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| Preliminary EN5312Q ENPIRION VIN UVLO Thermal Limit Current Limit Fully Integrated Voltage Mode Synchronous Buck PWM DC-DC Converter Module Rev 0.87 January , 2006 RoHS Compliant Product Overview The Ultra-Low-Profile EN5312Q is targeted to applications where board area and profile are critical. EN5312Q is a complete power conversion solution requiring only two low cost ceramic MLCC caps. Inductor, MOSFETS, PWM, and compensation are integrated into a tiny 4mm x 5mm x 1.1mm QFN package. Engineered to minimize all sources of converter noise, the EN5312Q eases design and layout constraints. 5 MHz switching frequency and internal type III compensation provides superior transient response. With a 1.1 mm profile, the entire layout can occupy as little as 28mm2 of board area. A 3-pin VID output voltage select scheme provides seven pre-programmed output voltages along with an option for external resistor divider. Output voltage can be programmed on-the-fly to provide fast, dynamic voltage scaling. ENABLE Soft Start P-Drive (-) PWM Comp (+) N-Drive VOUT Sawtooth Generator VSENSE (-) Error Amp (+) Switch VFB DAC VREF Voltage Select Package Boundry VS0 VS1 VS2 Product Highlights * Revolutionary integrated inductor * Total footprint as small as 28mm2 * Only two low cost MLCC caps required. * Very low solution profile at 1.1mm. * 4mm x 5mm x1.1mm QFN package * Wide 2.4V to 5.5V input range. * 1000mA output current. * Less than 1 A standby current. * High efficiency, up to 95%. * Very low ripple voltage; < 10mV * 3 Pin VID Voltage select scheme. * External divider option. * 5 MHz switching frequency * 2% accuracy over line, load, & temp. * Short circuit, UVLO, and thermal protection. * Stable with up to 100uF output capacitance. Typical Application Circuit ENABLE VIN 4.7F VSense VOUT 10F EN5312Q Vin Vout PFM VFB Voltage Select VS0 VS1 VS2 GND Figure 1. Typical application circuit. Applications * * * * * * Area constrained applications Set top box/home gateway Smart phones and PDAs. VoIP and Video phones Personal Media Players. Advanced Mobile Processors, DSP, IO, Memory, Video, Multimedia Engines. Rev. 0.87 - January 2006 EN5312Q Absolute Maximum Ratings Maximum Electrical Ratings Voltages on: VIN, VOUT Voltages on: VSENSE Voltages on: VS0-VS2 Voltages on: ENABLE Voltages on: VFB -0.3V -0.3V -0.3V -0.3V -0.3V -40C -65C Min Max 7.0V VIN + 0.3V VIN + 0.3V VIN + 0.3V 1.5V +85C +125C +125C +260C +260C Maximum Thermal Ratings Ambient operating range (Industrial Rated) Max Junction Temperature Storage Temperature Range Solder Temperature Range MSL3 (10 Sec) Reflow Peak Body Temperature Electrical Characteristics NOTE: VIN = 3.6V and TA = -40C to +85C unless otherwise noted. Typical values are at TA = 25C. CIN = 4.7uF, COUT=10uF PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNITS Operating Input Voltage Output Voltage VIN VS2 VS1 VS0 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 2.4 Vout 3.3 2.5 1.8 1.5 1.25 1.2 0.8 User Sel 5.5 V Vo V Maximum Output Current Output Current Shut-Down Current PFET Current Limit Feedback Pin Voltage Feedback Pin Input Current VS0-VS1, Enable Voltage Threshold VS0-VS2 Pin Input Current Operating Frequency PFET On Resistance NFET On Resistance Ripple Voltage Operating Junction Temperature Thermal Shutdown Thermal Shutdown Rev. 0.87 - January 2006 VIN = 5V, 0.6V mA A A V nA 0.0 1.4 0.4 VIN nA 5 300 300 10 125 150 15 MHz m m mV C C C www.enpirion.com COUT=4.7uF 1206 MLCC 2 Rev. 0.87 - January 2006 PARAMETER SYMBOL EN5312Q TEST CONDITIONS MIN TYP MAX UNITS Hysteresis Voltage Accuracy Voltage Regulation Soft-Start Operation Time to 90% Vout Tss All parts over line, load and Temp Any given part, Over load, line, temp Vout = 3.3V 1.6 2 1 % % mSec Pin Description ENABLE ENABLE 20 VS0 VS1 VS2 VS1 18 18 20 19 17 VS2 VIN VIN GND GND VOUT VOUT 1 2 3 4 5 6 10 7 8 9 16 15 14 13 12 11 VFB VSENSE NC NC NC NC VFB VSENSE NC NC NC NC 17 19 VS0 16 15 14 13 12 11 10 AGND 1 2 3 4 5 6 VIN VIN GND GND VOUT VOUT EN5312Q EN5312Q 9 8 7 Figure 2. Pin description, top view. VIN (Pin 1,2): Input voltage pin. Supplies power to the IC. VIN can range from 2.4V to 5.5V. GND: (Pin 3,4): Power ground. This pin is internally connected to bottom thermal/ground pad (AGND). Input and output filter capacitors should be connected to this pin. Good EMI design practice dictates that these pins not be connected to other ground connections. The large thermal pad on the bottom of the package should be the single point of contact to system ground. (refer to section on EMI layout consideration for more detail). VOUT (Pin 5,6,7): Regulated output voltage. NC (Pin 8,9,10,11,12,13,14): These pins should not be electrically connected to each other or to any external signal, voltage, or ground. One or more of these pins may be connected internally. VSENSE (Pin 15): Sense pin for preset output voltages. When using preset voltages connect this to VLOAD or as close to VLOAD as possible to ensure Rev. 0.87 - January 2006 VOUT NC NC NC NC NC NC Figure 3. Pin description, bottom view. the best regulation. When using external divider, connect this pin to VOUT. VFB (Pin 16): Feed back pin for external divider option. When using the external divider option (VS0=VS1=VS2= high) connect this pin to the center of the external divider. Set the divider such that VFB = 0.6V. VS0,VS1,VS2 (Pin 17,18,19): Output voltage select. VS0=pin19, VS1=pin18, VS2=pin17. Selects one of seven preset output voltages or choose external divider by connecting pins to logic high or low. Logic low is defined as VLOW 0.4V. Logic high is defined as VHIGH 1.4V. Any level between these two values is indeterminate. (refer to section on output voltage select for more detail). ENABLE (Pin 20): Output enable. Enable = logic high, disable = logic low. Logic low is defined as VLOW 0.4V. Logic high is defined as VHIGH VOUT 3 www.enpirion.com Rev. 0.87 - January 2006 1.4V. Any level between these two values is indeterminate. EN5312Q AGND (Bottom thermal/ground pad): System ground for single point grounding. Also functions as thermal pad to remove heat from package. Connect to surface or PWB internal ground plane. Functional Block Diagram VIN UVLO Thermal Limit Current Limit Ramp Control ENABLE Soft Start P-Drive (-) PWM Comp (+) N-Drive VOUT Sawtooth Generator VSENSE (-) Error Amp (+) Switch VFB DAC VREF Voltage Select Package Boundry VS0 VS1 VS2 Figure 4. Functional block diagram. Rev. 0.87 - January 2006 4 www.enpirion.com Rev. 0.87 - January 2006 EN5312Q Typical Performance Characteristics Vin = 3.6V 100 90 Efficiency (%) 80 3.3V 70 2.5V 1.8V 1.2V 60 100 200 300 400 500 600 Load Current (mA) 700 800 900 1000 Figure 5. Efficiency -vs- Load, Vin = 3.6V. Detailed Description Functional Overview The EN5312Q is a complete DCDC converter solution requiring only two low cost MLCC capacitors. MOSFET switches, PWM controller, Gate-drive, compensation, and inductor are integrated into the tiny 4mm x 5mm x 1.1mm package to provide the smallest footprint possible while maintaining high efficiency, low quiescent current, and high performance. The converter uses voltage mode control to provide the simplest implementation while also providing excellent transient response. The device operates at a 5 MHz switching frequency to make possible the very small components required to enable this unprecedented level of integration. Enpirion's proprietary power MOSFET technology provides very low switching loss at frequencies of 5 MHz and higher, allowing for the use of very small internal components, and very wide control loop bandwidth. Unique magnetics allow for high value inductor integrated into a low profile 1.1mm package. Integration of the inductor substantially reduces switching noise and design/layout issues normally associated with switch-mode DCDC converters. All of this enables much easier and Rev. 0.87 - January 2006 faster integration into various applications to meet demanding EMI requirements. Output voltage is chosen from seven preset values via a three pin VID voltage select scheme. An external divider option enables the selection of any voltage in the 3.3V to 0.6V range. This reduces the number of components that must be qualified and reduces inventory problems. The VID pins can be toggled on the fly to implement glitch free dynamic voltage scaling. Protection features include under-voltage lock-out (UVLO), over-current protection (OCP), short circuit protection, and thermal overload protection. Integrated Design Inductor for Low Noise Enpirion has introduced the world's first product family featuring integrated inductors. The EN5312Q family utilizes a low loss, planar construction inductor. The use of an internal inductor reduces noise associated with pulsed switching currents that would otherwise be present on the user circuit board. Integration minimizes the path impedance between the MOSFET switches and the inductor electrode, thereby reducing one of the 5 www.enpirion.com Rev. 0.87 - January 2006 key sources of conducted noise associated with switch-mode DCDC converters. The planar inductor construction orients the leakage magnetic fields in a direction that is orthogonal to those that can couple noise onto signal traces on the circuit board. Further, the package layout is optimized to reduce the electrical path length for the AC ripple currents that are the leading source of radiated emissions from DCDC converters. The integrated inductor significantly reduces switching noise effects, reduces parasitic effects that can harm loop stability, and makes layout very easy. EN5312Q Under Voltage Lockout During initial power up an under voltage lockout circuit will hold-off the switching circuitry until the input voltage reaches a sufficient level to insure proper operation. If the voltage drops below the UVLO threshold the lockout circuitry will again disable the switching. Hysteresis is included to prevent chattering between states. Enable The ENABLE pin provides a means to shut down the converter or enable normal operation. A logic low will disable the converter and cause it to shut down. A logic high will enable the converter into normal operation. In shutdown mode, the device quiescent current will be less than 1 uA. NOTE: This pin must not be left floating. Stable Over Wide Range of Operating Conditions The EN5312Q utilizes an internal type III compensation network and is designed to provide a high degree of stability over a wide range of operating conditions. One of the key features of this device is the ability to add supplementary capacitance to the output to further improve transient performance or reduce output voltage ripple. The EN5312Q is stable with up to 100uF of total output capacitance. The very high switching frequency allows for a very wide control loop bandwidth. Thermal Shutdown When excessive power is dissipated in the chip, the junction temperature rises. Once the junction temperature exceeds the thermal shutdown temperature the thermal shutdown circuit turns off the converter output voltage thus allowing the device to cool. When the junction temperature decreases by 15C, the device will go through the normal startup process. Soft Start Internal soft start circuits limit in-rush current when the device starts up from a power down condition or when the "ENABLE" pin is asserted "high". Digital control circuitry limits the VOUT ramp rate to levels that are safe for the Power MOSFETS and the integrated inductor. The soft start ramp rate is nominally 2mV/Sec. Over Current/Short Circuit Protection The current limit function is achieved by sensing the current flowing through a sense P-MOSFET which is compared to a reference current. When this level is exceeded the P-FET is turned off and the N-FET is turned on, pulling VOUT low. This condition is maintained for a period of 1mS and then a normal soft start is initiated. If the over current condition still persists, this cycle will repeat in a "hick-up" mode. Rev. 0.87 - January 2006 6 www.enpirion.com Rev. 0.87 - January 2006 EN5312Q Application Information Output Voltage Select To provide the highest degree of flexibility in choosing output voltage, the EN5312Q family uses a 3 pin VID, or Voltage ID, voltage select arrangement. This allows the designer to choose one of seven preset voltages, or to use an external voltage divider. Internally, the output of the VID multiplexer sets the value for the voltage reference DAC, which in turn is connected to the noninverting input of the error amplifier. This allows the use of a single feedback divider with constant loop gain and optimum compensation, independent of the output voltage selected. VS2 0 0 0 0 1 1 1 1 VS1 0 0 1 1 0 0 1 1 VS0 0 1 0 1 0 1 0 1 VOUT 3.3V 2.5V 1.8V 1.5V 1.25V 1.2V 0.8V User Selectable external divider. VSENSE must be connected to VOUT as indicated in Figure 6. ENABLE VIN 4.7uF VSense Vout Ra VFB Rb GND 10F Vin VOUT EN5312 VS0 VS1 VS2 Figure 6. External Divider. The output voltage is selected by the following formula: VOUT = 0.6V (1 + Ra Rb ) Ra must be chosen as 200K to maintain loop gain. Then Rb is given as: Rb = Table 1. Voltage select settings. 1.2 x10 5 VOUT - 0.6 Table 1 shows the various VS0-VS2 pin logic states and the associated output voltage levels. A logic "1" indicates a connection to VIN or to a "high" logic voltage level. A logic "0" indicates a connection to ground or to a "low" logic voltage level. These pins can be either hardwired to VIN or GND or alternatively can be driven by standard logic levels. Logic low is defined as VLOW 0.4V. Logic high is defined as VHIGH 1.4V. Any level between these two values is indeterminate. Dynamically Adjustable Output The EN5312Q is designed to allow for dynamic switching between the predefined VID voltage levels, or between the predefined output levels and an external divider. The inter-voltage slew rate is optimized to prevent excess undershoot or overshoot as the output voltage levels transition. The slew rate is identical to the soft-start slew rate of 2mV/uS. External Voltage Divider As described above, the external voltage divider option is chosen by connecting the VS0, VS1, and VS2 pins to VIN or logic "high". The EN5312Q uses a separate feedback pin, VFB, when using the Rev. 0.87 - January 2006 Input and Output Capacitors The input capacitance requirement is 4.7uF. Enpirion recommends that a low ESR MLCC capacitor be used. The input capacitor must use a X5R or X7R dielectric formulation. Y5V or equivalent dielectric formulations loose capacitance 7 www.enpirion.com Rev. 0.87 - January 2006 with frequency, bias, and temperature and are not recommended for switch-mode DC-DC converter input and output filter applications. The output capacitance requirement is a minimum of 10uF. The control loop is designed to be stable with up to 100uF of total output capacitance. Capacitance above the 10uF minimum should be EN5312Q added if the transient performance is not sufficient using the 10uF. Enpirion recommends a low ESR MLCC type capacitor be used. The output capacitor must use a X5R or X7R dielectric formulation. Y5V or equivalent dielectric formulations loose capacitance with frequency, bias, and temperature and are not recommended for switch-mode DC-DC converter input and output filter applications Layout Considerations and Application Circuits VS0 VS1 18 (+) (-) VIN 4.7F 20 19 17 VS2 EMI Considerations for Board Layout Integrated inductor and planar inductor construction go a long way toward reducing many of the sources of EMI, both conducted and radiated. However, care must still be taken to minimize potential sources of EMI. The package pin-out is carefully engineered to allow for the optimal layout. Input, output, and power ground planes are arranged such that the physical size of the AC current loops can be minimized and noisy power ground isolated. 1. Single point grounding: To limit AC current from flowing onto sensitive signal ground planes it is strongly recommended that a single point of contact be used for system ground. The thermal/ground pad located on the bottom of the package should be used for this common grounding point. The PGND pins, pins 3 and 4, are internally connected to the thermal/ground pad and so provides for an isolated power ground node for the input and output filter capacitors. Connect the input and output filter capacitors to these ground pins as shown in figure 7. Do not use these grounds for any other connections. ENABLE VIN VIN GND GND 1 2 3 4 5 6 AGND 16 15 14 13 12 11 10 VFB VSENSE NC NC NC NC 10F VOUT VOUT VOUT (-) Figure 7. Common point grounding schematic. 2. Pins 9, 11, 12, 13 are connected internally to VDRAIN. Keep all sensitive signal traces away from these pins. 3. Do not use vias for input and output filter caps. It is very important that input and output filter caps be placed on the same side of the board as the EN5312Q. At frequencies above 1 MHz, the skin penetration is too shallow for the AC signals to pass properly through a via. The AC currents will instead conduct along the surface of the planes and potentially couple noise. 7 8 9 VOUT NC NC NC (+) Rev. 0.87 - January 2006 8 www.enpirion.com Rev. 0.87 - January 2006 EN5312Q Typical Applications Circuits Example 1: Application utilizing preset output voltage, 1.8V. ENABLE VS0 VS1 18 VIN 20 19 17 VS2 4.7F VIN VIN GND GND 1 2 3 4 5 6 AGND 16 15 14 13 12 11 10 VFB VSENSE NC NC NC NC 10F VOUT VOUT 7 8 9 VOUT VOUT NC NC NC Figure 8. Application circuit with Vout = 1.8V. Example 2: Application using external divider to program VOUT ENABLE VS0 VS1 18 VIN 20 4.7F 19 17 VS2 VIN VIN GND GND 1 2 3 4 5 6 AGND 16 15 14 13 12 11 10 VFB VSENSE NC NC NC NC Rb=100K 10F VOUT VOUT Figure 9. Application demonstrating use of external divider output voltage programming; VOUT = 1.8V. 7 8 9 Ra=200K VOUT NC Rev. 0.87 - January 2006 9 NC NC VOUT www.enpirion.com Rev. 0.87 - January 2006 EN5312Q Design Considerations for Lead-Frame Based Modules Exposed Metal on Bottom Of Package Lead frame offers many advantages in thermal performance, in reduced electrical lead resistance, and in overall foot print. However, they do require some special considerations. In the assembly process lead frame construction requires that for mechanical support, some of the lead-frame cantilevers be exposed at the point where wire-bond or internal passives are attached. This results in several small pads being exposed on the bottom of the package. Only the AGND/Thermal pad and the perimeter pads are to be mechanically or electrically connected to the PC board. PWB solder mask must be used to prevent connection to the other pads. Figure 11 shows the shape and location of these metal pads as well as the mechanical dimension of the AGND/Thermal pad and the pins. The "grayed-out" area represents the area that should be protected by solder mask on the PWB. Thermal Pad. Connect to Ground plane Figure 10. Exposed metal and mechanical dimensions of the package . Figure 11 shows the recommended PWB solder mask openings. Rev. 0.87 - January 2006 10 www.enpirion.com Rev. 0.87 - January 2006 EN5312Q Figure 11. PWB Solder Mask Openings. N5312 XXXXX YYWW Rev. 0.87 - January 2006 11 www.enpirion.com Rev. 0.87 - January 2006 EN5312Q Contact Information Enpirion, Inc. 685 US Route 202/206 Suite 305 Bridgewater, NJ 08807 Phone: 908-575-7550 Fax: 908-575-0775 Enpirion reserves the right to make changes in circuit design and/or specifications at any time without notice. Information furnished by Enpirion is believed to be accurate and reliable. Enpirion assumes no responsibility for its use or for infringement of patents or other third party rights, which may result from its use. Enpirion products are not authorized for use in nuclear control systems, as critical components in life support systems or equipment used in hazardous environment without the express written authority from Enpirion. Rev. 0.87 - January 2006 12 www.enpirion.com |
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