H9108

H9108 18V,2A Synchronous Step-Down Converter Features  High efficiency:up to 96%  Wide 3.3V to 18V Operating input Range  2A Continuous Output Current  Output Adjustable from 0.6V  No Schottky Diode Required  Integrated internal compensation  600KHz Frequency Operation  Short Protection with Hiccup-Mode  Built-in Over Current Limit  Thermal Shutdown  Built-in Over Voltage Protection  Available in SOT23-6 Package  Internal Soft start  -40℃ to +85℃ Temperature Range Applications  Digital Set-top Box (STB)  Digital Video Recorder (DVR)  Tablet Personal Computer (Pad)  Portable Media Player (PMP)  Flat-Panel Television and Monitor  General Purposes The H9108 is a high frequency, synchronous, rectified, step-down, switch-mode converter with internal power MOSFETs. It offers a very compact and line regulation.The H9108 requires a minimal number of readily available, external components and is available in a space saving SOT23-6 package PR O solution to achieve a 2A continuous output current IN General Description over a wide input supply range, with excellent load SI Selection Table H9108 VOUT R1 R2 5.0V 50K 6.8K 3.3V 50K 11K 1.8V 50K 25K 1.5V 50K 33.3K 1.2V 50K 50K 1.0V 50K 75K Figure 1. Basic Application Circuit For VOUT=5V Ver1.3 1 Shanghai Siproin Microelectronics Co. H9108 18V,2A Synchronous Step-Down Converter Functional Block Diagram VIN + ∑ RSEN - VCC VCC REGULATOR CURRENT SENSE AMPLIFIER BOOST REGULATOR BS OSCILLATOR HS DRIVER + COMPARATOR - SW VCC REFERENCE EN ON TIME CONTROL CURRENT LIMIT COMPARATOR 1pF 1M 56pF LOGIC CONTROL 400k LS DRIVER + + GND - FB ERROR AMPLIFIER Figure 2. H9108 Block Diagram Pin Configuration 1 6 SW GND 2 5 VIN FB 3 4 EN PR O IN BS (SOT23-6) Pin Description PIN NAME FUNCTION 1 BS Bootstrap. A capacitor connected between SW and BST pins is required to form a floating supply across the high-side switch driver. GND 3 FB GROUND Pin Adjustable Version Feedback input. Connect FB to the center point of the SI 2 external resistor divider 4 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. 5 IN Power Supply Pin 6 SW Switching Pin Absolute Maximum Ratings Input Supply Voltage ······················································································ -0.3V to 18V Operating Temperature Range ········································································-40℃ to +85℃ FB Voltages ································································································ -0.3V to 6.0V Lead Temperature (Soldering, 10s) ············································································ 300℃ SW Voltage ···························································································-0.3V to (Vin+0.5V) Storage Temperature Range ········································································ -65℃ to 150℃ BS Voltage······················································································· (Vsw-0.3) to (Vsw+5V) Ver1.3 2 Shanghai Siproin Microelectronics Co. H9108 18V,2A Synchronous Step-Down Converter Electrical Charcteristics (VIN=12V, Vout=5V,TA = 25℃, unless otherwise noted.) Parameter Conditions MIN Input Voltage Range TYP 3.3 SupplyCurrent in Operation VEN=3.0V, VFB=1.1V 0.4 Supply Current in Shutdown VEN =0 or EN = GND 4 Regulated Feedback Voltage TA = 25℃, 4V≤VIN ≤18V 0.588 0.6 MAX unit 18 V 0.6 mA uA 0.612 V High-Side Switch On-Resistance 100 mΩ Low-Side Switch On-Resistance 70 mΩ VEN=0V, VSW=0V Upper Switch Current Limit Minimum Duty Cycle En Voltage Low PR O Oscillation Frequency En Voltage High Maximum Duty Cycle Minimum On-Time Minimum Off-Time 10 uA 3 A 0.6 MHz VENH 1.4 -- -- V VENL -- -- 0.9 V VFB=0.6V SI Thermal Shutdown 0 IN High-Side Switch Leakage Current Thermal Hysteresis 92 % 60 nS 90 nS 160 ℃ 20 ℃ Typical Performance Characteristics EFFICIENCY VS OUTPUT CURRENT (VOUT=5V) Ver1.3 OUTPUT VOLTAGE VS OUTPUT CURRENT (VOUT=5V) 3 Shanghai Siproin Microelectronics Co. H9108 18V,2A Synchronous Step-Down Converter STEADY STATE (VIN=12V,VOUT=1.2V,IOUT=100mA) OPERATION STEADY STATE OPERATION (VIN=12V,VOUT=1.2V,IOUT=1000mA) STRAT UP (VIN=12V,VOUT=1.2V) PR O IN LOAD TRANSIENT RESPONSE (VIN=12V,VOUT=1.2V,IOUT=100-1000mA,1A/uS) Functions Description Internal Regulator The H9108 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 SI voltage power MOSFET, and operates at a high 600K 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 0.6V. 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 1.5ms. Over Current Protection & Hiccup The H9108 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-Voltage (UV) threshold, typically 25% below the reference. Once a UV is triggered, the H9108 enters hiccup mode to Ver1.3 4 Shanghai Siproin Microelectronics Co. H9108 18V,2A Synchronous Step-Down Converter 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 H9108 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. Applications Information Setting the Output Voltage H9108 require an input capacitor, an output capacitor and an inductor. These components are critical to the performance of the device. H9108 are internally compensated and do not require external PR O IN components to achieve stable operation. The output voltage can be programmed by resistor divider. 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 SI are typically specified at 25°C, so ratings at maximum ambient temperature of the application should be requested from the manufacturer. 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: Under light load conditions below 100mA, larger inductance is recommended for improved efficiency. 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. Ver1.3 5 Shanghai Siproin Microelectronics Co. H9108 18V,2A Synchronous Step-Down Converter 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 IN 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, PR O 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. An example of 2-layer PCB layout is shown in Figure 4 for reference SI 6. Ver1.3 6 Shanghai Siproin Microelectronics Co. H9108 18V,2A Synchronous Step-Down Converter Package Description SI PR O IN SOT23-5 Outline Dimensions Ver1.3 7 Shanghai Siproin Microelectronics Co.