ML4854

www.fairchildsemi.com ML4854 Adjustable, Low-Current, 2-Cell Boost Regulator with Shutdown and Low Battery Detect Features • • • • • 95% Efficiency at 200mA Load Current Integrated Peak Current Limit Variable Output Voltage Determined by External Resistors Variable On-time Pulse Frequency Modulation (PFM) Fully Internal Synchronous Rectifier (no external diodes) for High Efficiency and Low Peak Currents • Low-Battery Detection • Logic Controlled Shutdown with True Load Disconnect General Description The ML4854 is a low power boost regulator designed for low voltage DC to DC conversion in two-cell battery powered systems such as cell phones and PDAs. The converter starts up at 1.3V and has an operating input voltage range from 1.6V to 4.5V. After the start it operates at an input voltage as low as 0.8V. Output voltage can be adjusted by external resistors from 3.3V to 5V with a maximum load current of 0.5A. Quiescent current in shut down mode is less than 30µA, which maximizes the battery live time. The ON time changes with the input voltage to maintain the ripple current constant and to provide the highest efficiency over a wide load range, while maintaining low peak currents in the boost inductor. The combination of integrated synchronous rectification, variable frequency operation, and low supply current make ML4854 ideal for portable applications. The ML4854 is available in an 8 lead TSSOP package. Applications • • • • • 2-3 alkaline/NiMH cells or 1 Li-Ion cell Operated Devices Cell Phones Medical Devices PDAs Portable Instrumentation Typical Application Input 1.6V to 4.5V ML4854 On Off Low Battery Detect In Low Battery Detect Out 1 VIN 2 SHDN 3 LBI 4 LB0 GND 8 VL 7 VOUT 6 FB 5 Output 3.3V to 5V up to 0.5A REV. 1.0.7 5/6/03 PRODUCT SPECIFICATION ML4854 Pin Configuration 8-Lead TSSOP (T08) VIN SHDN LBI LB0 1 2 3 4 TOP VIEW 8 7 6 5 GND VL VOUT FB Pin Description PIN 1 2 3 4 NAME VIN SHDN LBI LBO FUNCTION Battery Input Voltage. Supplies the IC during start-up. After the output is running, the IC draws power from VOUT. Shut Down. Pulling this pin low shuts down the regulator, isolating the load from the input. Low-Battery Input. Pulling this pin below a threshold causes the LBO pin to go low. Low-Battery Output. This pin provides an active low signal to alert the user when the LBI voltage falls below its targeted value. The open-drain output can be used to reset a microcontroller. Programming Feedback Pin. Sets the output voltage. This pin is used to adjust the output voltage via a resistive divider from VOUT. Boost regulator output. Output voltage can be set to be in the 3 to 5V range. Startup at moderate load is achievable at input voltages around 1.25V. Boost inductor connection. An inductor is connected between this pin and VIN. When servicing the output supply, this pin pulls low, charging the inductor, then shuts off dumping the energy through the synchronous rectifier to the output. Ground of the IC. 5 6 7 FB VOUT VL 8 GND Absolute Maximum Ratings Absolute maximum ratings are those values, beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied. Parameter VIN, VOUT Voltages (Relative to GND) Switch Voltage (VL to GND) Voltage on any other Pin Peak Switch Current (Ipeak) Output Current (IOUT) Continuous Power Dissipation Thermal Resistance (θJA) Junction Temperature Storage Temperature Range Lead Temperature (soldering, 10s) -65 Min. -0.3 -0.3 -0.3 Max. 7 VOUT+0.3 VOUT+0.3 — Internally Limited — 500 320 124 150 +165 300 mA mW °C/W °C °C °C Units V V V 2 REV. 1.0.7 5/6/03 ML4854 PRODUCT SPECIFICATION Recommended Operating Conditions Parameter Temperature Range VIN Operating Range VOUT Operating Range Min. -40 1.6 3.0 Max. +85 0.9 VOUT 5.0 Units °C V V Electrical Characteristics Unless otherwise specified, VIN=1.6V to 3V, ILOAD=1mA, TA=-40°C to +85°C. Test Circuit Fig.1. Typical values are at TA= +25°C Parameter Start Up Voltage Operating Voltage Output Voltage Output Voltage Adjust Range Steady State Output Current (see diagram) Pulse Width VOUT=3.3V, VIN=2.5V VOUT=5V, VIN=2.5V VIN = 3V VIN = 2.4V VIN = 1.8V VIN = 1.5V Minimum Off-Time Line Regulation Load Regulation Feedback Voltage (VFB) LBI Threshold Voltage LBI Hysteresys Internal NFET, PFET ON Resist. Efficiency Quiescent Current – SHDN LBO Output Voltage SHDN Input Voltage @VIN=3V SHDN Input Voltage @VIN=1.6V ILOAD = 100mA (ILOAD=200mA) VIN=3V, VOUT = 3.3V SHDN=0V, R1 excluded,VIN=3V SHDN=3V, R1 excluded,VIN=3V VLBI= 0, ISINK=1mA VOUT=3.3V/5V VOUT=3.3V/5V VIN=1.6V to 3V, IOUT=2mA, VOUT=3.3V VOUT=5V 0 to 250mA VIN=2.4V ,VOUT=3.3V 0 to 150mA VIN=2.4V ,VOUT=5V 0.8 1.2 1.8 2.2 ILOAD 0.5µS, determined by Minimum Off–Time Logic and if VOUT is low (VFB 50 mils or 1.25 mm. Place the external networks for LBI and FB close to ML4854, but as far away as possible from the power components to prevent voltage transient from coupling into sensitive nodes. 5. On multilayer boards, use component side copper for grounding around the IC and connect back to a quiet ground plane using vias. The ground planes act as electrostatic shields for some of the RF energy radiated. The connection of the GND pin of the IC (pin 8) to the overall grounding system should be directly to the bottom of the output filter capacitor. A star grounding system radiating from where the power enters the PCB, is a recommended practice. 6. 3. 4. Application Example: Using ML4854 as a constant current source to drive four LEDs: L ML4854 1 2 3 4 8 7 6 5 D1 R D2 R L = 10µH Cin = Cout = 10µF R = 62 ohm D1...D4 = QTLP 600C-EB (blue) Cin + + + D3 Cout D4 R R The current through the LEDs is maintained constant within a large input voltage range as shown in the diagram below: ML4854 feeds LED QTLP 600C-EB 20 19.8 19.6 19.4 19.2 19 18.8 18.6 18.4 18.2 18 0 1 2 3 4 5 Input Voltage (V) LED Current (mA) REV. 1.0.7 5/6/03 11 PRODUCT SPECIFICATION ML4854 Mechanical Dimensions Package: T08 8-Lead TSSOP 0.113 - 0.123 (2.87 - 3.12) 8 0.169 - 0.177 0.246 - 0.258 (4.29 - 4.50) (6.25 - 6.55) PIN 1 ID 1 0.026 BSC (0.65 BSC) 0.043 MAX (1.10 MAX) 0°-8° 0.033 - 0.037 (0.84 - 0.94) 0.008 - 0.012 (0.20 - 0.30) 0.002 - 0.006 (0.05 - 0.71) 0.020 - 0.028 (0.51 - 0.71) 0.004 - 0.008 (0.10 - 0.20) SEATING PLANE 12 REV. 1.0.7 5/6/03 PRODUCT SPECIFICATION ML4854 Ordering Information Part Number ML4854IT Temperature Range –40°C to 85°C Package 8 Pin TSSOP (T08) DISCLAIMER FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS. LIFE SUPPORT POLICY FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury of the user. 2. A critical component in any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. www.fairchildsemi.com 5/6/03 0.0m 004 Stock#DS30004854  2003 Fairchild Semiconductor Corporation