70301032

BM1588 BOOKLY | Alldatasheet

Document overview

• Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
• PDF pages: 6

Technical content

Features

• Wide 4V to 18V Operating Input Range
• 2A Continuous Output Current
• No Schottky Diode Required
• 500KHz Frequency Operation
• Built-in Over Current Limit
• Built-in Over V oltage Protection
• Internal Soft start
• Output Adjustable from 0.8V
• Integrated internal compensation
• Short Protection with Hiccup-Mode
• Thermal Shutdown
• Available in SOT23-6 Package
• -40°C to +85°C Temperature Range

Applications

• Digital Set-top Box (STB)
• Tablet Personal Computer (Pad)
• Flat-Panel Television and Monitor
• Wi-Fi Router / AP
• Digital Video Recorder (DVR)
• Portable Media Player (PMP)
• Cable Modem / XDSL
• General Purposes General Description The BM1588 is a high frequency, synchronous, rectified, step-down, switch-mode converter with internal power MOSFETs. It offers a very compact solution to achieve a 2A continuous output current over a wide input supply range, with excellent load and line regulation. The BM1588 requires a minimal number of readily available, external components and is available in a space saving SOT23-6 package. Typical Application Circuit COUTR1 CIN IN SW EN FB GND VIN VOUT BS ON/ OFF CFF COUTR1 BS ON/ OFF CFF

Figure 1. Basic Application Circuit

Vin, EN, V oltage …………………... -0.3V to 19V Operating Temperature Range ….. -40°C to +85°C Lead Temperature (Soldering, 10s) ……... +300°C Thermal Resistance (θJA) ……………..160 °C/W Thermal Resistance（θJC）………...…130 °C/W Storage Temperature Range …………… -65°C to 150°C BS V oltage …………………….. (Vsw-0.3) to (Vsw+5V) ESD (Human Body Made) HMB…………………2 KV Note 1: Exceeding these ratings may damage the device. Note 2: The device is not guaranteed to function outside of its operating conditions Pin Description Pin Configuration BS FB EN GND IN SW BS FB EN GND IN SW TOP VIEW SOT23-6 BS FB EN GND IN SW TOP VIEW SOT23-6 Pin Description Pin Name Function

1 GND GROUND Pin

2 SW Switching Pin

3 IN Power Supply Pin

4 FB Adjustable V ersion Feedback input. Connect FB to the center point of the external resistor divider 5 EN Drive this pin to a logic-high to enable the IC. Drive to a logic-low to disable the IC and enter micro-power shutdown mode. 6 BS Bootstrap. A capacitor connected between SW and BST pins is required to form a floating supply across the high-side switch driver. Order Information Marking Part No. Model Description Package MOQ BFYLL 70301032 BM1588 BM 1588 Buck, 4-18V , 2A, 500KHz, VFB 0.8V , SOT23-6 SOT23-6 3000PCS BM1588 BooklyMicro semiconductors www.bookly.com

Electrical Characteristics

Parameter Test Conditions Min Typ Max Unit Input V oltage Range 4 18 V Supply Current in Operation VEN=3.0V , VFB=1.1V 0.5 mA Supply Current in Shutdown VEN =0 or EN = GND 4 uA Regulated Feedback V oltage TA = 25°C, 4V≤VIN ≤18V 0.784 0.8 0.816 V High-Side Switch On-Resistance 120 m Ω Low-Side Switch On-Resistance 90 m Ω High-Side Switch Leakage Current VEN=0V , VSW=0V 0 10 uA Upper Switch Current Limit Minimum Duty Cycle 3 A Oscillation Frequency 0.5 MHz Maximum Duty Cycle VFB=0.8V 92 % Minimum On-Time 60 nS Minimum Off-Time 90 nS Soft Start 1.2 mS Thermal Shutdown 160 ℃ Thermal Hysteresis 20 ℃ Functional Block Diagram VCC REGULATOR OSCILLATOR REFERENCE 400k56pF 1pF COMPARATOR ON TIME CONTROL LOGIC CONTROL BOOST REGULATOR HS DRIVER LS DRIVER VCC VCC VIN EN FB GND SW BS CURRENT LIMIT COMPARATOR CURRENT SENSE AMPLIFIER RSEN ERROR AMPLIFIER Figure 2. BM 1588 Block Diagram

The BM1588 is a current mode step down DC/DC converter that provides excellent transient response with no extra external compensation components. This device contains an internal, low resistance, high voltage power MOSFET, and operates at a high 500K operating frequency to ensure a compact, high efficiency design with excellent AC and DC performance. Error Amplifier The error amplifier compares the FB pin voltage with the internal FB reference (VFB) and outputs a current proportional to the difference between the two. This output current is then used to charge or discharge the internal compensation network to form the COMP voltage, which is used to control the power MOSFET current. The optimized internal compensation network minimizes the external component counts and simplifies the control loop design. Internal Soft-Start The soft-start is implemented to prevent the converter output voltage from overshooting during startup. When the chip starts, the internal circuitry generates a soft-start voltage (SS) ramping up from 0V to 0.8V . When it is lower than the internal reference (REF), SS overrides REF so the error amplifier uses SS as the reference. When SS is higher than REF, REF regains control. The SS time is internally fixed to 1.2ms. Over Current Protection & Hiccup The BM1588 has cycle-by-cycle over current limit when the inductor current peak value exceeds the set current limit threshold. Meanwhile, output voltage starts to drop until FB is below the Under-V oltage (UV) threshold, typically 25% below the reference. Once a UV is triggered, the BM1588 enters hiccup mode to periodically restart the part. This protection mode is especially useful when the output is dead-short to ground. The average short circuit current is greatly reduced to alleviate the thermal issue and to protect the regulator. The BM1588 exits the hiccup mode once the over current condition is removed. Startup and Shutdown If both VIN and EN are higher than their appropriate thresholds, the chip starts. The reference block starts first, generating stable reference voltage and currents, and then the internal regulator is enabled. The regulator provides stable supply for the remaining circuitries. Three events can shut down the chip: EN low, VIN low and thermal shutdown. In the shutdown procedure, the signaling path is first blocked to avoid any fault triggering. The COMP voltage and the internal supply rail are then pulled down. The floating driver is not subject to this shutdown command. BM1588 BooklyMicro semiconductors www.bookly.com

Setting the Output Voltage BM1588 require an input capacitor, an output capacitor and an inductor. These components are critical to the performance of the device. BM1588 are internally compensated and do not require external components to achieve stable operation. The output voltage can be programmed by resistor divider. 𝑉𝑂𝑈𝑇 = 𝑉𝐹𝐸𝐸𝐷𝐵𝐴𝐶𝐾×𝑅1+𝑅2 OUTPUT R1(KΩ) R2 (KΩ) L1(MIN) L1(TYP) L1(MAX) CIN COUT 1.05V 150 480 2.2 uH 4.7 uH 4.7 uH 20-47uF 20-68uF 1.2V 150 300 2.2 uH 4.7 uH 4.7 uH 20-47uF 20-68uF 1.5V 160 180 3.3 uH 4.7 uH 4.7 uH 20-47uF 20-68uF 3.3V 160 51 3.3 uH 4.7 uH 6.8 uH 20-47uF 20-68uF 5.0V 160 30 3.3 uH 4.7 uH 6.8 uH 20-47uF 20-68uF Use a T-type network for when VOUT is low. Selecting the Inductor The recommended inductor values are shown in the Application Diagram. It is important to guarantee the inductor core does not saturate during any foreseeable operational situation. The inductor should be rated to handle the peak load current plus the ripple current: Care should be taken when reviewing the different saturation current ratings that are specified by different manufacturers. Saturation current ratings are typically specified at 25°C, so ratings at maximum ambient temperature of the application should be requested from the manufacturer. OSCLin outinout f I V V V VL      ) ( Where ΔIL is the inductor ripple current. Choose inductor ripple current to be approximately 30% if the maximum load current, 2A. The maximum inductor peak current is: ) ( L LOADMAX L II I   Under light load conditions below 100mA, larger inductance is recommended for improved efficiency. V out R1(KΩ) R2(KΩ) R3(KΩ) 5.0V 40.2 7.68 75 3.3V 40.2 13 75 2.5V 40.2 19.1 100 1.8V 40.2 32.4 120 1.2V 20.5 41.2 249 1.05V 32.4 300 BM1588 BooklyMicro semiconductors www.bookly.com

Selecting the Output Capacitor Special attention should be paid when selecting these components. The DC bias of these capacitors can result in a capacitance value that falls below the minimum value given in the recommended capacitor specifications table. The ceramic capacitor’s actual capacitance can vary with temperature. The capacitor type X7R, which operates over a temperature range of −55°C to +125°C, will only vary the capacitance to within ±15%. The capacitor type X5R has a similar tolerance over a reduced temperature range of −55°C to +85°C. Many large value ceramic capacitors, larger than 1uF are manufactured with Z5U or Y5V temperature characteristics. Their capacitance can drop by more than 50% as the temperature varies from 25°C to 85°C. Therefore X5R or X7R is recommended over Z5U and Y5V in applications where the ambient temperature will change significantly above or below 25°C. Tantalum capacitors are less desirable than ceramic for use as output capacitors because they are more expensive when comparing equivalent capacitance and voltage ratings in the 0.47uF to 44uF range. Another important consideration is that tantalum capacitors have higher ESR values than equivalent size ceramics. This means that while it may be possible to find a tantalum capacitor with an ESR value within the stable range, it would have to be larger in capacitance (which means bigger and more costly) than a ceramic capacitor with the same ESR value. It should also be noted that the ESR of a typical tantalum will increase about 2:1 as the temperature goes from 25°C down to −40°C, so some guard band must be allowed. PC Board Layout Consideration PCB layout is very important to achieve stable operation. It is highly recommended to duplicate EVB layout for optimum performance. If change is necessary, please follow these guidelines and take Figure 4 for reference. 1. Keep the path of switching current short and minimize the loop area formed by Input capacitor, high-side MOSFET and low-side MOSFET. 2. Bypass ceramic capacitors are suggested to be put close to the Vin Pin. 3. Ensure all feedback connections are short and direct. Place the feedback resistors and compensation components as close to the chip as possible. 4. VOUT, SW away from sensitive analog areas such as FB. 5. Connect IN, SW, and especially GND respectively to a large copper area to cool the chip to improve thermal performance and long-term reliability. BM1588 BooklyMicro semiconductors www.bookly.com