B5973DTR

B5973D 2 A step down switching regulator for automotive applications Datasheet - production data  Protection against feedback disconnection  Thermal shutdown Applications HSOP8 - exposed pad  Dedicated to automotive applications Description Features The B5973D is a step down monolithic power switching regulator with a minimum switch current limit of 2.25 A so it is able to deliver up to 2 A DC current to the load depending on the application conditions. The output voltage can be set from 1.235 V to 35 V. The high current level is also achieved thanks to an HSOP8 package (i.e. SO8 package with exposed frame), that allows to reduce the Rth(JA) down to approximately 40 °C/W. The device uses an internal P-channel DMOS transistor (with a typical RDSon of 250 m) as switching element to minimize the size of the external components. An internal oscillator fixes the switching frequency at 250 kHz. Having a minimum input voltage of 4 V only, it is particularly suitable for 5 V bus. Pulse by pulse current limit with the internal frequency modulation offers an effective constant current short-circuit protection.  Qualified following the AEC-Q100 requirements (temperature Grade 1), see PPAP for more details.  2 A DC output current  Operating input voltage from 4 V to 36 V  3.3 V / (± 2 %) reference voltage  Output voltage adjustable from 1.235 V to 35 V  Low dropout operation: 100 % duty cycle  250 kHz internally fixed frequency  Voltage feedforward  Zero load current operation  Internal current limiting  Inhibit for zero current consumption  Synchronization Figure 1. Typical application 95() 9,1 9 WR 9 9&& 6 2.2 V 50 100 A VCC = 36 V; Vinh > 2.2 V 80 150 A 0.8 V Inhibit INH threshold voltage Device ON Device OFF 2.2 V 3.5 V Error amplifier VOH High level output voltage VFB = 1 V VOL Low level output voltage VFB = 1.5 V Io source Source output current Io sink Sink output current Ib Source bias current DC open loop gain 6/44 VCOMP = 1.9 V; VFB = 1 V VCOMP = 1.9 V; VFB = 1.5 V 0.4 190 300 A 1 1.5 mA 2.5 RL =  DocID14117 Rev 4 V 50 65 4 A dB B5973D Electrical characteristics Table 4. Electrical characteristics (TJ = -40 °C to 125 °C, VCC = 12 V, unless otherwise specified) (continued) Symbol gm Parameter Transconductance Test condition Min. ICOMP = -0.1 mA to 0.1 mA; VCOMP = 1.9 V Typ. Max. 2.3 Unit mS Synch function High input voltage VCC = 4.4 to 36 V Low input voltage VCC = 4.4 to 36 V Slave synch current Vsynch = 0.74 V (2) Vsynch = 2.33 V 2.5 0.11 0.21 VREF V 0.74 V 0.25 0.45 mA Master output amplitude Isource = 3 mA 2.75 3 V Output pulse width no load, Vsynch = 1.65 V 0.20 0.35 s 3.2 3.3 3.399 V 5 10 mV 8 15 mV 18 35 mA Reference section Reference voltage Line regulation Load regulation IREF = 0 to 5 mA VCC = 4.4 V to 36 V IREF = 0 mA VCC = 4.4 V to 36 V IREF = 0 mA Short-circuit current 5 1. With TJ = 85 °C, Ilim_min = 2.5 A, assured by design, characterization and statistical correlation. 2. Guarantee by design. DocID14117 Rev 4 7/44 44 Datasheet parameters over the temperature range 4 B5973D Datasheet parameters over the temperature range The 100% of the population in the production flow is tested at three different ambient temperatures (-40 C; +25 C, +125 C) to guarantee the datasheet parameters inside the junction temperature range (-40 C; +125 C). The device operation is so guaranteed when the junction temperature is inside the (-40 C; +150 C) temperature range. The designer can estimate the silicon temperature increase respect to the ambient temperature evaluating the internal power losses generated during the device operation (please refer to Section 2.2: Thermal data on page 5). However the embedded thermal protection disables the switching activity to protect the device in case the junction temperature reaches the TSHTDWN (+150 C ± 10 C) temperature. All the datasheet parameters can be guaranteed to a maximum junction temperature of +125 C to avoid triggering the thermal shutdown protection during the testing phase because of self heating. 8/44 DocID14117 Rev 4 B5973D 5 Functional description Functional description The main internal blocks are shown in the device block diagram in Figure 3. They are:  A voltage regulator supplying the internal circuitry. From this regulator, a 3.3 V reference voltage is externally available.  A voltage monitor circuit which checks the input and the internal voltages.  A fully integrated sawtooth oscillator with a frequency of 250 kHz 15 %, including also the voltage feed forward function and an input/output synchronization pin.  Two embedded current limitation circuits which control the current that flows through the power switch. The pulse-by-pulse current limit forces the power switch OFF cycle by cycle if the current reaches an internal threshold, while the frequency shifter reduces the switching frequency in order to significantly reduce the duty cycle.  A transconductance error amplifier.  A pulse width modulator (PWM) comparator and the relative logic circuitry necessary to drive the internal power.  A high side driver for the internal P-MOS switch.  An inhibit block for standby operation.  A circuit to implement the thermal protection function. Figure 3. Block diagram 9&& 92/7$*(6 021,725 75,00,1* 6833/< ,1+ 7+(50$/ 6+87'2:1 ,1+,%,7 9 95() %8))(5 95() 3($.723($. &855(17/,0,7 &203 ($ )%   9 3:0  ' 6(7 4  '5,9(5 &/5 4 6 IL TOFF so the current escalates and the balance between Equation 30 and Equation 31 occurs at a current slightly higher than the current limit. This must be taken into account in particular to avoid the risk of an abrupt inductor saturation. DocID14117 Rev 4 29/44 44 Application information B5973D Figure 15. Short-circuit current VIN = 12 V Figure 16. Short-circuit current VIN = 24 V 30/44 DocID14117 Rev 4 B5973D Application information Figure 17. Short-circuit current VIN = 36 V 8.5 Application circuit Figure 18 shows the evaluation board application circuit, where the input supply voltage, VCC, can range from 4 V to 36 V and the output voltage is adjustable from 1.235 V to 6.3 V due to the voltage rating of the output capacitor,. Figure 18. Evaluation board application circuit / —+ 95() 9,1  9  WR 9 9&& 6