SI8251-IQ

Si8250/1/2 D I G I TA L P O W E R C O N T R O L L E R Features Single-Chip, Flash-based digital power controller Supports isolated and non-isolated applications Enables new system capabilities such as: - Adaptive dead-time control for higher efficiency - Nonlinear control for faster transient response - Self diagnostics for higher reliability - Full PMBus command set implementation for system connectivity Highly integrated control solution: High-speed digital hardware control loop In-system programmable supervisory processor Programmable system protection functions Hardware cycle-by-cycle current limiting and OCP External clock and frame synchronization inputs Performs system management functions such as external power supply sequencing and fan control/monitoring In-system Flash programmable Flash can also be used as NV memory for data storage Low cost, comprehensive development tool kit includes: Graphical, easy-to-use system design tools Integrated development environment In-system, on-line debugger Turnkey isolated 35 W digital half-bridge target board Typical Applications Isolated and non-isolated DC/DC converters AC/DC converters Fully Pb-free and ROHS compliant packages 32-pin LQFP 28-pin 5 x 5 mm QFN Temp Range: –40 to +125 ºC Pin Assignments: See page 23 32-pin LQFP GND VDD PH1 PH2 PH3 PH4 PH5 32 31 30 29 28 27 26 RST/C2CK IPK VSENSE GNDA VDDA VREF P1.0/VIN/AIN0 P1.1/AIN1 1 2 3 4 5 6 7 8 25 PH6 24 23 22 P0.0 P0.1 P0.2 P0.3 / XCLK P0.4 P0.5 P0.6 P0.7 Si8250/1/2 Top View 21 20 19 18 17 10 11 12 13 14 15 P1.6/AIN6 GND VDD 28-pin QFN 28 27 26 25 24 23 GND RST / C2CK IPK VSENSE GND VDD VREF P1.0/VIN/AIN0 1 2 3 4 5 6 GND 7 15 P0.7 22 P0.0 PH1 PH2 PH3 PH4 PH5 PH6 P1.7/AIN7/C2D P1.2/AIN2 P1.3/AIN3 P1.4/AIN4 P1.5/AIN5 16 9 21 20 19 P0.1 P0.2 P0.3/XCLK P0.4 P0.5 P0.6 Si8250/1/2 Top View 18 17 16 10 11 12 13 P1.6/AIN6 Description Si8250/1/2 provides all control and protection functions necessary to implement highly intelligent, fast response power delivery and management control systems for isolated and non-isolated power supplies. On-board processing capability enables intelligent control optimization for improved system performance and new capabilities such as serial connectivity via the PMBus or on-board UART. The Si8250/1/2 family is in-system Flash programmable enabling control and protection parameters such as system regulation and protection settings, start-up and shutdown modes, loop response, and modulation timing to be readily modified. The built-in high-speed control path provides loop updates every 100nS and provides pulse-by-pulse current limiting and over-current protection even while the internal CPU is disabled. The Si825x family is supported by the Si8250DK development kit, which contains everything required to develop and program power supply applications with the Si825x family of digital controllers. Patents pending Preliminary Rev. 0.8 3/06 Copyright © 2006 by Silicon Laboratories P1.7/AIN7/C2D P1.1/AIN1 P1.2/AIN2 P1.3/AIN3 P1.4/AIN4 P1.5/AIN5 14 8 9 Si8250/1/2 This information applies to a product under development. Its characteristics and specifications are subject to change without notice. S i8250/1/2 2 Preliminary Rev. 0.8 S i8250/1/2 TA B L E O F C O N T E N TS Section Page 1. Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 2. Benefits of Digital Power Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3. Product Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.1. System Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.2. Control Processor Functional Block Descriptions (Figure 1) . . . . . . . . . . . . . . . . . . . 16 3.3. System Management Processor Functional Block Descriptions . . . . . . . . . . . . . . . . 17 4. Design Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5. Example Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 6. Layout Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 7. Pin Descriptions—Si8250/1/2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 8. Ordering Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 9. Package Outline—32LQFP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 10. Package Outline—28QFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Document Change List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 Preliminary Rev. 0.8 3 S i8250/1/2 1. Electrical Specifications Table 1. Absolute Maximum Ratings* Parameter Ambient Temperature under Bias Storage Temperature Voltage on any Port0 Pin with respect to GND Voltage on all other pins with respect to GND Voltage on VDD with respect to GND Maximum total current through VDD or GND Maximum output current sunk by RST or any Port pin Conditions Min. –55 –65 –0.3 –0.3 –0.3 — — Typ. — — — — — — — Max. +135 +150 5.5 4.0 4.0 400 80 Units °C °C V V V mA mA *Note: Stresses above those listed under "2.1 Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only, and functional operation of the devices at those or any other conditions above those indicated in the operation listings of this specification is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability. Table 2. DC Electrical Specifications TA = –40 to +125 °C, VDD = 2.5 V, SYSCLK = 25 MHz, PLLCLK = 200 MHz unless otherwise specified. Parameter Supply Voltage Supply Current, all Peripherals Enabled Lockout mode supply current Digital Supply Current (shutdown) Digital Supply RAM Data Retention Voltage Conditions Min 2.25 Typ — 26 300 — 1.5 Max 2.75 — — TBD — Units V mA µA µA V Analog + digital supply current. Analog + digital supply current. (See Table 1 on page 4) Oscillator not running, VDD monitor disabled — — — — 4 Preliminary Rev. 0.8 S i8250/1/2 Table 3. Reference DAC Electrical Specifications TA = –40 to +125 °C, VDD = 2.5 V, SYSCLK = 25 MHz, PLLCLK = 200 MHz unless otherwise specified. Parameter Resolution LSB Size Integral Nonlinearity (INL) Differential Nonlinearity (DNL) Settling Time Turn-on Time Noise Power Supply Rejection Supply Current Shutdown Supply Current Conditions Min — — –2 –1.0 Typ — 2.44 — — 2 20 1 70 220 0.1 Max 9 — +2 +1.0 — — — — — — Units Bits mV LSB LSB µs µs mVPP db µA µA 1/2 LSB change from 0 to full scale — — 2 MHz BW — — — — Preliminary Rev. 0.8 5 S i8250/1/2 Table 4. ADC0 (12-Bit ADC) Specifications TA = –40 to +125 °C, VDD = 2.5 V, SYSCLK = 25 MHz, PLLCLK = 200 MHz unless otherwise specified. Parameter DC Accuracy Resolution Integral Nonlinearity Differential Nonlinearity Offset Error Full Scale Error Offset Temperature Coefficient Conditions Min Typ Max Units — — Guaranteed Monotonic — — Differential mode — — 12 — — ±3 3 TBD — ±2 ±1 — — — bits LSB LSB LSB LSB ppm/°C Dynamic Performance (10 kHz sine-wave Single-ended input, 0 to 1 dB below Full Scale, 200 ksps) Signal-to-Noise Plus Distortion Total Harmonic Distortion Spurious-Free Dynamic Range Conversion Rate Conversion Time in SAR Clocks Track/Hold Acquisition Time Throughput Rate Analog Inputs Input Voltage Range Input Capacitance Temperature Sensor Linearity Gain Offset Power Specifications Power Supply Current (VDD supplied to ADC0) Power-On Time Power Supply Rejection Operating Mode, 200 ksps After VREF settle, before tracking begins — — — 780 5 TBD — — — µA µs mV/V Notes 3, 4 Notes 3, 4 Notes 3, 4 (Temp = 0 °C) — — — ±TBD 1353 488 — — — °C µV/°C mV 0 — — 15 VREF — V pF Note 1 Note 2 — 1 — 13 — — — — 200 clocks µs ksps Up to the 5th harmonic — — — 64 83 –73 — — — dB dB dB Notes: 1. An additional 2 FCLK cycles are required to start and complete a conversion. 2. Additional tracking time may be required depending on the output impedance connected to the ADC input. 3. Represents one standard deviation from the mean. 4. Includes ADC offset, gain, and linearity variations. 6 Preliminary Rev. 0.8 S i8250/1/2 Table 5. ADC1 Specifications TA = –40 to +125 °C, VDD = 2.5 V, SYSCLK = 25 MHz, PLLCLK = 200 MHz unless otherwise specified. Parameter Sampling Frequency Conditions ADCSP = 0 ADCSP = 1 Min — — — 4 Typ 10 5 — — — — — — 5 3 5 0.1 — Max — — 6 20 +31 1.3 +2 +1 — — — — 3 Units Msps Resolution LSB Size Differential Input Voltage Range Common-mode input voltage range Integral Nonlinearity Differential Nonlinearity Gain Error Offset Error Input Bias Current Standby Mode Supply Current Operating Mode Supply Current disabled Note 1 Bits mV LSB V LSB LSB % mV µA µA mA –32 0.8 –2 –1 — — — — — Notes: 1. LSB size (mV) is programmable using the RES[3:0] bits in the ADC1CN register. Table 6. DSP Filter Engine Electrical Specifications TA = –40 to +125 °C, VDD = 2.5 V, SYSCLK = 25 MHz, PLLCLK = 200 MHz unless otherwise specified. Parameter Resolution1 Dithering2 Standby Mode Supply Current Conditions Min — — Typ — — 0.1 Max 9 6 — Units Bits Bits µA disabled — Notes: 1. Internal word length = 22 bits. 2. Up to a total 15 bits of resolution when dithering is enabled. Preliminary Rev. 0.8 7 S i8250/1/2 Table 7. Peak Current Limit Detector Electrical Specifications TA = –40 to +125 °C, VDD = 2.5 V, SYSCLK = 25 MHz, PLLCLK = 200 MHz unless otherwise specified. Parameter IPK Input to DPWM Output Latency Threshold Detector Voltage Conditions 10 mV Overdrive VT[3:0] = 0000 VT[3:0] = 0001 VT[3:0] = 0010 VT[3:0] = 0011 VT[3:0] = 0100 VT[3:0] = 0101 VT[3:0] = 0110 VT[3:0] = 0111 VT[3:0] = 1000 VT[3:0] = 1001 VT[3:0] = 1010 VT[3:0] = 1011 VT[3:0] = 1100 VT[3:0] = 1101 VT[3:0] = 1110 VT[3:0] = 1111 Min — 35 85 135 185 235 285 335 485 435 485 535 585 635 685 735 785 — — — — — — — — — — Typ 45 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 0 5 10 20 0 20 40 80 4.5 0.1 0.1 100 Max — 65 115 165 215 265 315 365 415 465 515 565 615 665 715 765 815 — — — — — — — — — — — — Units ns mV Hysteresis HYST[1:0] = 00 HYST[1:0] = 01 HYST[1:0] = 10 HYST[1:0] = 11 mV Blanking Time LEB[1:0] = 00, fPLL = 200 MHz LEB[1:0] = 01, fPLL = 200 MHz LEB[1:0] = 10, fPLL = 200 MHz LEB[1:0] = 11, fPLL = 200 MHz ns Input Capacitance Input Bias Current Shutdown Supply Current Active Supply Current Enable bit = 0 IIN = (Vt + 100 mVpp), 1.5 MHz sq. wave pF µA µA µA — — 8 Preliminary Rev. 0.8 S i8250/1/2 Table 8. DPWM Specifications TA = –40 to +125 °C, VDD = 2.5 V, SYSCLK = 25 MHz, PLLCLK = 200 MHz unless otherwise specified. Parameter Clock Frequency Conditions DPWMSP[4:3] = 00 DPWMSP[4:3] = 01 DPWMSP[4:3] = 1x Min — — — — — 5 20 40 3 — — — — Typ — — — — — — — — — — 75 40 — Max 200 50 25 9 15 — — — — 5 — — 0.1 Units MHz Resolution No dithering Dithering enabled Bits Time Resolution DPWMSP[4:3] = 00 DPWMSP[4:3] = 01 DPWMSP[4:3] = 1x ns SYNC Pulse set-up time PH Rise, Fall Time Output Resistance High Output Resistance Low Shutdown Supply Current SYNC signal minimum LOW time before positive transition 50pF on pin IOUT = –5 mA IOUT = 8 mA DPWM clock cycles ns Ω Ω µA Table 9. Bandgap Voltage Reference Specs TA = –40 to +125 °C, VDD = 2.5 V, SYSCLK = 25 MHz, PLLCLK = 200 MHz unless otherwise specified. Parameter Output Voltage Temperature Stability Turn-on Response Conditions Min — –1 Typ 1.20 — 6.5 2 2 60 30 50 Max — +1 — — — — — — Units V % ms µs µV (RMS) µA µA dB (0.01%, 4.7 µF) no load — — — — — — Noise Bandgap Current Reference Buffer Current Power supply rejection 4.7 µF Preliminary Rev. 0.8 9 S i8250/1/2 Table 10. Comparator0 Specifications TA = –40 to +125 °C, VDD = 2.5 V, SYSCLK = 25 MHz, PLLCLK = 200 MHz unless otherwise specified. Parameter Vin Low-Speed Supply Current Full-speed Supply Current Hysteresis Conditions Min 0 — — Typ — 8 225 0 7 14 28 0 –7 –14 –28 180 25 5 50 5 Max VDD — — — — — — — — — — — — — — — Units V µA µA mV CP0HYP[1:0] = 00 CP0HYP[1:0] = 01 CP0HYP[1:0] = 10 CP0HYP[1:0] = 11 CP0HYN[1:0] = 00 CP0HYN[1:0] = 01 CP0HYN[1:0] = 10 CP0HYN[1:0] = 11 — — — — — — — — — — — — — Response Time Low Power Mode, 25 mV Overdrive High-Speed Mode, 25 mV Overdrive ns Input Capacitance CMRR Input offset pF db mV 10 Preliminary Rev. 0.8 S i8250/1/2 Table 11. Reset Electrical Characteristics TA = –40 to +125 °C, VDD = 2.5 V, SYSCLK = 25 MHz, PLLCLK = 200 MHz unless otherwise specified. Parameter RST Output Low Voltage RST Input High Voltage RST Input Low Voltage RST Input Pull-up Current VDD POR Threshold Missing clock detector timeout Reset time delay Conditions IOL = 8.5mA, VDD = 2.5V Min — 0.7 x VDD — Typ — — — 25 2.1 250 — Max 0.7 — 0.3 x VDD TBD 2.2 650 — Units V V V µA V µs µs RST = 0.0 — 2.0 Time from last system clock rising edge to start of reset Delay between release of any reset source and code execution at location 0x0000 — 5.0 Minimum RST Low time to generate a System Reset VDD monitor turn-on time VDD monitor supply current 6.5 100 — — — 40 — — — µs µs µA Table 12. Flash Electrical Characteristics TA = –40 to +125 °C, VDD = 2.25 V – 2.75 V, SYSCLK = 25 MHz, PLLCLK = 200 MHz unless otherwise specified. Parameter Flash Size Conditions Si8250 Si8251, Si8252 Min 32768 (1) Typ — — 100 K — — — Max — — — — 48 114 Units bytes 16383(1) 10 K TBD Endurance Read Cycle Time Erase Cycle Time Write Cycle Time 50 MHz System Clock 50 MHz System Clock Erase/Write ns ms µs 32 76 Notes: 1. The last 512 bytes of memory are reserved. Preliminary Rev. 0.8 11 S i8250/1/2 Table 13. Port I/O DC Electrical Characteristics TA = –40 to +125 °C, SYSCLK = 25 MHz, PLLCLK = 200 MHz unless otherwise specified. Parameters Port0 Input Voltage Tolerance Conditions push-pull open-drain Min — — — Typ — — — — — VDD – 0.8 — — 1.25 — — — 20 Max VDD + 0.7 5.5 VDD + 0.7 — — — 0.6 0.1 — — (0.3) VDD ±10 50 Units V Port1 Input Voltage Tolerance Output High Voltage IOH = –3 mA, Port I/O push-pull IOH = –10 µA, Port I/O push-pull IOH = –10 mA, Port I/O push-pull Output Low Voltage IOL = 8.5 mA IOL = 10 µA IOL = 25 mA Input High Voltage Input Low Voltage Input Leakage Current Weak Pullup Off Weak Pullup On, VIN = 0 V VDD – 0.4 VDD – 0.1 — — — — (0.7) VDD — — — V V V V µA Table 14. PLL Specifications TA = –40 to +125 °C, VDD = 2.5 V, SYSCLK = 25 MHz, PLLCLK = 200 MHz unless otherwise specified. Parameter Stabilization Time Input Frequency Range PLL Frequency Cycle-to-cycle jitter Supply current Shutdown current Conditions Min — 15 — — — — Typ 30 — 200 250 15 0.1 Max — 25 — — — — Units µs MHz MHz ps mA µA 12 Preliminary Rev. 0.8 S i8250/1/2 Table 15. 25MHz Oscillator Specifications TA = –40 to +125 °C, VDD = 2.5 V, SYSCLK = 25 MHz, PLLCLK = 200 MHz unless otherwise specified. Parameter Frequency Start-up time Power supply sensitivity Temperature coefficient Supply current Shutdown current Conditions Min — — — — — — Typ 24.5 100 0.3 50 450 0.1 Max — — — — — — Units MHz µs %/V PPM/°C µA µA Table 16. Low Frequency Oscillator (LFO) Specifications TA = –40 to +125 °C, VDD = 2.5 V, SYSCLK = 25 MHz, PLLCLK = 200 MHz unless otherwise specified. Parameter Frequency Start-up time Power supply sensitivity Temperature coefficient Supply current Shutdown current Conditions Min — — — — — — Typ 80 100 1.7 1000 4 0.1 Max — — — — — — Units kHz µs %/V PPM/°C µA µA Preliminary Rev. 0.8 13 S i8250/1/2 2. Benefits of Digital Power Control Digitally controlled power systems have the following key advantages over analog implementations: In-system programmability: Virtually all aspects of digital controller behavior can be changed in software locally or remotely, and without hardware modification. This benefits the system in several ways: Hardware designs can be segregated into base platforms (for example, by form factor or output power), and optimized to the end application in software. This lowers development costs by reducing the total number of hardware designs required to address a given application segment. The controller's ability to readily accept change makes possible low-cost, custom power supply versions with relatively short lead-time. The cost and risk of field configuration and/or updating is greatly reduced, lowering the overhead associated with customer support. More advanced control algorithms: Power supply design with fixed-function analog components leads to many performance trade-offs. For example, analog compensator design routinely trades stability for higher loop bandwidth, and places the required poles and zeros using passive components. The "ifthen-else" decision-making capability of digital control can change loop bandwidth as needed for optimum control response. For example the controller can operate the compensator at a relatively low bandwidth during steady-state operation, but significantly extend bandwidth during a transient. This adaptive response concept can be applied to improve other operating parameters such as efficiency. Power Efficiency Optimization: In a switched mode power supply, it is desirable to maintain high power efficiency over a wide range of loads. Software algorithms can optimize efficiency at every point of line and load. For example, the software can adjust dead time with changes load, disable synchronous rectification at low loads, or take other measures to maximize efficiency. Higher operating precision: Switch timing, control response and protection setting thresholds in analog systems are typically determined by the values of external passive components. These components typically have a wide tolerance and vary with temperature and time. Designers must allow for these tolerances when considering worst case operating conditions. Digital control offers tighter parameter tolerances with greatly reduced temperature/time variations resulting in improved worst-case operating specifications. Power management and power delivery functions in a single package: Power management functions, such as external supply sequencing, PMBus communication support and fan control can be performed by the digital controller, eliminating dedicated external components. System connectivity: PMBus and other emerging communication protocols enable system processors to communicate with the power supply to obtain data and command action. For example, the system processor may request the power supply operating history, perform self-diagnostics or change system settings without taking the supply off-line. Communications with the system controller enables notification of a pending power supply failure, enhancing system reliability. This attribute also reduces the cost and complexity of field configurations and upgrades. Higher integration/smaller size/lower cost: Many discrete circuits can be transformed to lines of software code, eliminating components and saving cost. The digital controller can be used to execute self-diagnostic routines during production test thereby reducing test time and saving cost. The small physical size of the Si8250 in particular (5 x 5 mm) saves board space. 14 Preliminary Rev. 0.8 S i8250/1/2 3. Product Description System Management Processor 50MIPS 8051 CPU 2% 25 Mhz OSC, and LFO RESET CONTROL DEBUG PORT HARDWARE DEBUG INTERRUPT CONTROL 16/32 kB 4x 16-BIT TIMERS PORT 0 VDD SYSCLKIN Flash 1280 Byte RAM S MBus 3 CH PCA I/O PORT LATCHES UART MUX I/O (8) PORT 1 VSENSE I/O (8) ADC REGISTERS & LIMIT DETECTORS 12-BIT 200 Ksps ADC AUTO SCAN LOGIC 8 TEMP SENSOR VSENSE VSENSE 10 MHz ADC VREF DSP FILTER ENGINE u(n) REFDAC VREF IPK Pulse-by-Pulse Current Limiter and OCP ICYC O CP MULTIPHASE DPWM GATE CONTROL (6) Control Processor Si8250/1/2 Figure 1. Functional Block Diagram System Management Processor VDD SYSCLKIN DEBUG PORT Digital Peripherals: - UART - SMBus Port - 4 x 16-Bit Timers - 3 Ch PCA (PWM) - I/O Port Latches PORT 0 I/O CROSSBAR 50MIPS 8051 CPU and Memory 16 General-Purpose Analog/Digital I/O Lines ADC 0 12-Bit, 200Ksps 10-Channel VSENSE TEMP SENSOR PORT 1 Analog Input (e.g. average current) Digital Ouput (e.g. fan speed control) POWER STAGES VSENSE VSENSE ADC1 10Msps VREF REFDAC DSP FILTER ENGINE u(n) SUPPLY INPUT VOLTAGE MULTIPHASE DPWM SWITCHES AND MAGNETICS OUTPUT FILTER VOUT VREF IPK Pulse-by-Pulse Current Limiter and OCP Control Processor ICYC O CP U p to 6 Gate Control Outputs GATE DRIVERS Si8250 Peak Current Signal (e.g. CT) Figure 2. Si8250 Top-Level Block Diagram Preliminary Rev. 0.8 15 S i8250/1/2 3.1. System Operation Figure 2 shows the Si8250/1/2 controlling a nonisolated DC/DC converter operating in digital voltage mode control. The output voltage signal connects to the VSENSE input through a resistive divider, limiting the common mode voltage range applied to ADC1 to a maximum of VREF. The equivalent resistance of the divider and the capacitor form an anti-aliasing filter with a cutoff frequency equal to ADC1 sampling frequency of divided by 2 (the amplitudes of frequencies above fS/2 must be minimized to prevent aliasing). Differential ADC1 and the DSP Filter Engine together perform the same function as an analog error amplifier and associated RC compensation network. ADC1 digitizes the difference between the scaled output voltage and a programmable reference voltage provided by the REFDAC. The ADC1 output signal is frequency compensated (in digital domain) by the DSP Filter Engine. The resulting output from the DSP Filter Engine is a digital code that represents the compensated duty cycle ratio, u(n). The digital PWM generator (DPWM) directly varies output timing to the external gate drivers based on the value of u(n) until the difference between VSENSE and ADC1 reference level is driven to zero. Sensing circuitry within the power stages (current transformer, sense amp, etc.) provides a signal representative of inductor or transformer current. This signal connects to the pulse-by-pulse current limiting hardware in the Si8250/1/2 via the IPK input pin. This current limiting circuitry is similar to that found in a voltage mode analog PWM. It contains a fast analog comparator and a programmable leading-edge blanking circuit to prevent unwanted tripping of the current sensing circuitry on the leading edge of the current pulse. Current limiting occurs when the sensed current exceeds the programmed threshold. When this occurs, the on-going active portions of the PWM outputs are terminated. A programmable OCP counter keeps track of the number of consecutive current limit cycles, and automatically shuts the supply down when the accumulated number of limit cycles exceeds the programmed maximum. The System Management Processor is based on a 50 million instruction per second (MIPS) 8051 CPU and dedicated A/D converter (ADC0). ADC0 digitizes key analog parameters that are used by the MCU to provide protection, as well as manage and control other aspects of the power system. On-board digital peripherals include: timers, an SMBus interface port (for PMBus or other protocols); and a universal asynchronous receiver/transmitter (UART) for serial communications, useful for communicating across an isolation boundary. The System Management Processor serves several purposes, among these are: 1. Continuously optimizes Control Processor operation (e.g. efficiently optimization) 2. Executes user-specific algorithms (e.g. support for proprietary system interfaces) 3. Provides regulation for low-bandwidth system variables (e.g. VIN feed-forward) 4. Performs system fault detection and recovery 5. Provides system housekeeping functions such as PMBus communication support 6. Manages external device functions (e.g. external supply sequencing, fan control/monitoring) The Si8250/1/2 system development requires using the Si8250DK, a comprehensive development kit providing all required hardware and software for control system design. It comes complete with pre-written and verified application software, and a set of tools that enable the user to adapt this software to the end application. It also includes a turnkey isolated half-bridge DC/DC converter based on the Si8250/1/2 for evaluation and experimentation. 3.2. Control Processor Functional Block Descriptions (Figure 1) ADC 1: Differential input, 10 Msps control loop analogto-digital converter. ADC1 digitizes the difference between the Vsense input and the programmable voltage reference level from the REFDAC. ADC1 can be operated at either 5 Msps or 10 Msps and has a programmable LSB size to prevent limit cycle oscillation (Limit cycle oscillation can also be avoided using dithering to increase DPWM resolution). ADC1 has programmable conversion rates of 10 Msps and 5 Msps to accommodate a wide loop gain range. ADC1 also contains a hardware transient detector that interrupts the CPU at the onset of an output load or unload transient. The CPU responds by executing specific algorithms to accelerate output recovery. These algorithms may include increasing loop bandwidth or other measures. REFDAC: 9-bit digital-to-analog converter provides the output voltage reference setting. The REFDAC uses the on-board band gap as its voltage reference, or can be referenced to an external voltage reference source. REFDAC is used for output voltage calibration, margining and positioning. The CPU continuously manages the REFDAC during soft-start and soft-stop. DSP Filter Engine: This two-stage loop compensation filter is the functional equivalent of an active RC compensation in an analog control scheme. The first filter stage is a PID filter providing one pole and two 16 Preliminary Rev. 0.8 S i8250/1/2 zeros. The second stage is selectable: a two-pole lowpass filter (LPF) for the fastest possible response, or SINC (multiple zero) decimation filter for relatively quieter operation. The PID plus the LPF result in a three pole, two zero composite filter, while the PID plus the SINC results in a single pole, multiple zero composite filter. The SINC filter provides zeros at intervals equal to fS/(2*DEC) where DEC is the decimation ratio (i.e. ratio of input to output sampling rate). DEC is a softwareprogrammable parameter, and can be programmed such that zero placement occurs that the PWM frequency and its harmonics. This creates more than 100 db attenuation at these frequencies providing lower system noise levels. The end-to-end response of the filter is defined using only six software parameters, and can be reprogrammed during converter operation to implement nonlinear control response for improved transient resolution. As described in the ADC1 section above, limit cycle oscillation can be avoided by increasing ADC1 LSB size to allow the DPWM LSB to fit within a single ADC1 output code (i.e. zero-error bin). However in some applications, it may not be desirable to lower ADC1 sensitivity. For such applications, limit cycle oscillation can be avoided by dithering the DPWM output. The DSP Filter Engine contains a pseudo-random, broadband noise generator - mixing this noise into the filter output randomly moves the gate control output(s) over a range of 1 LSB, such that the time-averaged resolution of the DPWM is increased. The filter response is programmed using S-domain design tools included in the Si8250DK development kit, greatly minimizing software writing tasks. Pulse-by-pulse Current Limiter/OCP: High-speed comparator with 4-bit DAC threshold generator and 2-bit programmable leading-edge blanking delay generator. The comparator output causes the DPWM to terminate the on-going portions of the active outputs when the peak current signal applied to the IPK input exceeds the threshold setting. Hardware performs an OCP supply shutdown when the number of consecutive current limit events equals a programmed maximum. DPWM: Output generator may be programmed for pulse width (PWM) or phase-shift modulation using design tools contained in the Si8250DK design kit. The DPWM may be modulated by the front-end of the Control Processor (ADC1 and DSP Filter Engine); or by the CPU. The DPWM has individually programmable stop states for supply off (disable) and OCP. Software bypass mode allows the CPU to force selected outputs high or low while the remaining outputs continue normal operation. The DPWM includes an external SYNC input and ENABLE input, both of which can be connected to the I/O pins. The Enable is a logic input used to turn the power supply on and off. It can be configured to be active high or active low. The SYNC input allows the start of each switching cycle to be synchronized to an external clock source, including another Si8250/1/2. 3.3. System Management Processor Functional Block Descriptions ADC0: Self-sequencing, 10-input, 200 Ksps analog-todigital converter. This general-purpose ADC acquires other analog system parameters for supplemental control by the CPU (e.g. dead time control using average input current as the control variable). ADC0 also converts the output of the on-board temperature sensor. Eight of the ten analog inputs may be connected to the I/O pins for external interface. The remaining two analog inputs (Vsense and Temp Sensor) are internally connected. When placed in Auto Sequencing mode, ADC0 automatically converts, stores and limit-checks each analog input, and interrupts the CPU when a converted result is outside of its programmed range. This feature greatly facilitates protection functions because all measurement and comparison operations are automated. Temperature Sensor: This sensor measures the die temperature of the Si8250/1/2. It can achieve 3 C accuracy with a single-point calibration and 1 C with a two-point calibration. The temperature output signal is digitized by ADC0. 8051 CPU: 50MIPS CPU core with 1K of SRAM and up to 32 kB of Flash memory. This processor has its own on-board oscillator and PLL, reset sources and realtime in-system hardware debug interface eliminating the need for external processor supervisors, timebases, and "emulators". The CPU has an external interrupt (INT0/) that can be connected to an external device via the I/O pins. When interrupted, the CPU suspends execution of the current task, and immediately vectors to an interrupt service routine specifically designed to handle the interrupting device. Digital peripherals: Peripherals include: four 16-bit timers, a three-channel programmable counter array (PCA), each channel useful as a PWM, an SMBus port useful as a PMBus interface, a UART (useful as a serial data port for isolated applications, and two 8-bit I/O port latches for logic control outputs. Preliminary Rev. 0.8 17 S i8250/1/2 4. Design Tools The Si8250DK development kit (Figure 3) contains everything required to develop applications with the Si825x family of digital power controllers. This kit supports all phases of power supply development from controller design through real-time system debugging. It also includes a turnkey, 35 W isolated DC/DC target board for evaluation and experimentation. Figure 3. Si8250DK Development Kit Figure 5. Timing Design Tool (Top) and Buck Regulator Compensation Tool (Bottom) The tool set enables the user to configure pre-written application software included in the kit to his application using a set of PC-based graphical user interface (GUIs). These GUIs (Figure 5) allow the user to quickly and easily specify and verify system timing, loop compensation and protection settings, and compile and download the resulting code into the Si8250/1/2 (Figure 4). Figure 4. Software Download to Si8250 Mounted in Power Supply 18 Preliminary Rev. 0.8 S i8250/1/2 5. Example Applications Isolated DC/DC Converter: A 35 W, 400 kHz Si8250-based half bridge converter is shown in Figure 6. This circuit is the same as that of the target (evaluation) board shipped in the Si8250DK development kit. P3 DRIV ER 180nH VIN+ 0.010 1uH P4 2.2uF DRIV ER VOUT IRLR8113 6 x 100uF Ceramic .0.001 200 6:1 0.01uF 4.7 4.7 FDS3572 DRIVE R 4.7 200 33K IRLR8113 180nH IOUT Vsense 1K 120uF P2 DRIV ER P1 ~ 10K 4.7 ~ + 33K 2.2uF 3V3P 3.9K 7.5 IPK 0.01uF P3 P4 PH4 PH3 - VDD DC BAL AIN FDS3572 P2 PH2 PH1 VIN AIN P1 IIN AIN TX GND Isolator RX 3V3P VDDA GNDA VDDB GNDB 3V3P VDD GND 1.2nF 1K C8051F300 Microcontroller VIN- Si8250 Digital Controller Figure 6. Isolated Half-Bridge DC/DC Converter The Si8250/1/2 is located on the secondary-side of the power supply for optimum transient response. DPWM outputs PH3 and PH4 control gates of the synchronous rectifiers via a dual driver I.C. DPWM outputs PH1 and PH2 control the gates of the primary-side switching transistors with isolation provided by a Silicon Laboratories isolator. A current transformer circuit provides peak current sensing. Primary side analog parameters (input voltage and current and the filter node voltage) are digitized by a Silicon Laboratories C8051F300 microcontroller and passed to the Si8250/1/2 using the on-board UART through additional channels of the isolator I.C. to the Si8250/1/2. The Si8250/1/2 is uses the application software included with the Si8250DK development kit after being configured for the half-bridge application using the tools supplied in the kit. When power is applied, the CPU executes an internal reset followed by initialization of all parameters. The Si8250/1/2 remains in a low-power state, monitoring digitized VIN data from the primary-side MCU until VIN is within specified limits. At this time, the controller is fully enabled and executes soft-start by monitoring Vout while sequentially incrementing the loop voltage reference (REFDAC) until the supply output voltage is within specified range, at which time steady-state operation begins. During steady-state operation, the MCU operates in interrupt mode where hardware events divert program execution to specific routines in priority order. Preliminary Rev. 0.8 19 S i8250/1/2 Single Phase POL (point of load) converter: A 65 W, 400 KHz Si8252 based single phase POL converter block diagram is shown in Figure 7. DPWM outputs PH1 and PH2 control the gates of the buck and synchronous switching transistors. A lossless current sensing method that relies on the resistor and inductance of the inductor is used to measure the current for over current protection. The input voltage is measured using resistor divider network and analog input port AIN0 of 12bit, 200 kHz ADC0. DIFFERENTIAL AMPLIFIER Ipk VIN L LOAD Vout CIN C DRIVER DRIVER PH1 PH2 VIN +2.5 V VDD Vsense Ipk Ipk AIN0 Si8252 GND Figure 7. Single-phase POL Block Diagram When power is applied, the CPU executes an internal reset followed by initialization of all parameters. The Si8252 remains in a low-power state, monitoring digitized VIN data until VIN is within specified limits. At this time, the controller is fully enabled and executes soft-start by monitoring output voltage while sequentially incrementing the loop voltage reference (REFDAC) until the supply output voltage is within specified range, at which time steadystate operation begins. As in the previous half-bridge example, transient response is improved by adjusting loop gain at the onset of a transient (i.e. nonlinear control). The efficiency of the POL converter can be optimized over the complete load range by dynamically adjusting the dead-times. Typical efficiency simulation results for the POL are shown in Figure 8. In this case, the single-phase POL operates at a PWM frequency of 400 kHz with an output voltage of 3.3 V and an input voltage range of 10 to 15 V. The curve shows the efficiency with an input voltage of 12.0 V. 95 90 Eff ( Io) 85 80 0 5 10 Io 15 20 25 Figure 8. POL Efficiency 20 Preliminary Rev. 0.8 S i8250/1/2 6. Layout Considerations The mixed-signal nature of the Si8250/1/2 mandates clean bias supplies and ground returns. It is best to provide separate ground planes for analog, digital and power switch returns. These planes should tie together at only one point to eliminate the possibility of circulating ground currents. For best performance, the VDD supply should be decoupled from the main supply. The LQFP-32 package provides the best noise performance because it has separate analog and digital VDD and ground inputs (AVDD, AGND). As shown in Figure 9, the AVDD is decoupled by a filter consisting of a 1 Ω resistor in series with a 500 mA, 40 Ω ferrite bead and a parallel combination of a 10 uF with a 0.1 uF high-frequency bypass capacitor. All connections should be kept as short as possible. The VDDA and GNDA should be connected into their respective ground planes. The QFN-28 package shares analog and digital power with ground on the same pins. Power supply decoupling is shown in Figure 10. Again, all connections should be kept as short as possible. Ferrite bead 500 mA, 40 Ω 1Ω 2.5 V 10 uF 10 uF 0 .1 uF AVDD DVDD 0 .1 uF Si8250/1/2 AGND Keep trace AGND lengths as short as possible DGND Figure 9. Power Supply Connections for LQFP-32 Package Ferrite bead 500 mA, 40 Ω 1Ω 2.5 V 10 uF 0 .1 uF V DD Si8250/1/2 GND Keep trace lengths as short as possible Figure 10. Power Supply Connections for QFN-28 Package Preliminary Rev. 0.8 21 S i8250/1/2 In both cases, the bias supplies must be filtered using low ESR/ESL capacitors placed close to the IC pins. Thick copper traces should be connected to the bias pins (VDD, VDDA) and the ground pins (GND, GNDA) to reduce resistance and inductance. The copper routings from the drivers to the FETs should be kept short and wide, especially in very high frequency applications, to reduce inductance of the traces so that the drive signals can be kept clean. Connections between VSENSE and the output voltage must be kept absolutely as short as possible to minimize inductance and parasitic ringing effects. It is best to locate the Si8250/1/2 as close to the output voltage terminal as possible and use a Kelvin connection to ensure to difference in ground potential between the Si8250/1/2 and the output voltage ground return. Most applications will require access to the debug pins. These pins are susceptible to damage from electrostatic discharge (ESD). It is therefore recommended the debug circuit interface use the input protection circuitry shown in Figure 11. Si8250/1/2 Debug Pins (C2D, C2CK) 10 10 DEBUG CONNECTOR Figure 11. Debug Interface Pin Protection Circuit 22 Preliminary Rev. 0.8 2.5 V S i8250/1/2 7. Pin Descriptions—Si8250/1/2 32-pin LQFP GND VDD PH1 PH2 PH3 PH4 PH5 PH6 28-pin QFN 32 31 30 29 28 27 26 25 28 27 26 25 24 23 GND RST/C2CK IPK VSENSE GNDA VDDA VREF P1.0/VIN/AIN0 P1.1/AIN1 1 2 3 4 5 6 7 8 24 23 22 P0.0 22 P0.0 PH1 PH2 PH3 PH4 PH5 PH6 RST / C2CK P0.1 P0.2 P0.3 / XCLK P0.4 P0.5 P0.6 P0.7 1 2 3 4 5 6 GND 7 21 20 19 P0.1 P0.2 P0.3/XCLK P0.4 P0.5 P0.6 P0.7 IPK VSENSE GND VDD VREF P1.0/VIN/AIN0 Si8250/1/2 Top View 21 20 19 18 17 Si8250/1/2 Top View 18 17 16 15 10 11 12 13 P1.6/AIN6 10 11 12 13 14 15 16 P1.7/AIN7/C2D GND VDD P1.5/AIN5 P1.2/AIN2 P1.3/AIN3 P1.4/AIN4 P1.6/AIN6 P1.1/AIN1 P1.2/AIN2 P1.3/AIN3 P1.4/AIN4 P1.5/AIN5 Figure 12. Example Pin Configurations Table 17. Pin Descriptions Name RST/C2CK IPK VSENSE GND GNDA VDD VDDA VREF P1.0/VIN or AIN0 P1.1/AIN1 P1.2/AIN2 P1.3/AIN3 P1.4/AIN4 GND VDD P1.5/AIN5 P1.6/AIN6 P1.7/ AIN7/C2D QFN-28 Pin # 1 2 3 4 — 5 — 6 7 8 9 10 11 — — 12 13 14 LQFP-32 Pin# 1 2 3 — 4 — 5 6 7 8 9 10 11 12 13 14 15 16 Type D I/O AIN AIN AIN AIN AIN AIN AIN D I/O or AIN D I/O or AIN D I/O or AIN D I/O or AIN D I/O or AIN AIN AIN D I/O or AIN D I/O or AIN D I/O, DIN or AIN Description Reset input or bidirect debug clock Inductor current input Output voltage feedback input Ground Ground Power supply input Power supply input External voltage reference input Port 1 I/O or scaled power supply input voltage or ADC input 0 Port 1 I/O or ADC input 1 Port 1 I/O or ADC input 2 Port 1 I/O or ADC input 3 Port 1 I/O or ADC input 4 Ground Power supply input Port 1 I/O or ADC input 5 Port 1 I/O or ADC input 6 Port 1 I/O or ADC input 7 or C2 Data Preliminary Rev. 0.8 P1.7/AIN7/C2D 14 8 9 9 23 S i8250/1/2 Table 17. Pin Descriptions (Continued) Name P0.7 P0.6 P0.5 P0.4 P0.3/XCLK P0.2 P0.1 P0.0 PH6 PH5 PH4 VDD GND PH3 PH2 PH1 QFN-28 Pin # 15 16 17 18 19 20 21 22 23 24 25 — — 26 27 28 LQFP-32 Pin# 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Type D I/O D I/O D I/O D I/O D I/O D I/O D I/O D I/O DOUT DOUT DOUT AIN AIN DOUT DOUT DOUT Port 0 I/O Port 0 I/O Port 0 I/O Port 0 I/O Port 0 I/O Port 0 I/O Port 0 I/O Port 0 I/O or bidirectional debug data Phase 6 switch control output Phase 5 switch control output Phase 4 switch control output Power supply input Ground Phase 3 switch control output Phase 2 switch control output Phase 1 switch control output Description Pin Functions: RST/C2CK: CPU reset or debug tool clock. Driving this pin low resets the CPU. This pin is also clocked by the USB debug adaptor during debug. IPK: Input to the peak current detector for pulse-by-pulse current limiting and over-current protection shutdown control. VSENSE: ADC1 inverting input. This is the voltage feedback input for the Si8250. The maximum allowable signal is VREF. GND: Digital ground for the 32LQFP package, and the main ground for the 28MLP package. GNDA: Analog ground for 32LQFP only. VDD: Digital supply voltage for the 32LQFP package, and main supply voltage for the 28MLP package. VDDA: Analog supply for 32LQFP only. P1.0/VIN or AIN0: Programmable multifunction I/O pin. This pin can be software configured to be either a Port 1 digital input or output, or an ADC0 input at AMUX address 0. If used in a non-isolated application, positive input supply voltage must be tied to this input through a resistor divider and anti-aliasing capacitor to minimize the frequencies above fS/2 (100Khz) to prevent aliasing. Isolated applications may use this input as general-purpose digital I/O or analog input. P1.1 or AIN1–P1.7 or AIN7: Programmable multifunction I/O pins. These pins can be software configured to be a Port 1 digital input or output, or an ADC0 input. P1.7 also serves as the debug data input (C2D) and is used during debug by the USB debug adaptor. P1.7 may be used as general-purpose digital I/O when not in debug mode. Any of the digital peripherals may be programmed to connect to these pins. P0.0–P0.7: Programmable multifunction I/O pins. These pins can be software configured to be either a Port 1 digital input or output, or an ADC0 input. Any of the digital peripherals (including the ENABLE input) may be programmed to connect to these pins. P0.3 may be programmed to serve as an external (25MHz nominal) clock input. PH1–PH6: DPWM gate control (complementary drive) outputs. These signals connect to the MOSFET gates through an external gate driver. The output levels swing between ground and Vdd. 24 Preliminary Rev. 0.8 S i8250/1/2 8. Ordering Guide Ordering Number Flash Memory Number of PWM Outputs 6 6 6 6 3 3 UART Package Si8250-IQ Si8250-IM Si8251-IQ Si8251-IM Si8252-IQ Si8252-IM 32 kB 32 kB 16 kB 16 kB 16 kB 16 kB Yes Yes Yes Yes No No LQFP-32 QFN-28 LQFP-32 QFN-28 LQFP-32 QFN-28 Preliminary Rev. 0.8 25 S i8250/1/2 9. Package Outline—32LQFP Figure 13 illustrates the package details for the 32-pin LQFP version of the Si8250/1/2. Table 18 lists the values for the dimensions shown in the illustration. D D1 A2 E1 E A L b 32 A1 e PIN 1 IDENTIFIER 1 Figure 13. 32-pin LQFP Package Diagram Table 18. LQFP-32 Package Dimensions MM Min A A1 A2 b D D1 e E E1 — 0.05 1.35 0.30 — — — — — Typ — — 1.40 0.37 9.00 7.00 0.80 9.00 7.00 Max 1.60 0.15 1.45 0.45 — — — — — 26 Preliminary Rev. 0.8 S i8250/1/2 10. Package Outline—28QFN Figure 14 illustrates the package details for the 28-lead QFN version of the Si8250/1/2. Table 19 lists the values for the dimensions shown in the illustration. Bottom View 10 11 12 13 14 8 9 L 7 Side View A2 A DD BB A3 6 5 4 e D2 2 b D2 16 17 R 18 19 20 CC 6xe E E2 DETAIL 1 AA 2 1 DETAIL 1 28 27 26 25 24 23 22 E2 2 3 21 6xe D Figure 14. 28-lead Quad Flat No-lead (QFN) Package Diagram Table 19. QFN-28 Package Dimensions MM Min A A1 A2 A3 b D D2 E E2 e 0.80 0 0 — 0.18 — 2.90 — 2.90 — Typ 0.90 0.02 0.65 0.25 0.23 5.00 3.15 5.00 3.15 0.5 Max 1.00 0.05 1.00 — 0.30 — 3.35 — 3.35 — L N ND NE R AA BB CC DD Min 0.45 — — — 0.09 — — — — MM Typ 0.55 28 7 7 — 0.435 0.435 0.18 0.18 Max 0.65 — — — — — — — — Preliminary Rev. 0.8 A1 15 e 27 S i8250/1/2 DOCUMENT CHANGE LIST Revision 0.7 to Revision 0.8 Updated DPWM phase output drive-high and drivelow resistance in Table 8, “DPWM Specifications,” on page 9. 28 Preliminary Rev. 0.8 S i8250/1/2 NOTES: Preliminary Rev. 0.8 29 S i8250/1/2 CONTACT INFORMATION Silicon Laboratories Inc. 4635 Boston Lane Austin, TX 78735 Tel: 1+(512) 416-8500 Fax: 1+(512) 416-9669 Toll Free: 1+(877) 444-3032 Email: productinfo@silabs.com Internet: www.silabs.com The information in this document is believed to be accurate in all respects at the time of publication but is subject to change without notice. Silicon Laboratories assumes no responsibility for errors and omissions, and disclaims responsibility for any consequences resulting from the use of information included herein. Additionally, Silicon Laboratories assumes no responsibility for the functioning of undescribed features or parameters. Silicon Laboratories reserves the right to make changes without further notice. Silicon Laboratories makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Silicon Laboratories assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. Silicon Laboratories products are not designed, intended, or authorized for use in applications intended to support or sustain life, or for any other application in which the failure of the Silicon Laboratories product could create a situation where personal injury or death may occur. Should Buyer purchase or use Silicon Laboratories products for any such unintended or unauthorized application, Buyer shall indemnify and hold Silicon Laboratories harmless against all claims and damages. Silicon Laboratories and Silicon Labs are trademarks of Silicon Laboratories Inc. Other products or brandnames mentioned herein are trademarks or registered trademarks of their respective holders. 30 Preliminary Rev. 0.8