protection –– Reverse polarity protection as option –– Overload protection –– Overtemperature protection Enable function for main output Low quiescent current consumption in standby mode Adjustable reset function Power-on reset circuit sensing the standby voltage Standard and window watchdog Early-warning comparator for sensing input undervoltage 4 Linear Voltage Regulators High Performance Linear Voltage Regulator Infineon’s Future Linear Voltage Regulator Family 200mA Output current 500mA Enable Enable Yes No Reset No Reset Yes Yes Reset Reset No Yes No No Yes No TLS820B0 TLS820C0 TLS820A0 TLS850A0 TLS850C0 TLS850B0 Yes Watchdog Watchdog Yes No No Yes TLS820F0 TLS820D0 TLS850D0 TLS850F0 1) None contractual product proposal: for more information on product family contact sale relations Selection tree Key features Key benefits LV124 severe cranking Ultra Low Drop Voltage Suitable for very low cranking (stop and start) 3.2V Low Quiescent Current Save battery resources for ECUs in ON-state 40µA 85°C Excellent Line & Load Transient ISO2a pulse Design for harsh automotive environment 5 Linear Voltage Regulators Infineon’s Automotive Linear Voltage Regulators Supply line Stabilized voltage Input VIN e. g. car battery / battery supply Power stage Reference Protection Error amplifer Voltage regulator 6 Output VOUT Output stabilization capacitor CQ Load, e. g. microcontroller, sensor Linear Voltage Regulators Why do we need linear voltage regulators? In automotive ECUs, microcontrollers and other parts of the system have to be supplied by a stable and reliable voltage that is lower than the battery voltage (e.g. 3.3V or 5V) and works over the entire temperature range (from -40°C to 150°C). Use of discrete solutions does not manage to fulfill those conditions because of voltage dependency on loadcurrent (e.g. resistor divider) or on temperature (e.g. Zener diode). A linear voltage regulator converts a DC input voltage (e.g. battery line) into a pre-defined lower DC output voltage (e.g. 5V). In spite of input voltage variations, the output voltage remains steady and stable, as long as the input voltage is greater than the output voltage. Linear voltage regulators are the most frequently used electronic power supplies in automotive applications. Pass element Input VI Output VQ Reference Protection Error amplifer Voltage regulator Linear voltage regulator block diagram How does a linear voltage regulator work? Every linear voltage regulator consists of an internal reference voltage, an error amplifier, a feedback voltage divider and a pass transistor. The output current is delivered via the pass element controlled by the error amplifier. The error amplifier compares the reference and output feedback voltages. If the output feedback voltage is lower than the reference, the error amplifier allows more current to flow through the pass transistor, hence increasing the output voltage. On the contrary, if the feedback voltage is higher than the reference voltage, the error amplifier allows less current to flow through the pass transistor, hence decreasing the output voltage. Different types of pass element NPN linear regulators C E Conventional linear regulators use NPN bipolar transistors as the pass element. B Usually the pass element is composed of a PNP base current driver transistor and a NPN transistor single NPN power transistor, therefore the drop voltage, i.e. the minimum voltage difference between input and output, is equal to VSAT(PNP) + VBE(NPN), which is about 1.2V. Functionalities and integrated protection are limited and additional protection circuitries are required. PNP linear regulators C E With only a single PNP bipolar transistor as the pass element, the drop voltage of PNP B regulators is about 0.5V. For this reason, this type of regulator is called Low Drop Out PNP transistor (LDO). This enables it to operate during a drop in battery voltage (e.g. cranking). PNP regulators are protected against reverse polarity faults. NMOS linear regulators D S NMOS pass transistors provide very low drop-out voltage and minimal quiescent G current. A charge pump is necessary to achieve low drop-out voltage, because the NMOS gate of the NMOS needs to be ~2V higher than the voltage at source to drive the pass element open. However, the change pump also introduces additional line noise. PMOS linear regulators S D PMOS linear regulators provide very low drop-out voltage and minimal quiescent G current. An internal charge pump is not necessary for the PMOS pass element. PMOS The new control loop concept in the new Infineon PMOS linear regulators allows a faster regulation loop and better stability, requiring only a single 1µF output capacitor for stable operation. 7 Linear Voltage Regulators Adjustable output voltage The output voltage of some linear voltage regulators can be adjusted by an external resistor divider, connected to the voltage adjust pin named as ADJ or VA. Supply I Q CI LDO VDD R1 CQ MCU ADJ/VA GND R2 GND For a certain output voltage, the value of the external resistors can be easily calculated with the formula: ( R1 + R2 R2 ) Where: R2 < 50kΩ to neglect the current flowing into the ADJ/VA pin. Internal reference voltage Vref is device-dependent. The Vref value of a specific device can be found in its datasheet. If an output voltage equal to the reference voltage is needed, the output pin Q has to be directly connected to the voltage adjust pin ADJ/VA. 8 According to the datasheet Internal reference voltage Vref : typically 2.5V, Output voltage VOUT adjustable between 2.5V and 20V, Required output voltage: VOUT = 3.3V. The following resistors could be selected: R1 = 12kΩ, R2 = 39kΩ It must be taken into consideration that the accuracy of the resistors R1 and R2 adds an additional error to the output voltage tolerance. Application diagram VQ = Vref × Example: Selection of the external resistors for TLE42764GV/DV 1 I Input CI e. g. Ignition Q 5 CQ TLE42764 2 EN VA GND 3 Application diagram TLE42764GV/DV Output R1 4 Voltage adjust R2 Embedded Protections Embedded Protections Thermal shutdown Overvoltage Infineon’s automotive linear regulators are designed to withstand junction temperatures up to 150°C. Package and heat sink selections need to ensure that the maximum junction temperature is not exceeded in any operating condition. High voltage transients are generated by inductive loads (e.g. motor windings or long wire harnesses). In order to provide sufficient protection in an automotive environment, e.g. the load dump voltage, Infineon uses transistor structures withstanding a continuous supply voltage VI up to 45V. Additionally, several ICs offer protection against load dump pulses up to 65V (e.g. TLE4270, TLE4271-2). To prevent IC damage in fault conditions (e.g. output continuously short-circuited), a thermal shutdown has been integrated. The circuitry switches off the power stage for a junction temperature higher than 151°C, typically 175°C, unless otherwise specified in the datasheet. The device re-starts automatically after cooling down with a typical hysteresis of 15K (e.g. with a thermal shut-down at 175°C, re-start occurs at 160°C). Temperature above 150°C is outside the maximum ratings of the voltage regulators and reduces the IC lifetime significantly. Exceeding any of these values may damage the IC independent of pulse length. Therefore, a suppressor diode is suggested to provide protection from overvoltage. Moreover, transients can be buffered with an input capacitor that takes the entire energy or some of it, attenuating the surge at the IC input pin I. In order to protect the voltage regulator output against short circuits to the battery, the maximum voltage allowed at the output Q is much higher than the nominal output voltage. Therefore, all trackers and some voltage regulators tolerate an output voltage up to VQ = 45V, which protects them against shorts to battery at the output. Tj Tj,sd For details please refer to “Absolute Maximum Ratings” table in datasheet. Tj,sdh = 15K VI t e.g. 40V VQ Load dump transient (suppressed) VQ,nom t Thermal shutdown and hysteresis 13.5V t VQ VQ,nom t Load dump transient 9 Embedded Protections Current limitation Safe operating area In case of short-circuiting the output to GND or under excessive load conditions, the regulator is forced to deliver a very high output current. To protect the application as well as the regulator itself against damage, the IC limits the output current. Values are specified in the datasheet. In order to avoid excessive power dissipation which cannot be handled by the package, the voltage regulator decreases the maximum output current (short-circuit current) at input voltages above a certain voltage, e.g. 22V. That means that at very high input voltages, the regulator is not able to deliver the full (specified) output current. During start-up, the output capacitor is charged up with the maximum output current. Hence, the time until nominal output voltage is reached after turning on the IC or applying an input voltage is calculated as tSTARTUP = VQ × CQ/IQ,MAX. 300 IQ [mA] Two types of protection could be implemented: constant or fold-back current limitation. Infineon linear regulators use constant current limitation in order to overcome “latch-up” problems with the fold-back limiting method: If the load draws a current anywhere along the fold-back curve after the removal of the fault condition, the output will never reestablish its original voltage. 250 Tj = 25°C 200 Tj = 125°C 150 100 50 0 0 10 20 30 Maximum output current vs. input voltage (typical graph of TLE4678) 5 VQ [V] 50 VI [V] 6 4 Possible operation point after removal of fault condition 3 Constant current limitation 2 Foldback current limitation 1 0 40 0 100 200 300 400 500 Reverse polarity The following reverse polarity situations might occur in the automotive environment: Output voltage higher than input voltage (e.g. VI = 0V, VQ = 5V.) Input open, positive output voltage applied (i.e. VI = VQ). Input voltage negative, output tied to GND. IQ [mA] Current limitation Voltage regulator -II I Negative input voltage -IQ Q ESD structure CQ GND -IGND Reverse current in the voltage regulator 10 Load e.g. MCU Embedded Protections NPN bipolar voltage regulators (TLE4x8x) Linear voltage regulators with an NPN pass transistor offer no reverse polarity protection. If the input voltage is lower than the output voltage, an unlimited current will flow through parasitic junctions. Hence a blocking diode at the input is needed to withstand a steady state reverse battery condition. This series diode adds an additional drop and must be sized to hold off the system’s maximum negative voltage as well as the regulator’s maximum output current. The typical reverse currents of bipolar PNP regulators are shown in the graphs below: 20 0 VI = VQ IQ [mA] In reverse polarity situations, current may flow into the GND pin of the regulator as well as into the output pin Q. Depending on the type of the pass transistor, different protection should be applied: -20 VI = 0V -40 -60 -80 TLE4275 -100 -II Input -IQ 0 5 10 15 20 25 VQ [V] Output Series diode Typical reverse current (TLE4275) Reference 0 -IGND II [mA] -5 GND PNP bipolar voltage regulators and trackers (TLE4xxx except TLE4x8x) Regulators with PNP pass transistors allow negative supply voltage. The reverse current is limited by the PNP transistor in reverse polarity conditions. Therefore a reverse protection diode at the input is not needed. -20 -25 TLE4275 -30 -40 -32 -24 -16 -8 0 VI [V] Typical reverse current (TLE4275) -IQ Input VQ = 0V -15 Current in reverse polarity (NPN bipolar regulator) -II -10 Output The reverse voltage causes several small currents to flow into the IC, hence increasing its junction temperature. As thermal shutdown circuitry does not work in the reverse polarity condition, designers have to consider the temperature increase in their thermal design. Reference -IGND GND Current in reverse polarity (PNP bipolar regulator) 11 Embedded Protections MOSFET voltage regulators (TLE7xxx and TLF80511) Linear voltage regulators with a MOSFET (NMOS or PMOS) transistor as the pass element offer no reverse polarity protection. An unlimited reverse current would flow through the MOSFET’s reverse diode. Therefore, a series diode at the IC input is mandatory. During normal operation, it will be forward biased, adding an additional drop voltage to the system. Therefore, a Schottky diode with a low forward voltage is recommended. Input -II Regarding the Enable (Inhibit) pin, negative voltages must not be applied. Nevertheless, to allow negative transients to flow, a high-ohmic resistor can be added in series to protect the input structure. The maximum negative current must not exceed 0.5mA. e.g. Ignition Negative transient 100kΩ 100pF EN IREV > 1MΩ -IQ ESDstructure Output Series diode Charge pump Battery 47µF Reference Logic 100nF I Pulldown Voltage regulator GND -IGND Negative transients at the inhibit pin of an NMOS regulator GND Current in reverse polarity (NMOS regulator) Input -II -IQ Output Series diode Reference -IGND GND Current in reverse polarity (PMOS regulator) 12 Feature Description Feature Description Reset Supply I CQ LDO CI VDD Q RRO,ext4) RO Reset MCU Output undervoltage reset The output undervoltage reset operates by sensing the output voltage VOUT and comparing it to an internal reset threshold voltage VRT. If the output voltage drops below the reset threshold, the reset output is active low as long as the low output state exists. The reset output is typically connected to a microcontroller’s reset pin as shown in the application circuit. DT/RM/WM2) RADJ,1 D1) CD RADJ3) VQ Optional GND RADJ,2 GND 1) Only available for the voltage regulators with RESET function in TLE42xx series, TLE44xx series, TLE46xx series and TLF4949. 2) Only available for the voltage regulators with RESET function in TLE72xx series and TLE7469. The name of this pin can differ from device to device. 3) Not available for TLE4267, TLE4270-2, TLE4271-2, TLE42754, TLE4287, TLE4473, TLE4675 and TLE72xx series. 4) The external pull-up resistor is mandatory for TLE42754, TLE42794, TLE4290, TLE4473, TLE4675, as well as TLE72xx-2GV33/GV26 and TLE7469GV52/GV53, optional for all other voltage regulators with RESET function. Reset application circuit TLE42694/-2 TLE4270-2 TLE42754 TLE4278 TLE42794 TLE4287 TLE4291 TLE42994 Devices with digital reset TLE7270-2 TLE7272-2 TLE7273-2 TLE7278-2 TLE7279-2 TLE7469 TLE4290 TLE4295 Power good TLE4285 t VD VDL t VRO t trr Output undervoltage reset Devices with analog reset TLE4262 TLE4263/-2 TLE4267/-2 TLE4268 Reset headroom VRT TLE4471 TLE4473 TLE4675 TLE4678 TLE4699 TLF4949 Reset reaction time Short negative voltage spikes should not trigger an output undervoltage reset. The undervoltage reset should only be generated when the output voltage is below the reset threshold for longer than the predefined reset reaction time trr. VQ VRT t < trr VD t VDL VRO t t Reset reaction time 13 Feature Description Power-on reset delay Most control modules have a microcontroller and an accompanying clock oscillator. When the module is turned on, the clock oscillator requires a period of typically 1 to 10ms to reach a stable frequency. If the microcontroller begins operating before the oscillator is stable, the microcontroller may not initialize correctly. The power-on reset delay prevents a microcontroller from initializing while the oscillator is still stabilizing. In case a power-on reset delay time trd different from the value specified at CD = 100nF is required, the corresponding value of the delay capacitor can be calculated as follows: CD = VRT t VD VDU t VRO trd,100nF CD 100nF t × trr,d,100nF + trr,int Digital reset timing For the Infineon TLE72xx series linear voltage regulators, the power-on reset delay time trd is selectable between two predefined values through the configuration at the reset timing selection pin DT/RM/WM (see application circuit). Example: TLE7279-2 reset timing Parameter trd × 100nF Correspondingly, the reset reaction time trr can be calculated with the formula: trr = VQ trd Power-on reset delay time Symbol trd Limit values Unit Conditions 19.2 ms Fast reset timing RM = low 38.4 ms Slow reset timing RM = high Min. Typ. Max. 12.8 16 25.6 32 Power-on reset delay How to adjust reset timing? Analog reset timing For the Infineon TLE4xxx series and TLF4949 linear voltage regulators, the power-on reset delay time trd and the reset reaction time trr are determined by the delay capacitor CD connected to the D pin (see application circuit). In datasheets, the reset timing is given for a certain capacitor, e.g. 100nF. Example: TLE4291 reset timing 14 Parameter Symbol Limit values Unit Conditions Min. Typ. Max. Power-on reset delay time td,PWR,ON 8 13.5 18 ms Calculated value; CD = 100nF Internal reset reaction time trr,int – 9.0 15 µs CD = 0nF Delay capacitor discharge time trr,d – 1.9 3 µs CD = 100nF Total reset reaction time trr,total – 11.0 18 µs Calculated value; trr,d,100nF + trr,int; CD = 100nF Power good/power fail In some Infineon voltage regulators, the power good/power fail function is implemented. This functionality is similar to the reset function. In TLE4290, output voltage is supervised through a power good circuit. This function is the same as an analog reset, including delay timing set by a delay capacitance as described above for analog reset timing. In TLE4285 and TLE4295, output undervoltage is alerted by the power fail (PF) pin. As soon as VQ falls below its power fail switching threshold, its output PF is set to LOW. There is no delay pin available for connecting an external capacitor to set a reaction or delay time. In the voltage tracker TLE4254, the power good function not only alerts the undervoltage, but also the overvoltage, providing an added safety feature. Feature Description In some linear voltage regulators, RO output is internally pulled up to the output voltage. An external pull-up resistor to the output Q can be added, in case a lower-ohmic RO signal is desired. As the maximum RO sink current is limited, a minimum value of the external resistor RRO,ext is specified in the datasheet and must be adhered to. Example: TLE4291 RO internal and external pull-up resistors Parameter Symbol Limit values Min. Typ. Max. Unit Conditions Reset output external pull-up resistor to Q RRO,ext 5.6 – – kΩ 1V ≤ VQ ≤ VRT,low; VRO = 0.4V Reset output internal pull-up resistor RRO 20.0 30 40 kΩ Internally connected to Q Watchdog Supply I LDO CI Example: TLE42754 RO external pull-up resistor Parameter Reset output external pull-up resistor to VQ Symbol RRO Limit values Min. Typ. Max. 5 – – Unit Conditions kΩ 1V ≤ VQ ≤ VRT; VRO = 0.4V VDD CQ WO WI MCU RWO,ext Reset I/O WM12) WM22) D1) WADJ3) GND CD GND RWADJ 1) Only available for TLE4263-2, TLE4268, TLE4271-2, TLE4291, TLE4278, TLE4678, TLE4471, TLE4473 2) Only available for TLE7273-2, TLE7278-2, TLE7469 3) Only available for TLE4278, TLE4678 Watchdog application circuit Devices with standard watchdog TLE4263/-2 TLE4268 In some other regulators, there is no internal pull-up resistor at RO to the output voltage. For those regulators an external pull-up resistor is required. The minimum value of the required external pull-up resistor RRO is given in the datasheet. Q Optional Tips & tricks Pull-up at reset output RO The reset output RO is an open collector output requiring a pull-up resistor to a positive voltage rail (e.g. output voltage VQ). TLE4278 TLE4291 TLE4471 TLE4473 TLE4678 TLE7278-2 Devices with window watchdog TLE7273-2 TLE7469 Why do we need a watchdog? The watchdog monitors the microcontroller to ensure it is operating normally. The function of the watchdog timer is to monitor the timing of the microcontroller and reset it to a known state of operation in case of an obvious timing error. For example, a microcontroller could get stuck in a software loop and stop responding to other inputs. If too much time elapses between triggers, the watchdog senses that something is wrong and sends a reset signal to the microcontroller. VWI VWO Missing trigger pulse t t Standard watchdog 15 Feature Description VWI VWI,high VWI,low dVWI/dt Outside spec No positive VWI edge VD tWI,tr 1/fWI tWI,p t tWI,p VDW,high VDW,low Reset condition Charge/discharge curve of CD timing defined by CD tWD,low t tWD,low VWO VWO,low t Watchdog timing (analog implementation) Watchdog timing – analog implementation1) Positive edges at the watchdog input pin “WI” are expected within the watchdog trigger timeframe tWI,tr, otherwise a low signal at pin “WO” is generated and it remains low for tWD,low. All watchdog timings are defined by charging and discharging capacitor CD at pin “D”. Thus, the watchdog timing can be programmed by selecting CD. In the datasheet, reset timing is given for a certain capacitor, e.g. 100nF. Example: TLE4678 watchdog timing Parameter Symbol Limit values Unit Conditions Min. Typ. Max. Watchdog trigger time tWI,tr,100nF 25 36 47 ms Calculated value; CD = 100nF Watchdog output low time tWD,low,100nF 13 18 23 ms Calculated value; CD = 100nF VQ > VRT,low Watchdog period tWD,p,100nF 38 54 70 ms Calculated value; tWI,tr,100nF + tWD,low,100nF CD = 100nF In case a watchdog trigger time period tWI,tr different from the value specified at CD = 100nF is required, the corresponding value of the delay capacitor value can be derived as follows: CD = 100nF × tWI,tr tWI,tr,100nF Watchdog output low time tWD,low and watchdog period tWD,p can be derived using: tWD,low = tWD,low,100nF × 1) Applicable to TLE4263-2, TLE4268, TLE4271-2, TLE4291, TLE4278, TLE4678, TLE4471, TLE4473 16 tWD,p = tWI,tr + tWD,low CD 100nF Feature Description Watchdog timing – digital implementation 1) WM1 L L H H WM2 L H L H Watchdog mode Fast Slow Fast Off Reset mode Fast Slow Slow Slow The watchdog uses an internal oscillator as its time base. The watchdog time base can be adjusted using the pins WM1 and WM2. Reset Trigger during closed window Symbol Ignore window time tOW Watchdog period tWD,p Limit values No trigger during open window Ignore window Always Trigger Example: TLE7273-2 watchdog timing Parameter Always Unit Conditions Min. Typ. Max. 25.6 32 38.4 ms Fast watchdog timing 51.2 64 76.8 ms Slow watchdog timing 25.6 32 38.4 ms Fast watchdog timing 51.2 64 76.8 ms Slow watchdog timing Window watchdog 2) For safety-critical applications a more advanced watchdog called window watchdog is provided for higher security of the system. The window watchdog operates in a similar manner to the standard watchdog except a trigger must occur within a certain window or time slot. If a trigger occurs outside of the window or does not occur at all within the designated window, the window watchdog will reset the microcontroller. When an unintentional trigger occurs, the standard watchdog is not able to decipher if this trigger is valid. The window requirement enables the window watchdog to detect unintentional triggers. Closed window Open window No trigger Window watchdog Load-dependent watchdog activation If a microcontroller is set to sleep mode or to low power mode, its current consumption is very low and it might not be able to send any watchdog pulses to the voltage regulator’s watchdog input “WI”. In order to avoid unwanted wake-up signals due to missing edges at pin “WI”, the watchdog function of some linear voltage regulators can be activated dependent on the regulator’s output current. The load-dependent watchdog activation feature is available on TLE4268, TLE4278, TLE4678, TLE7273-2 and TLE7278-2. On voltage regulators TLE4268, TLE7273-2 and TLE7278-2, watchdog activation and deactivation thresholds are fixed. On voltage regulators TLE4278 and TLE4678, the watchdog can be permanently activated or deactivated, or enabled/ disabled by defining a current threshold through the external resistor at the WADJ pin: An external resistor at WADJ to GND determines the watchdog activation threshold. Connect WADJ directly to GND to permanently deactivate the watchdog. Connect WADJ to the output Q via a 270kΩ resistor to permanently activate the watchdog. 1) Applicable to TLE7273-2, TLE7278-2, TLE7469 2) The window watchdog is available for voltage regulators TLE7273-2 and TLE7469. 17 Feature Description Vi/V VQ/V VRT IQ/A VRO/V trd trr Normal operation trd trd Wnd Ingnore window WDI/V Don’t care WDI during IW 1. Long OW CW OW CW 1. Long OW OW 1. Correct trigger CW (Wrong) Trigger in CW No trigger in OW tWD,p Watchdog timing (window watchdog) Disadvantage of a standard watchdog It is possible that the microcontroller could become trapped in a routine of only emitting the pulses. The standard watchdog is not capable of detecting this potential program error and would interpret this signal as valid. The solution in this case would be to use the window watchdog. VWI VWO Unwanted trigger pulse Missing trigger pulse Window watchdog To further reduce the potential risk of program errors, a more advanced watchdog called window watchdog has been implemented. It offers higher system security. A window watchdog monitors not only the minimum pulse period, but also the maximum pulse period. A watchdog pulse must occur within a certain window or time slot. If a pulse occurs outside of the window or does not occur at all within the designated window, the window watchdog will reset the microcontroller. VWI t Standard watchdog VWO Unwanted trigger pulse t Window watchdog t t Disadvantage of standard watchdog 18 Missing trigger pulse Advantage of window watchdog Feature Description Tips & tricks Watchdog deactivation In some applications, the microcontroller software is stored in an external non-volatile memory and needs to be downloaded to the microcontroller after every start-up. During this download, the microcontroller is not able to send any watchdog pulses. To skip unwanted watchdog alerts due to missing WI-input edges, the watchdog function should be deactivated. The watchdog function can be easily deactivated by connecting WADJ directly to GND for those regulators with an adjustable watchdog activation threshold (TLE4278 and TLE4678). Enable Supply I Output Q CI CQ LDO e. g. Ignition EN/INH GND Enable application circuit Devices with enable For other linear regulators, the watchdog function could be deactivated by connecting the D pin to the output Q via a pull-up resistor to compensate the discharge current of the watchdog. The pull-up resistor can be determined by referring to the delay capacitor discharge current specified in the datasheet. Example: watchdog deactivation for TLE4263-2 Parameter Discharge current Symbol ID,wd Limit values Min. Typ. Max. 4.40 6.25 9.40 Unit Conditions µA VD = 1.0V Formula to apply: RPU,D ≤ (VQ – VD)/ID,wd,max = (5.0V – 1.0V)/9.40µA = 425kΩ Taking some headroom for tolerances, a 390kΩ pull-up resistor could be recommended for deactivating the watchdog function on the TLE4263-2. TLE42364 TLE4262 TLE4263/-2 TLE4266-2 TLE42664 TLE4267/-2 TLE4276-2 TLE42764 TLE4286 TLE4287 TLE4291 TLE4296/-2 TLE42994 TLE4471 TLE4473 TLE4476 TLE4699 TLE7272-2 TLE7273-2 TLE7276-2 TLE7278-2 TLE7279-2 TLE7469 Why do we need enable? Many linear voltage regulators can be turned off with an enable control input. In some automotive and batteryrun applications, it is necessary to significantly reduce the quiescent current when the module is off. This can be accomplished by turning off the linear voltage regulator with low-logic signal (0V) applied to the EN pin. To turn on the regulator again, a high-logic signal (e.g. 5V) is applied to the EN pin. This function is also called inhibit and the corresponding pin is called INH in some older voltage regulators. If the enable/inhibit function is not used, the EN or INH pin must be connected to the input I. Example: TLE42994 current consumption VI = 13.5V; Tj = -40°C < Tj < 150°C Parameter Symbol Limit values Min. Typ. Max. Unit Conditions Current consumption; Iq = II - IQ Iq – 65 1051) µA Enable HIGH1); IQ ≤ 1mA1); Tj < 85°C Current consumption; Iq = II - IQ Iq – – 12) µA VEN = 0V 2); Tj = 25°C 1) Though no output current is flowing, the regulator is still supplying the nominal output voltage and consumes some current. 2) The output voltage is switched off by EN/INH, the regulator consumes only very low stand-by current. 19 Feature Description Tips & tricks TLE4267 inhibit/hold function In microcontroller supply systems, enable/inhibit might be controlled by the ignition key. Microcontrollers must be able to store data in case the ignition key is turned off. The additional HOLD pin of the TLE4267 allows microcontrollers to control the turn-off sequence. The voltage regulator remains on after inhibit is turned off as long as the microcontroller keeps the HOLD pin active low. The microcontroller can then release the HOLD signal when it is ready to be switched off, and then the voltage regulator will be turned off. VBAT I Q VDD TLE4267 Ignition INH MCU HOLD I/O its start-up state when it powers up again and the reset is released. The early warning function is generally an integrated and independent comparator with a status output, which can compare any external voltage with the internal reference voltage. Besides the input voltage, this function can be used to sense any voltage rail on the board, sending a high/ low status signal to a logic-IC or a microcontroller. For this reason, this function is also called the sense function. Early warning function The early warning function monitors the input voltage by comparing a divided sample of the input voltage to a known reference voltage. When the voltage at the sense input (SI) VSI drops below the sense low threshold VSI,low an active low warning signal is generated at the sense output (SO) pin. Sense input voltage VSI,high TLE4267 inhibit/hold function VSI,low Early warning High Supply I CI Q LDO RSI1 SI RSI2 VDD CQ MCU RSO1) SO t GND GND Early warning function Devices with early warning TLE4699 TLE7469 The desired threshold voltage for the input voltage is adjustable through the external voltage divider: VI,TH = VSI × Early warning application circuit TLE7279-2 TLF4949 Why do we need early warning? The purpose of the early warning function is to alert the microcontroller that the supply voltage is dropping and a reset signal is imminent. This allows the microcontroller to perform any “house cleaning” chores like saving RAM values into EEPROM memory so it can resume operation at 20 Low I/O 1) The external pull-up resistor is mandatory for TLE42794, TLE72xx-2GV33/GV26 and TLE7469GV52/GV53, optional for all other voltage regulators with Early Warning function. TLE42694 TLE42994 t Sense output ( RSI1 + RSI2 RSI2 ) VI,TH: desired threshold triggering the early warning. VSI: given in the datasheet by VSI,low and VSI,high. Example: TLE42694 early warning thresholds Parameter Symbol Limit values Min. Typ. Max. Unit Sense threshold high VSI,high 1.24 1.31 1.38 V Sense threshold low VSI,low 1.16 1.22 1.28 V Sense switching hysteresis VSI,hy 20 90 160 mV Application Details Application Details Thermal considerations The maximum junction temperature allowed for most Infineon automotive linear voltage regulators is 150°C. The thermal shutdown protection can prevent the device from direct damage caused by an excessively high junction temperature. Moreover, exceeding the specified maximum junction temperature reduces the lifetime of the device. A proper design must ensure that the linear regulator is always working beneath the allowed maximum junction temperature as specified in the datasheet of the device. The maximum an acceptable thermal resistance RthJA can then be calculated: RthJA,max = (Tj,max – Ta)/PD Based on the above calculation the proper PCB type and the necessary heat sink area can be selected with reference to the thermal resistance table in the regulator’s datasheet. Below is an example of the thermal consideration for an application with TLE42754G. Example: TLE42754G thermal resistance Thermal resistance Thermal resistance is the temperature difference across a structure in the presence of a unit of power dissipation. It reflects to the capacity of the package to conduct heat outside the device. It is the key parameter to be considered in the thermal design. The most useful thermal resistance for thermal calculation is the junction-to-ambient thermal resistance RthJA. In most datasheets, junction-to-ambient thermal resistance RthJA is specified in accordance with JEDEC JESD51 standards defining PCB types and heat sink area. 1.5mm 70µm Cu Parameter Symbol Limit values Unit Conditions – k/W – Min. Typ. Max. 3.7 Junction to case1) RthJC – Junction to ambient RthJA – 22.0 – k/W 2) – 70.0 – k/W Footprint only 3) – 42.0 – k/W 300mm2 heatsink area on PCB 3) – 33.0 – k/W 600mm2 heatsink area on PCB 3) 1) Not subject to production test, specified by design. 2) Specified RthJA value is according to Jedec JESD51-2, -5, -7 at natural convection on FR4 2s2p board; The product (chip + package) was simulated on a 76.2 x 114.3 x 1.5 mm3 board with 2 inner copper layers (2 x 70µm Cu, 2 x 35µm Cu). Where applicable a thermal via array under the exposed pad contacted the first inner copper layer. 3) Specified RthJA value is according to JEDEC JESD 51-3 at natural convection on FR4 1s0p board; The product (chip + package) was simulated on a 76.2 x 114.3 x 1.5 mm3 board with 1 copper layer (1 x 70µm Cu). 70µm Cu 1.5mm Cross section JEDEC 1s0p board 70µm Cu 35µm Cu 35µm Cu 70µm Cu Cross section JEDEC 2s2p board Thermal calculation Knowing the input voltage, the output voltage and the load profile of the application, the total power dissipation can be calculated: PD = (VIN – VOUT) × IOUT + VIN × Iq Example: Thermal calculation for TLE42754G Application conditions: VIN = 13.5V VOUT = 5V IOUT = 200mA Ta = 85°C Determination of RthJA: PD = (VIN – VOUT) × IOUT + VIN × Iq = (13.5V – 5V) × 250mA + 13.5V × 10mA = 2.125W + 0.135W = 2.26W RthJA,max = (Tj,max – Ta)/PD = (150°C – 85°C)/2.26W = 28.76K/W As a result, the PCB design must ensure a thermal resistance RthJA lower than 28.76K/W. Referring to the thermal resistance table of the TLE42754G, only a FR4 2s2p board could be used. 21 Application Details Transient thermal resistance Thermal resistance constant RthJA reflects the steady-state condition of the power dissipation. In other words, the amount of heat generated in the junction of the device equals the heat conducted away. In some applications, the worst case conditions for power dissipation occur during the transient state. The duration in transient could be far shorter than steady-state. Thermal impedance curves characterize delta temperature rise (between junction and ambient) versus power dissipation as a function of time. In this case, the junction temperature will be a function of time: Tj(t) = ZthJA(t) × PD(t) + Ta 45 40 Zth-JA/C [K/W] 35 30 Zth-JA 1s0p with 600m2 cooling area Zth-JA 1s0p with 300m2 cooling area Zth-JA 2s2p Zth-JC,bottom Tips & tricks Calculation example in transient based on TLE42754G. The following load current profile is applied. IQ IQ1 IQ2 IQ,steady t1 Application conditions: VIN = 13.5V VOUT = 5V Ta = 85°C PCB: JEDEC 2s2p t2 t Load current: IQ1 = 400mA IQ2 = 250mA IQ,steady = 100mA t1 = 10ms t2 = 10s 25 20 15 10 5 0 10-5 10-4 10-3 10-2 10-1 100 101 102 103 104 t [s] Thermal impedance curve of TLE42754 in PG-TO263 package Determination of junction temperature Tj: P1 = (VI – VQ) × IQ1 + VI × Iq1 = (13.5V – 5V) × 400mA + 13.5V × 25mA = 3.74W Tj,t1 = Ta + P1 × RthJA,10ms = 85°C + 3.5K/W × 3.74W = 85°C + 13.1°C = 98.1°C < 150°C P2 = (VI – VQ) × IQ2 + VI × Iq2 = (13.5V – 5V) × 250mA + 13.5V × 10mA = 2.26W Tj,t2 = Ta + P2 × RthJA,10s = 85°C + 10.5K/W × 2.26W = 108.7°C < 150°C Psteady = (VI – VQ) × IQ,steady + VI × Iq,steady = (13.5V – 5V) × 100mA + 13.5V × 1.5mA = 0.87W Tj,steady = Ta + Psteady × RthJA = 85°C + 22K/W × 0.87W = 104.1°C < 150°C The calculation result shows that the junction temperature of TLE42754G never exceeds the maximum threshold of 150°C. This is a valid thermal design. 22 Application Details Choice of output capacitance An output capacitor is mandatory for the stability of linear voltage regulators. A linear voltage regulator can be described as a simple control system and the output capacitor is a part of the control system. Like all control systems, the linear voltage regulator has regions of instability. These regions depend to a great extent on two parameters of the system: the capacitance value of the output capacitor and its equivalent serial resistance ESR. VSupply I Q VDD Linear voltage regulator CQ There are some older linear voltage regulators (see the list below) which require a small amount of ESR at the output capacitor for stability. Those regulators were designed some time ago when tantalum capacitors were widely used. So, it is recommended to connect an additional series resistor to the capacitor if a ceramic capacitor is used. Load ESR 10 9 GND 8 ESR [Ω] GND Most Infineon linear voltage regulators are designed to be stable with extremely low ESR capacitors. According to the automotive requirements, ceramic capacitors with X5R or X7R dielectrics are recommended. Application diagram 7 6 5 4 The requirement for the output capacitor is specified in the datasheet of each linear voltage regulator. Stable region 3 2 Example: TLE42754 output capacitor requirements Parameter Symbol Output capacitor‘s requirements for stability Limit values Unit Conditions – µF The minimum output capacitance requirement is applicable for a worst case capacitance tolerance of 30% 3 Ω Relevant ESR value at f = 10kHz Min. Max. CQ 22 ESR (CQ) – 1 0 0.2 Typically an ESR versus output current plot can be found in the datasheet of Infineon voltage regulators showing the stability region. 100 101 IQ [mA] 102 500 Stability graph with minimum ESR requirement (TLE4271-2) Devices requiring small amount of ESR at CQ TLE42344 TLE42364 TLE4263/-2 TLE4268 TLE4270-2 TLE4271-2 TLE4278 TLE4285 TLE4290 TLE4294 TLE4295 TLE4296 TLE4471 TLF4476 103 ESR (CQ) [Ω] 10 It is very important to comply with the requirements of the output capacitor as specified in the datasheet during selection. If the specified requirements are not fulfilled, the voltage regulator can be unstable and the output voltage can oscillate. CQ = 22µF Tj = -40 … 150°C VI = 6 … 28V 2 Unstable region 101 100 Stable region 10-1 10-2 0 100 200 300 400 500 IQ [mA] Stability graph without minimum ESR requirement (TLE42754) 23 Application Details Tek Stopped 1794 Acqs 26 Jun 13 10:19:36 Design of input protection 4 Reverse polarity diode (recommended) 1 Input capacitor (recommended) I Line Battery 2 < 40V 10µF… 470µF 100nF… 470nF VQ Q Linear voltage regulator GND VDD CQ Load GND 2 Input buffer 3 Overvoltage suppressor (recommended) diode (optional) Ch2 100mV M 400µs 500KS/s 2.0µs/pt A Ch1 / 1.0V Stable output with CQ and ESR (CQ) according to the datasheet Tek Stopped 65 Acqs 26 Jun 13 10:22:15 Design of input protections The figure above shows the typical input circuitry for a linear voltage regulator. Though input filtering is not mandatory for the stability of a linear regulator, some external devices and filtering circuits are recommended in order to protect the linear voltage regulator against external disturbances and damage. 1 A ceramic capacitor at the input in the range of 100nF to 470nF is recommended to filter out the high frequency disturbances imposed by the line, e.g. ISO pulses 3a/b. This capacitor must be placed very close to the input pin of the linear voltage regulator on the PCB. 2 VQ An aluminum electrolytic capacitor in the range of 10µF to 470µF is recommended as an input buffer to smooth out high energy pulses, such as ISO pulse 2a. This capacitor should be placed close to the input pin of the linear voltage regulator on the PCB. 2 Ch2 100mV M 4.0µs 50.0MS/s 20.0ns/pt A Ch1 / 1.0V Oscillation with too high ESR (CQ) Tek Stopped 60 Acqs 26 Jun 13 10:13:08 An overvoltage suppressor diode can be used to further suppress any high voltage beyond the maximum rating of the linear voltage regulator and protect the device against any damage due to overvoltage. 3 For linear voltage regulators with an NPN bipolar or a MOSFET power stage, a reverse polarity diode is mandatory to protect the device from damage due to reverse polarity. Though the regulators with a PNP power stage have internal reverse polarity protection, a reverse polarity diode is still recommended in order to avoid damage due to excessively high reverse voltage, e.g. the ISO pulse 1. The reverse polarity diode can be put anywhere on the module between the battery and the input pin of the regulator. It can also be shared with other elements on the module. 4 2 VQ Old voltage regulator only Ch2 100mV Oscillation with too low ESR (CQ) 24 M 400µs 500KS/s 2.0µs/pt A Ch1 / 1.0V Application Details Drop-out voltage and tracking area Drop-out voltage Drop-out voltage is the minimum voltage differential between the input and output required for regulation. Regarding Infineon’s datasheet definition, it is determined when output voltage has dropped 0.1V from its nominal value. 500 IQ = 400mA 450 The graph below illustrates the tracking and regulating area of a linear regulator while the input voltage rises slowly during the start-up. Vdr [mV] 400 350 Tracking area When the input voltage is below the required minimum voltage, the linear regulator is not able to regulate the output voltage at its nominal value. However, as long as the input voltage is beyond a switching voltage threshold to turn the device off, the linear regulator is trying to maintain the output voltage. The output voltage is equal to VI – Vdr. This input voltage range is known as the tracking area, since the output voltage is following the input. IQ = 300mA 300 250 VI 200 IQ = 100mA 150 Tracking area: VQ follows VI 100 IQ = 10mA 50 0 -40 0 40 80 Vdr = (VI - VQ) @ (VQ,nom - 0.1V) Regulation area: VQ stabilized to VQ,nom 120 160 Tj [°C] VQ,nom Drop out voltage: Vdr = VI - VQ within tracking area, measured @ VQ,nom - 0.1V Typical drop-out voltage graphs (TLE42754) Minimum input voltage To regulate the output voltage at its nominal value, linear regulators require a minimum input voltage which is the nominal output voltage plus the maximum drop-out voltage (VQ,nom + Vdr,max). For example, consider a 5V regulator with a drop-out voltage of max. 0.5V. The minimum input voltage required for the 5V output is 5.5V. In the datasheet this value is specified as the minimum value for the input voltage and can be found under functional range. Example: TLE42754 input voltage range Parameter Input voltage Symbol VI Limit values Min. Max. 5.5 42 Unit V t Tracking Regulating Tracking area and drop-out voltage Extended input voltage range The newest Infineon linear voltage regulators start tracking at as low as 3.3V, which meets the requirement of cold cranking for automotive applications. The whole input voltage range, including the tracking area and the regulation area, is now specified as “Extended Input Voltage Range” in the datasheet. Example: TLF80511 input voltage range Conditions – Parameter Symbol Limit values Min. Max. Unit Conditions Input voltage range for normal operation VI VQ, nom + Vdr 40 V – Extended input voltage range VI,ext 3.3 40 V 1) 1) Between min. value and VQ.nom + Vdr : VQ = VI − Vdr. Below min. value: VQ = 0V 25 Application Details Load transients Every linear voltage regulator has an integrated control loop regulating output voltage. Different concepts of control loop can be implemented depending on the application. However, every regulation loop has a certain reaction time to adapt to load current variations. In a short period of time, the control loop is not able to react. It takes a minimum time for the voltage regulator to react and to set the output voltage back to its nominal value by adjusting the output current. In other words, voltage variations at the regulator’s output are inevitable for a short time during current transient. Typical application case: supply for a microcontroller The current consumption of a microcontroller is usually less than 1mA in standby mode and from several 10mA up to a few 100mA in normal operating mode. In its application, the microcontroller is triggered from standby mode to normal operating mode or vice versa. A fast current transient is respectively rising or falling in 1µs at the voltage regulator’s output. The typical behavior of a linear voltage regulator at these current transients is shown in the figures below. IQ Potential risks of big voltage variations are: Triggering an unwanted reset. Malfunction of the supplied microcontroller by exceeding its operating range. Damage of load by exceeding its maximum ratings. To avoid big output voltage variations, basically two solutions are possible: Avoid big load current transients whenever possible. The designer should first of all try to avoid big current transients within the application. Increase the value of the output capacitor to buffer the voltage regulator’s output voltage. In case big load current transients are not avoidable, increasing the output capacitance can lower the voltage variations at load current transients and avoid the risks. The following pictures show the output voltage deviation of the TLE42754 at a load current transient from 1mA to 200mA with 22µF and 100µF output capacitors. Whereas a voltage drop of 180mV has been recorded with a 22µF output capacitor, the drop is reduced to only 85mV with a 100µF output capacitor. Tek Run Hi Res 19 Jun 13 15:44:34 70mA CQ = 22µF 2 1mA VQ t [µs] Max. voltage ∆V 5V 200mA t [µs] Reaction time IQ 3 70mA IQ 1mA Ch3 200mV 1mA Ch2 100mV M 40.0µs 125MS/s 8.0ns/pt A Ch3 / 104mV t [µs] VQ 5V TLE42754 output voltage deviation at load transient with a 22µF output capacitor ∆V Min. voltage Reaction time Output voltage deviation at load transient 26 ∆VQ = 180mV VQ t [µs] Application Details Tek Run Hi Res 19 Jun 13 16:01:13 CQ = 100µF 2 The overshoot level during the start-up is dependent on the load current and the output capacitor. The effect of the output capacitor on the voltage overshoot is shown in the following graphs: VQ ∆VQ = 85mV Tek Run Hi Res 21 Jun 13 13:57:03 14V 200mA 3 IQ VQ,peak = 5.47V 1mA 3 Ch3 200mV Ch2 100mV VI 0V M 40.0µs 125MS/s 8.0ns/pt A Ch3 / 104mV TLE42754 output voltage deviation at load transient with a 100µF output capacitor 2 VQ CQ = 22µF To dimension the output capacitor reasonably, the following steps are recommended: Check for worst-case current transients within the application. Define max. allowed voltage variation ΔVmax during current transient. Determine the voltage variation ΔV of the voltage regulator at the worst-case current transient with the minimum output capacitance fulfilling the requirement for stability. If ΔV is higher than ΔVmax, try with a bigger output capacitance. Choose an output capacitor which ensures the voltage variation ΔV is within the allowed range. Verify the selected output capacitor on the application hardware. Ch3 5.0V Ch2 1.0V M 200µs 25.0MS/s 40.0ns/pt A Ch3 / 2.8V TLF42754 output voltage deviation at load transient with a 22µF output capacitor Tek Stopped 1 Acqs 21 Jun 13 13:48:04 14V VQ,peak = 5.25V 3 2 VI 0V VQ CQ = 100µF Overshoot at start-up During the start-up, i.e. while the input voltage is powered on, the linear voltage regulator is driving the maximum output current to charge the output capacitor and raise the output voltage to the nominal value. When the nominal output voltage is reached, the control loop of the linear voltage regulator needs a few microseconds to react. During these few microseconds, the regulator is still charging the output cap, leading to a further increase of the output voltage. After those few microseconds, the regulator starts regulating the output voltage to the nominal voltage. Ch3 5.0V Ch2 1.0V M 200µs 25.0MS/s 40.0ns/pt A Ch3 / 2.8V TLF42754 output voltage deviation at load transient with a 100µF output capacitor To smooth out voltage overshoot on start-up, two measures are recommended: Increase the capacitor value at the input to slow down the slope of the input voltage. Increase the output capacitor value to slow down the slope of the output voltage. 27 Application Details PCB layout Below is an example of a good PCB layout design: The PCB layout design is important for the performance of a linear voltage regulator. A good PCB layout can optimize the performance, whereas a poor one may impact on the stable operation of the regulator and introduce various disturbances in the system. Here are some general recommendations for the PCB design with a linear voltage regulator: Place the output capacitor as close as possible to the regulator’s output and GND pins and on the same side of the PCB as the regulator. Place the ceramic input capacitor (e.g. 100nF) as close as possible to the regulator’s input pin and on the same side of the PCB as the regulator. Place the larger input buffer capacitor (e.g. 10µF) on the same PCB. Traces connected to the regulator’s input and output should be sized according to the current flowing through it. Ensure a good GND connection. For 4 or more layer PCBs, use one middle layer for GND and place sufficient number of vias to GND layer. For a 1 or 2 layer PCB, place a sufficient GND plane. The PCB layout design is also crucial to the thermal performance. Here are some recommendations for a good thermal design: Ensure good thermal connection. Place sufficient cooling area depending on the power dissipation. For 4 or more layer PCBs, place sufficient number of thermal vias to the thermal layer. Put other heat sources on the board as far away as possible from the position of the linear voltage regulator. 28 GND plane GND vias Output capacitor Input capacitor 3 1 4 Input pin Output pin 3 3 2 1 2 4 LDO Thermal vias 5 6 PCB layout example Application Schematic Application Schematic VBAT Linear voltage regulator I e.g. Ignition EN Q Regulated output voltage R1 RRA1 RRO RWO RSO VA Internal supply CQ Load (e. g. Microcontroller) RO RSI1 Protection circuits CI Bandgap reference Reset and watchdog generator WO WI RADJ SO SI GND RSI2 D R2 CD GND RRA2 General application schematic for bipolar voltage regulators with analog reset and watchdog timing control Linear voltage regulator VBAT Q I e.g. Ignition EN Regulated output voltage R1 Internal supply CQ Protection circuits RSO Bandgap reference Reset and watchdog generator WO WI WM1/2 SO SI RSI2 RWO Load (e. g. Microcontroller) RO RSI1 CI RRO VA GND R2 GND General application schematic for MOSFET voltage regulators with digital reset and watchdog timing control 29 Packages Packages 30 PG-DSO-8 PG-DSO-8 (Exposed Pad) PG-DSO-14 PG-DSO-20 PG-DSO-20 (Power-SO) SCT595 SOT223 PG-SSOP-14EP PG-TO252-3 (DPAK) PG-TO252-5 (DPAK-5-leg) PG-TO263-3 (TO220-3 (SMD)) PG-TO263-5 (TO220-5 (SMD)) PG-TO263-7 (TO220-7 (SMD)) TSON-10 Glossary Glossary ADJ CD CI CQ D EN ESR I ID,wd,max INH Iq IQ,MAX Iq,steady Adjustable output Delay capacitor Input capacitor Output capacitor Delay capacitor pin for reset and watchdog Enable pin Equivalent series resistance Input pin Maximum watchdog discharge current Inhibit pin (ref. EN) Quiescent current Maximum output current Steady state quiescent current PD Power dissipation Psteady Steady state power Q Output pin QADJ Adjustable output pin R1 Output voltage adjust resistor 1 R2 Output voltage adjust resistor 2 RADJ Reset threshold adjust pin RADJ,1 Reset threshold adjust resistor 1 RADJ,2 Reset threshold adjust resistor 2 RO Reset output pin RPU,D Pull-up resistor at D pin for watchdog Deactivation RRO Reset output internal pull-up resistor RRO,ext Reset output external pull-up resistor RSI1 Sense input voltage divider resistor 1 RSI2 Sense input voltage divider resistor 2 RthJA Junction to ambient thermal resistance RthJC Junction case thermal resistance RWO,ext Watchdog output external pull-up resistor SI Sense input pin SO Sense output pin Ta Ambient temperature Tj Junction temperature Tj,max Maximum junction temperature Tj,sd Thermal shutdown junction temperature Tj,shd Thermal shutdown junction temperature Hysteresis Tj,steady Steady state junction temperature trd Power-on reset delay time trd,100nF Power-on reset delay time with 100nF Capacitor trr Reset reaction time trr,d,100nF Reset reaction time delay with 100nF Capacitor trr,int Internal reset reaction time tSTARTUP Start-up time tWD,low VA VBAT VD VDD VDL VDU VI VI,TH VQ VQ,nom Vref VRO VRT VSI VWI VWO WI WM1 WM2 WO ZthJA Low watchdog time Voltage adjust pin Battery voltage Voltage at D pin Supply pin of microcontroller Delay capacitor lower threshold Delay capacitor upper threshold Input voltage Threshold trigger the early warning Output voltage Nominal output voltage Internal reference voltage Reset output voltage Reset threshold Sense input voltage Watchdog input voltage Watchdog output voltage Watchdog input pin Watchdog mode Selection Pin 1 Watchdog mode Selection Pin 2 Watchdog output Junction ambient thermal impedance 31 Ask Infineon. 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