The Infinite Bandwidth Company SEPTEMBER 1999 VOLUME 9 Introducing The Worlds' Simplest Surface Mount Switcher! The MIC4680 At A Glance Micrel's SuperSwitcherTM MIC4680 buck regulator is the first of a new family of products offering unparalleled output power in the smallest, simplest footprints. The MIC4680 is the industry's first surface mount switching regulator, providing more than 1A of output current in an SO-8 package with only four external components. Devices capable of providing the MIC4680's high output current have traditionally only been available in large, high power packages such as TO-220 and TO-263, which are more than five times the size of the MIC4680! One of the secrets of the MIC4680 is the use of a SO-8 package with half the thermal resistance of a regular SO-8. This is achieved by utilizing a concept which MOSFET manufacturers have been using for years: having four pins on one side of the package connected to the lead frame the die sits on, giving a low thermal resistance from the die to the outside world. This makes the MIC4680 not only a very flexible, but a more reliable and costeffective solution for the user. Up to 34VIN Simple buck regulator 4V to 34V input voltage operating range, 38V abs. max. Over 1A of continuous output current SO-8 package with twice the normal power handling capabilities Only four external components Replaces larger TO-220 and TO-263 solutions 200kHz switching frequency Nearly zero off current in shutdown, typically 2A Internally compensated with a typical small signal bandwidth of 20kHz Fixed output voltages of 3.3V and 5V as well as an adjustable version down to 1.25V Full current and thermal limit Operation temp of -40C to +125C >1A ON/OFF 68H 100F <5A Shutdown Current MIC4680 MIC4680 SO-8 SO-8 200KHz * * * * SO-8 with /2 the normal jA (63C/W) Runs cool More reliable Dissipates excess heat into ground plane 1 Contents MIC4680: Worlds' Simplest Surface Mount Switcher ..... 1 MIC5245: Newest Addition to the CapTM Family ......... 2 MIC2778: Power Supervisor IC for Portables ................. 3 MIC7201: Differential-to-Single-Ended Converter ......... 3 Micrel Semiconductor QwikRadioTM Receivers Update ..................................... 4 MIC2550: USB Transceiver for Mobile Products ............ 5 MIC39500: For Low Voltage, High Current FPGAs ....... 5 Application: Single-Cell Li-Ion Battery Charger ............. 6 MIC5014: Hot Plug Control Circuit ................................ 8 1849 FORTUNE DRIVE SAN JOSE, CA 95131 U.S.A. HTTP:// www.micrel.com/analogsolutions.html1 The World's Best LDO, the MIC5245 The MIC5245 is a world-class CMOS LDO and the latest addition to Micrel's family of Cap low-dropout regulators. It excels above and beyond its competitors in dropout voltage (100mV @ 100mA), ground current (100A over full load), and noise (30Vrms). The MIC5245 also has a unique push-pull output stage, allowing for extremely fast transient response. This output stage allows the regulator to sink and source current, which increases transient response speed significantly over traditional source-only LDOs. The lower dropout and noise, coupled with the fast transient response and fast turn-on time make the MIC5245 ideal for all cellular phone technologies. Key Features Stable with any capacitor, either ceramic or tantalum Output noise: 30Vrms Dropout voltage: 100mV @ 100mA Quiescent current: 100A (constant over load) Fast transient response: totem-pole output Fast turn-on time: 50s (COUT = 10F, CBYP = 10nF) Active shutdown clamp: fast turn-off time Totem Pole Output for Fast Transient Response V 2.7V to 6.5 VIN MIC5245 1 - 10F Cerami Tantalu c or m Outp ut Caps The Clever Stuff ON OFF 10nF Near zero off current Noise bypass for ultra-low noise MIC5245 The New Standard MIC5205 The Standard Low Noise LDO for the Past 5 Years Better Better Noise Noise Performance Performance 10dB! 10dB! MIC5205-3.0 VCO Phase Noise 2 TEL: 1.800.401.9572 FAX: 408.474.0159 MIC5245-3.0 VCO Phase Noise HTTP:// www.micrel.com/analogsolutions.html Voltage Supervisor Eliminates Low Battery Headaches Micrel's new MIC2778 voltage supervisor is the first supervisor optimized for tasks like low battery detection in portable devices. External resistors control the high and low trip points independently, making hysteresis completely adjustable. No more chattering, no more waiting for factory trimmed parts. Unlike most supervisors, the MIC2778 has a separate VDD pin, and the inputs and output can be pulled above VDD without adverse effects such as latch-up or excessive current draw. A built-in 140ms delay generator automatically de-glitches the output, which can be wire-OR'd with other signals. Low Battery Detected; System Shuts Down (But Not For Long!) Key Features Optimized for battery voltage monitoring Separate trip points for adjustable hysteresis 140ms (min.) delay generator de-glitches output Separate VDD input Active-low, open-drain output Inputs and output can be pulled above VDD Ultra-low supply current, 1.0A (typ.) Micrel's IttyBittyTM SOT23-5 package Inadequate Hysteresis Causes Chatter as Battery Voltage Recovers (Drives Users Crazy!) VBATT Adequate Hysteresis Prevents Chatter as Battery Voltage Low Battery Detected; Recovers System Shuts Down VBATT VHIGH VLOW VLOW VHYST 1 Micrel Competition 1 BAT_LOW BAT_LOW 0 0 TIME TIME Others Chatter at Low Battery Micrel Doesn't Chatter Differential to Single-Ended Conversion Made Simple 720 1 V+ MIC The MIC7201 combines a high performance rail-to-rail op amp with precision on-board resistors, creating a differential-to-single-ended converter all in Micrel's IttyBittyTM SOT23-5 package. No additional external components are required, and the output is biased to midsupply. Differential VS 2 Single-Ended 2 Key Features IN+ 50k 100k 3 OUT 1 100k IN- Key Specs 50k 4 50k MIC7201 V- Micrel Semiconductor IttyBittyTM SOT23-5 packaging No external components required 5 1MHz gain-bandwidth 2.8V to 15V supply voltage 0.5mA supply current 1849 FORTUNE DRIVE SAN JOSE, CA 95131 U.S.A. 3 QwikRadioTM Receivers Enable Wireless Applications Micrel's QwikRadio receivers provide wireless capability for previously wired applications by addressing the key drawbacks of RF -- cost and complexity RF Input 900 MHz 5V MICRF003 RF INPUT SHUTDOWN l Digita put Out DATA OUT No Trim Pots No Inductors QwikRadio -- Easy to Use In the past, RF receiver design was quite complex, requiring many external components and manual tuning. QwikRadio simplifies receiver design. Most of these requirements are now integrated on the chip, eliminating the need for manual tuning. This reduces the number external components down to just the antenna, a low-cost ceramic resonator, a couple of capacitors, and a power supply. "WAKE" function which can be used to enable the receiving system upon detection of incoming data. QwikRadio -- Low Cost QwikRadio combines low component count with much lower manufacturing cost (no production trimming) and competitive pricing. Key Specs QwikRadio -- No Trimming QwikRadio receivers are true single-chip receivers taking RFin and producing digital data-out with no trim-pots and just three external components. Production trimming adds cost and introduces quality concerns. Trim-pots drift over time, impacting reliability and range. 400MHz and 900MHz bands Data rate up to 20kbps Low power - 2.4mA continuous operation - 240A polled (10% duty cycle) Target Applications QwikRadio -- Low Power Micrel's all-CMOS integrated design offers significant power savings over bipolar or discrete implementations. Power savings can be further optimized on the MICRF002 and MICRF003, which are ideally suited to duty-cycling. In addition, both feature a Part Number Operating Frequency 300 - 440MHz MICRF001 MICRF011 MICRF002 MICRF022 MICRF003 MICRF033 4 X X TEL: Remote Switching -- lights, ceiling fans Remote Control -- set-top boxes Security Systems -- remote keyless entry, garage door openers Wireless Data -- utility metering, wireless keyboard and mouse, game controllers Data Rate 800 - 1000MHz X X X X Package 8-pin SOIC 4.8kbps 10kbps 10kbps 10kbps 20kbps 20kbps 8-pin DIP X 14-pin SOIC 14-pin DIP X X X X 16-pin SOIC 16-pin DIP X X X X X 1.800.401.9572 FAX: 408.474.0159 HTTP:// www.micrel.com/analogsolutions.html MIC39500 -- Powering Today's Low Voltage, High Current FPGAs Key Features Only 500mV Drop 5A, 2.5V LDO has guaranteed 500mV dropout 3-pin, 500mV dropout at full load and temperature 82% efficiency when operating off of 3V supply Only output capacitor required for operation Fast transient response 1% tolerance Fully protected with current limit, thermal shutdown and reversed lead insertion For lower current output, see the MIC39300 (3A), MIC39150 (1.5A) or MIC39100 (1A). (R) VOUT = 2.5V VIN = 3.0V 47F 3.3V I/O Voltage Altera is a trademark of Altera Corporation. Xilinx is a trademark of Xilinx, Inc. World's Only USB Transceiver for Mobile Products If you are planning to add USB communications to your next design, Micrel's MIC2550 saves you time and money! The MIC2550 employs a unique dual supply voltage design which allows it to operate down to 2.5V on the system side, and connect directly to the 5V USB voltage bus. With the MIC2550, you can operate your embedded controller or ASIC down to 2.5V without any additional voltage translation circuitry or special I/O cells, which would normally be necessary to support 3.3V USB signalling. In addition, the MIC2550 takes its operating power directly from the USB voltage bus, which decreases the power consumed from your system's battery. The MIC2550 will draw no more than 1A from your battery, enhancing battery life in today's mobile products. V CC VIF RCV VP Embedded Controller or ASIC Bidirectional differential-to-single-ended data conversion Integrated 3.3V LDO for termination Fully compliant to USB specification 1.1 Operates down to 2.5V Unique dual supply voltage design 2A quiescent current Low speed (1.5Mbps) and high speed (12Mbps) support Low power suspend mode Low height TSSOP package Transceiver supply current is direct from USB, not system supply, saving power consumption VM SUS SPD OE# MIC2550 2.5V - 5.25V Key Features VBUS V BUS VTRM D+ D+ D- D- Built-in LDO saves cost and space for providing 3.3V termination GND MIC2550 interface runs from same supply as ASIC, making input and output signals fully compliant Micrel Semiconductor 1849 FORTUNE DRIVE SAN JOSE, CA 95131 U.S.A. 5 Constant Current and Voltage for a Single-Cell LithiumIon Battery Charger by Jeff Dixon, Senior Applications Engineer Introduction (see manufacturer's specification). This method replaces a majority of the battery's charge as quickly as possible until the overcharge voltage threshold is reached. Float Charge-- maintain a constant voltage on an already charged cell. Not recommended for li-ion batteries. Overcharge--is a constant-voltage mode function that occurs consecutively after bulk charge. As the li-ion battery nears full capacity, the current decreases, and the battery's terminal voltage increases until it reaches its terminal voltage, typically 4.2V. When the current becomes low enough, less than trickle-charge normally, the charging cycle is complete. Li-ion cells should not be float charged. After the charge cycle is complete, the charger should be shut down. The Micrel MIC2179 is a current-mode, 200kHz, synchronous, buck (step-down) regulator. In this application, the MIC2179 is configured to provide both constant-current and constant-voltage for a 1-cell lithium battery charger. The current is sensed on the high side to avoid ground-bounce noise and the associated problems usually found in ground referenced circuits. Voltage is sensed using a simple voltage controller to reduce the parts count and provide a 0.5% voltage tolerance. The MIC2179 operates from a 4.5V to 16.5V input and has the following value-added features: dual-mode (skip-mode, PWM-mode) operation for high efficiency (up to 96%), low quiescent current (1.0mA in PWM mode, 600A in skip mode), internal current limit, thermal shutdown, undervoltage lockout (4.35V), low dropout (100% duty cycle) and simplified loop compensation (current-mode control). Theory of Operation The lithium-ion battery charger can be divided in to four blocks: a constant-current source, constant-voltage source, a switching regulator and an end-of-charge circuit. Lithium-Ion Charge States The three charge states for a lithium-ion battery are trickle charge, bulk-charge, and overcharge. Starting with a fully discharged battery, a lithium battery charger needs to change modes sequentially through these different charge states. Trickle charge--a constant-current mode used to bring a battery up to the cutoff voltage (VCUTOFF). The battery could be in deep discharge (2.5V to 2.7V per cell) for many reasons such as low state of charge, low ambient temperature, shorted cells, or high internal leakage. Bulkcharge--occurs while in constant-current mode and the charger is delivering the maximum allowable current to the battery Constant-Current Block To analyze this block, assume the constant-voltage block (U3 and supporting circuitry) is inactive. Starting with a discharged battery connected to the charger, the circuit acts like a constantcurrent source. An MIC2179 synchronous buck regulator provides the regulated power. The constant-current source's feedback loop consists of R7 (current-sense resistor), U2 (MIC6211 op amp), Q3 (VN2222 N-channel MOSFET), and the internal 1.24V feedback of U1 (MIC2179 synchronous buck regulator). First, the lithium-ion battery charger starts up in trickle-charge VIN 6.5V to 16.5V C1 68F 20V R12 100k 1% R1 100k 1% U1 6 5 13 HIGH = SHUTDOWN LOW = ENABLE Q1 VN2222 SW PWRGD MIC2179 PGND PWM SYNC COMP 8 FB SGND 9-12 HIGH = FAST CHARGE LOW = TRICKLE CHARGE TEL: D2 SS12 L1 68H 3, 4 1,2, 19,20 D1 MBRS140 C2 68F 20V R5 100 0.5% R7 0.1 1% 1.24V 7 R8 976 1% C5 0.01F BIAS 10k U2 Q2 VN2222 4 MIC6211 Q3 VN2222 C4 2 0.01F 3 4 2 Q4 VN2222 5 MIC6270 1 Single Li-Ion Cell 4 2 1 End Charge R11 75k TTL Logic Levels IOUT 120mA IOUT 120mA 5 R10 100k 1% C7 1 IN OUT D3 R3 10.2k 0.5% 1N4148 C6 0.01F COMP GND U3 LM3420M5-4.2 4.2V Voltage Controller Trickle Charge Resistor (120mA) 1.800.401.9572 FAX: 408.474.0159 U4 U5 VOUT 4.2V/1.2A 200k 1.1M R9 100k MIC6211 1 R4 1.15k 0.5% R6 976 1% 3 5 C3 0.01F 100k R13 4.2k 3 14 Fast Charge Resistor (1.2A) Charge Current 6 EN R2 10k 1% C2 6.8nF Shutdown 16,17 VIN 15 HTTP:// www.micrel.com/analogsolutions.html 1.24V R5 Bulk Charge Current = = 1.20A R3 || R4 R7 Constant-Voltage Source Once the battery's terminal reaches the 4.2V (1-cell lithiumion battery overcharge threshold), the constant-current source circuit is biased off. As the output voltage of the charger tries to go higher than 4.2V, the output of U3 (open-emitter configuration) biases D3 on. The feedback pin of the MIC2179 is now pulled-up toward the 4.2V VOUT rail, reducing duty cycle and maintaining output voltage regulation. The constant voltage feedback loop consists of U3 (LM3420A), D3, U1 (MIC2179), L1, R7, D2, and Q4. Because overvoltage conditions greatly reduce the life span of a lithium battery, an LM3420A was chosen for the voltage feedback loop to help maintain terminal voltage to 0.5%. In this charger design when the input supply is disconnected, diode D2 is reverse biased to prevent battery discharge. Q4 is bifunctional: it prevents the battery from being discharged when the input supply is removed; and it alleviates a race condition between the LM3420 and the start-up of the MIC2179 switching regulator. The LM3420 must be on before the output of the MIC2179 comes up. End-of-Charge Circuit The end-of-charge circuit is used to signal the microprocessor or another subsystem when the lithium-ion battery pack has reached the overcharge threshold. Again, in this 1-cell lithium-ion application, the overcharge threshold is 4.2V. Starting with a discharged battery and the charger in bulkcharge mode, the constant-current is decreasing and the voltage Micrel Semiconductor 4.5 1.4 4.0 1.2 3.5 Cell Voltage 1.0 3.0 0.8 2.5 2.0 0.6 1.5 Current 0.4 1.0 0.2 0.5 0 0 0.5 1.0 1.5 2.0 CHARGE CURRENT (A) 1.24V R5 Trickle Charge Current = = 121mA R3 R7 across the battery is increasing over time. The change in current versus voltage is a function of the changing internal impedance of the lithium-ion battery under charge. U5 is being used as a differential amplifier to monitor the output current by sensing the I*R drop across sense resistor R7. The gain of U5 is set to 102.5. The gain of U5 is set to maintain greater than 1.24V at its output down to a IOUT of greater than 120mA. U4 compares the output of U5 against the 1.24V bandgap reference on its non-inverting pin generated by the internal bandgap reference of MIC2179. In bulk-charge mode, the output of U5 is always higher than U4's reference voltage, thus maintaining a logic level low at the end-of-charge pin. Once R7 has less than a 12mV drop across it, the output of U5 can no longer sustain greater than 1.24V at its output. Now U4 has 1.24V on both its inputs. Next, the IOUT drawn by the battery reduces even further due to charging. Now the voltage at U4's inverting pin is lower than the 1.24V reference producing a logic level high at the output of U4, signaling an end-of-charge. The present industry-standard variable used to determine CELL VOLTAGE (V) mode. In trickle mode, the output of U2 (MIC6211) is on, biasing Q2 on, allowing the output of the MIC2179 to source 121mA of charging current to the battery. The intelligent system or microprocessor senses the low logic level at the output of U4 and places the charger into the bulk-mode charging state (1.2A). Sequencing from trickle mode to bulk mode is accomplished by applying a logic high on Q2's gate. In bulk-mode, current ramps up to 1.20A (for a 1-cell lithium application) through sense-resistor R7 (100m) creating a 120mV drop. Initially, the inverting input of U2 is lower than the noninverting input causing the output to go higher, increasing drive to Q3. This increases the current through the parallel combination of R3 and R4 until 1.24V is developed across them. The MIC2179 feedback pin senses the 1.24V and compares it to the internal 1.24V bandgap reference and reduces output duty cycle until 120mV is maintained across resistor R7. Finally, there is 120mV at both inputs of the MIC6211 (op amp), completing the negative feedback loop. Trickle charge and bulk charge is calculated using: 0.0 3.0 2.5 TIME (HRS) Typical lithium cell voltage vs. charging current lithium-ion battery end-of-charge is the current draw at about 90% charge (see graph below). The end-of-charge current is typically about C/10. A simple countdown timer circuit (not shown) is usually started upon reaching the end-of-charge state. Based on the individual manufacture specification, this completes the charge cycle. End-of-charge output current is calculated using a 1.24V reference: ( R9 = 1.24V ) R6 End-of-Charge Theshold I OUT x R7 1.24V is the reference for U4 pin 3 which is the end-of-charge comparator. Note: This circuit uses 120mA as an end-of-charge threshold. At the end of charge, the charging circuit should be shut down. It is not recommended to float charge li-ion cells for long periods of time. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 U.S.A. 7 Hot-Plug Control Circuit Handles 60V Power Rail for fully enhancing the gate of the FET. When power is applied, and/or the Shutdown input is released, the MIC5014 charges the gate of the FET through R3. Overcurrent protection is provided by R2, Q2, and Q3. When excessive output current flows, the resulting voltage drop across R2 turns on Q2, which then switches on Q3, the gate clamp transistor. Q3 discharges the MOSFET gate, disabling the hot-plug controller output. Q3 also provides the shutdown function. Although the MIC5014 is rated to 30V maximum operating voltage, it may be used in this configuration to well over 60V. Its supply voltage is clamped by the 15V (nominal) zener diode, which is current limited by R1. The power dissipated by the zener must be considered. The MIC5014 high-side FET driver can be used to perform all the necessary control and protection features for a hot-plug controller. This simple circuit may be added to a circuit board that is designed to hot-plug into a powered backplane. It enables the supply voltage slowly, preventing current surges that might propagate backward through the backplane and affect global power supply regulation. Additionally, it further protects the backplane by protecting against short-circuited cards. Key Features Adjustable output rise time Adjustable current limit High voltage operation Hot-swap compatible Fast reaction to short circuits (<10s) V (max) - 15V PZENER = IN R1 Circuit Operation R1 = The MIC5014 High Side N-Channel MOSFET driver provides a supervoltage (output voltage higher than the input voltage) suitable VIN(min) - 15V 10mA R2 = VIN 20V to 60V 15V R3 22 5 GATE 1 VIN 10 2 IN 0.44 ILIM Q1 MIC5014 MIC5014 SOURCE VIN R2 3 OUTPUT 330k 4 R1 2.7k Q2 10 SHUTDOWN ON Q3 47k OFF 47k 1N4002 High Voltage "Hot Swap" circuit schematic. When power is suddenly applied to VIN, the output is enabled slowly to prevent current surges and their resulting voltage transients Contact Micrel Semiconductor Corporate Headquarters Eastern US Sales Office 1849 Fortune Drive San Jose, CA 95131 USA Tel: (408) 944-0800 Fax: (408) 944-0970 93 Branch Street Medford, NJ 08055 USA Tel: (609) 654-0078 Fax: (609) 654-0989 Micrel Europe Sales Office Clere House 21 Old Newtown Road Newbury RG14 7DP UK Tel: +44 (1635) 524455 Fax: +44 (1635) 524466 8 TEL: Micrel Semiconductor Asia Ltd. 4F, Jinsol Building 826-14, Yeoksam-dong Kangnam-ku Seoul 135-080 Korea Tel: +82 (2) 3466-3000 Fax: +82 (2) 3466-2999 1.800.401.9572 FAX: 408.474.0159 Central US Sales Office, including Western US Sales Office Mexico, Central & South America 3250 Scott Boulevard Suite 450C-199 120 South Denton Tap Coppell, TX 75019 USA Tel: (972) 393-3603 Fax: (972) 393-9186 Santa Clara, CA 95054 USA Tel: (408) 914-7670 Fax: (408) 914-7878 Worldwide Web Literature Requests http://www.micrel.com USA: 1-800-401-9572 Outside the U.S.: Contact sales office HTTP:// www.micrel.com/analogsolutions.html