BM2490

BM2490 BOOKLY | Alldatasheet

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Technical content

1 www.bookly.com BM2490 2 . 5 A C C o r C V B U C K 催ᬜ⥛ 2.5Aᘦ⌕ᘦय़䰡य़䕀ᤶ఼ TYPICAL APPLICATION

DESCRIPTION

The BM2490 is a monolithic step-down switch mode converter with a programmable output current limit. It achieves 2.5A continuous output current over a wide input supply range with excellent load and line regulation. The maximum output current can be programmed by sensing current through an accurate sense resist or. It can out put const ant current and volt age. Int ernal thermal shut down, cycle-by-cycle current limit prot ection. The BM2490 requires a minimum number of readily available st andard external component s. The BM2490 is available in 8-pin SOIC8-EP packages . MP2490୔ඹԅSOP8ᅭᄚပ1.5A BM2490ēESOP8ᅭēટᆳӾ2.5A,3A-max, pin-pin MP2490 ԅဈဟкѩēUSBԨၗēLED௚Վd ಁՇԅԨঠ ঠ೛ѻಁՇԅԨঠd带精准的后端限流.

FEATURES

/g144Wide 4.3V to 37V Operating I nput Range /g1442.5A continusly, up to 3A-max out put Current /g144Output Adjust able f rom 0.8V to 15V /g144Programmable Out put Current Limit wit hout power loss /g1440. 25Ω Internal Power MOSFET Switch /g144Stable with Low ESR Output Ceramic Capacitors /g14494% Efficiency @ 500mA (Vo=5V) /g144Fixed 900KHz Frequency /g144Thermal Shutdown /g144Cycle-by-Cycle Over Current Prot ect ion /g144Available in 8-Pin SOIC8-EP Packages APPLICAT IONS /g144USB Power Supplies /g144Automotive Cigarette Lighter Adapters /g144Power Supply for Linear Chargers 0.1 1 10 100 VOUT=5V EFFICIENCY (%) LOAD CURRENT (A) VIN=8V VIN=12V VIN=24V 㛑,Ԣ䴭ᗕ⬉⌕ Iq=380uA, य़Ꮒ 1V@5V-0.5A IC䚼Ꮖ㒣᳝䰤⌕,ࠄ3A䰤⌕, R3ᇣ PWMކ,᳈ད䖛 EMC,гৃҹⷁ䏃ᥝ. Rs=40mohm 如果空负载输出电压不稳,在输出端对地加个1-3K电阻负载即可.R1 ϸッᑊϾ 10nFᕫᇣ.

2 www.bookly.com BM2490

ORDERING INFORMATION

PIN No. PIN NAME PIN DESCRIPTION 1V I N Supply Voltage. The BM2490 operates from a +4. 5V to +36V unregulated input. CIN is needed to prevent large voltage spikes from appearing at the input. Put CIN as close to the IC as possible. It is the drain of the internal power device and power supply for the whole chip. 2G n d Ground. This pin is the voltage reference for t he regulated out put voltage. For this reason care must be taken in it s layout. This node should be placed out side of the D1 to C IN ground pat h to prevent switching current spikes from inducing voltage noise int o the part. 3F B Feedback. An external resist or divider from the out put to G ND, tapped to the FB pin set s the output voltage. To prevent current limit run away during a short circuit fault condition the frequency-fold-back comparator lowers t he oscillat or frequency when the FB volt age is below 250mV. 4 SS Connect to an external capacitor used for Soft-Start and compensation for current limit ing loop. 5 ISN Negative Current Sense I nput for load current limit ing. 6 ISP Posit ive Current Sense Input for load current limiting. 7B S Bootstrap. This pin act s as the positive rail for the high -side switch’s gate driver. Connect a 10nF between this pin and SW . 8S W Switch Output. Connect this pin to the switching end of the inductor. 9 Exposed pad. Connected it to Gnd ABSOLUTE MAXIMUM RATINGS (1) Recommended Operating Conditions(2) Output Voltage VOUT (VIN>16.5V) 0.8V to 15V Thermal Resistance (3) θ JA θ JC Notes : 1) Exceeding these ratings may damage the device. 2) The device is not guaranteed to function outside of its operating conditions. 3) Measured on approximately 1” square of 1 oz copper. PART NUMBER BM2490 TEMPERA TURE RANGE -40/g113C to 85/g113C PACKAGE SOIC8-EP VIN GND FB SS ISN ISP BS SW BM2490

3 www.bookly.com BM2490

ELECTRICAL CHARACTERISTICS

VIN = 12V, TA = +25°C, unless otherwise noted. PARAM ET ER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT Feedback Voltage VFB 4.5V ≤ VIN ≤ 36V 0.785 0.805 0.825 V Feedback Bias Current IBIAS(FB) VFB = 0.8V 10 nA Switch On Resistance RDS(ON) 0.25 Ω Switch Leakage VEN = 0V, VSW = 0V 0.1 10 μA Current Limit (4) 2.5 2.8 3.1 A Oscillator Frequency fSW VFB = 0.6V 700 900 1000 KHz Fold-Back Frequency VFB = 0V 200 KHz Boot-Strap Voltage VBST -V SW 6 V Minimum On Time (4) tON VFB = 1V 100 ns Under Voltage Lock out Threshold Rising 3.0 3.3 3.6 V Under Voltage Lock out Threshold Hysteresis 200 mV Supply Current (Quiescent) VEN = 2V, VFB = 1V 400 700 μA Thermal Shut down(4) 160 °C Current Sense Voltage VISP -VISNVISP, VISN 0.4-15V 85 95 105 mV Input Bias Current (ISN, ISP) IBIAS (ISN,I SP)VISP, VISN 0.4-15V -1 0.1 +1 uA Note : 4) Guaranteed by design Figure 2 . Functional Block Diagram

4 www.bookly.com BM2490 TYPICAL PERFORMANCE CHARACTERISTICS C1=C2=4.7μF, C4=0.22μF, C5=C6=10μF, L=10μH, TA=25ºC, unless otherwise noted 0.1 1 10 100 VOUT=5V EFFICIENCY (%) LOAD CURRENT (A) VIN=8V VIN=12V VIN=24V 0.1 1 10 100 VOUT=3.3V EFFICIENCY (%) LOAD CURRENT (A) VIN=8V VIN=12V VIN=24V 0.1 1 10 100 VOUT=12V EFFICIENCY (%) LOAD CURRENT (A) VIN=18V VIN=24V

5 www.bookly.com BM2490 TYPICAL PERFORMANCE CHARACTERISTICS(continued) C1=C2=4.7μF, C4=0.22μF, C5=C6=10μF, L=10μH, TA=25ºC, unless otherwise noted L o a d R e g u l a t o r S S V o l t . – S o f t s t a r t C a p . C V - C C c u r v e 4.90 4.95 5.00 5.05 5.10 5.15 5.20 VOUT=5V VOUT (V) LOAD CURRENT (A) VIN=8V VIN=12V VIN=24V 0.0 0.2 0.4 0.6 0.8 1.0 ILOAD=2A SS (V) SS SOFT-START TIME (s) 0.1nF 0.22nF 0.33nF 5VOUT (V) ILOAD (A) VOUT OPERA TION Main Control Loop The BM2490 is a current mode buck regulator. That is, the error amplifier (EA) output voltage is proportional to the peak inductor current. At the beginning of a cycle, the integrated high side power switch M1 is off; the EA output voltage is higher than the current sense amplifier output; and the current comparator’s output is low. The rising edge of the 900KHz clock signal sets the RS Flip -Flop. Its output turns on M 1 thu s connecting the SW pin and inductor to the input supply. The increasing inductor current is sensed and amplified by the Current Sense Amplifier. Ramp compensation is added to Current Sense Amplifier output and compared to the Error Amplifier output by the PWM Comparator. When the Current Sense Amplifier plus Slope Compensation signal exceeds the EA output voltage, the RS Fl ip-Flop is reset and the BM2490 reverts to its initial M 1 off state. If the Current Sense Amplifier plus Slope Compensation signal does not exceed the COM P voltage, then the falling edge of the CLK resets the Flip-Flop. The output of the Error Amplifier integrates the voltage difference between the feedback and the 0.8V bandgap reference. The polarity is such that a FB pin voltage lower than 0.8V increases the EA output voltage. Since the EA output voltage is proportional to the peak inductor current, an increase in its voltage increases current delivered to the output. An external Schottky Diode (D1) carries the inductor current when M1 is off. Load Current Limiting Loop The output current information is sensed via the ISP and ISN p ins. The regulation threshold is set at 95 mV . If VSENSE, the difference of VISP and VISN, is less than 95mV , the output voltage of the power supply will be set by the FB pin. If VSENSE reaches 95mV , the current limit loop will pull down SS and regulate the output at a constant current determined by the external sense resistor. The external capacitor on SS pin is the dominant compensation capacitor for load current regulation loop. The capacitor has normal value of 220nF, which will put the bandwidth of load current regulation loop to be less than 1 kHz. When VSENSE is higher than 95mV , SS will not drop down to the final regulation level immediately. It will cause the load current to be higher than the programmed level for a short period. A fast comparator is added to shut down power switch when the average load current is higher than 120% of the programmed current limit level. An accurate sense resistor can be used for load current sensing.

6 www.bookly.com BM2490 APPLICATION INFORMA TION Setting the Output V oltage The external resistor divider is used to set the output voltage (see the schematic on front page). The feedback resistor R1 also sets the feedback loop bandwidth with the internal compensation capacitor (see Figure 1). Choose R1 to be around 300kΩ for optimal transient response. R2 is then given by: 12 / 0.8 1OUT RR V/g32 /;#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323 Tabl e 1 –Resistor Selection for Common V out(V) R1(K Ω) R2(KΩ) 3.3 300(1%) 96(1%) 5 300(1%) 57.1(1%) Selecting the Inductor A 1μH to 15μH inductor with a DC current rating of at least 25% percent higher than the maximum load current is recommended for most applications. For highest efficiency, the inductor DC resistance should be less than 200 mΩ. For most designs, the inductance value can be derived from the following equation. sw OUT IN OUT IN L VV VL VI /g117/;#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323/g32 /g117/g39 /g117/g103 Where ΔIL is the inductor ripple current. Choose inductor current ripple to be approximately 30% of the maximum load current,. The maximum inductor peak current is: () () L LM A X LM A X III /;#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323 /g39/g32 Under light load conditions below 100mA, larger inductance is recommended for improved efficiency. Output Current Sensing The output current can be sensed through the accurate sense resistor, as in Figure 3, where the output current limit is set as: S mV R LM A XI /;#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323/;#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323#2323/g32 ISP ISN SW Cout Rs Vout Figure 3: Current Sensing Methods Selecting the Input Capacitor The input capacitor reduces the surge current drawn from the input and also the switching noise from the device. The input capacitor impedance at the switching frequency should be less than the input source impedance to prevent high frequency switching current from pass to the input. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. For most applications, a 4.7μF capacitor is sufficient. Selecting the Output Capacitor The output capacitor keeps output voltage small and ensures regulation loop stability. The output capacitor impedance should be low at the switching frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended. PC Board Layout 1) The high current paths (GND, V IN and SW) should be placed very close to the device with short, direct and wide traces. 2) The input capacitor needs to be as close as possible to the VIN and GND pins. 3) The external feedback resistors should be pl aced next to the FB pin. Keep the switching node SW short and away from the feedback network. 4) ISN, ISP are sensitive nodes. Put the sensing components as close to the device as possible and keep them away from the high current and noisy paths such as GND, V IN, SW). M atch the trace and components on ISN, ISP paths as good as possible.

7 www.bookly.com BM2490 PCB reference: BOM LIST FOR 5V/2.2A Car Charger: Ref Value Descripti on Package M a nufact urer Qt y M a nufacturer P/N C1, C2 4.7uF Ceramic Ca p., 50V, X7R 1210 muRa ta 2 GRM 32ER71H475K C3 10nF Ceramic Ca p., 50V, X7R 0603 muRa ta 1 GRM 188 R71H103 K C4 0.22uF Ceramic Ca p., 16V, X7R 0603 muRa ta 1 GRM 188 R71C224 K C5, C6 10uF Ceramic Ca p., 25V, X7R 1210 muRa ta 2 GRM 32 DR71E106K D1 3A Schot tk y Di ode, S MD, 40V, 3A SM A ON Semico nd uct or

1 M BRA340 T3 GOSCT

L1 10uH DS85LC I nductor, 2.3A/51 mΩ SM D TOK O 1 B1000AS-100 M R1 300KΩ Film Re s., 1% , 300KΩ 0603 Panasonic 1 ERJ-3EKF3003V R2 57.1KΩ Film Re s., 1% , 57.1KΩ 0603 Panasonic 1 ERJ-3EKF5712V RS 40mΩ Film Re s., 1% , 40mΩ 2010 Vishay 1 WSLF040 TR- ND U1 DC-D C Conv erter SOP8-EP BM 2 490 1 90%ⱘ催ᬜ⥛, ⣀⡍ⱘ LEDߎ,໪䚼ᇣ⬉ᛳ6.8-22UH

8 www.bookly.com BM2490 PACKAGE OUTLINE SOIC8-EP PACKAGE OUTLINE AND DIMENSIONS