MP1521 MPS | Alldatasheet
Document overview
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Technical content
Features
On Board Power MOSFET Drive 9 White LEDs from 2.7V Input Drive 15 White LEDs from 5V Input Up to 90% Efficiency Over 80mA Output Current Capacity Open Load Shutdown Low Current Sensing Feedback Voltage Up to 3 String Current Sensing Feedback Analog and Digital PWM Brightness Control UVLO, Thermal Shutdown Soft Start Internal Current Limit Available in Compact MSOP10 and Tiny 3 mm x 3 mm QFN16 Package Evaluation Boards Available
Applications
Handheld Computers, Cell phones, PDAs, Digital and Video Cameras, Small LCD Displays Li Ion and NiMH Battery Applications Typical Application Circuit (One String of Six (6) LEDs) IN BRT/PWM FB1 OLS SW 10 GND 9 CIN COUT EN REF MP1521 6 5 FB2 FB3 White LEDs BRT/ PWM EN GND OFF ON VIN Efficiency vs LED current, 1 string of 6 Using Toko D62CB 47µH Inductor 100 5 10 15 20 25 LED Current (mA) Efficiency (%) VIN = 5V VIN = 4V VIN = 3V
MP1521 Rev 2.7 10/06/04 www.monolithicpower.com 2 Monolithic Power Systems Absolute Maximum Ratings Supply Voltage (VIN) 28V Switch Voltage to GND -0.5V to 28V V EN, VREF, VBRT, VFB1, VFB2, VFB3 –0.3V to 6V Storage Temperature -55 °C to +150°C Recommended Operating Conditions Supply Voltage (VIN) 2.7V to 25V Operating Temperature -20 °C to +85°C Switch Voltage to GND -0.5V to 25V Package Thermal Characteristics Thermal Resistance, ΘJA (MSOP10) 150°C/W Thermal Resistance, ΘJA (QFN16) 60°C/W Electrical Characteristics (VIN = 5.0V, TA = 25°C unless specified otherwise) Parameters Symbol Condition Min Typ Max Units Supply Current (shutdown) I IN (OFF) V EN<0.4V 1 3 µA Supply Current (quiescent) I IN (ON) V EN >1.5V, VBRT=0V, VFB=0V 550 700 µA Minimum Off Time, normal operation tOFF (NORMAL) VEN >1.5V, VBRT =0.6V VFB =0 400 500 700 nS Minimum Off Time, start-up (Note 1) tOFF (START) VEN >1.5V, VBRT =0.6V, VFB =0V 1.5 2.4 µS UVLO V IN RISING 2.1 2.6 V Under Voltage Lockout V IN FALLING 1.9 2.4 V Enable Threshold 0.8 1.0 2.0 V Hysterisis 60 mV Leakage Current V EN=3V 1 µA Open Load Shutdown Threshold Measured at OLS Pin 26 29 V VOLS=15V 1 µA Leakage Current VOLS=25V 45 70 µA Reference Output Voltage I REF=0A 1.20 1.235 1.27 V Load Regulation IREF=0 to 100µA 2.5 5 mV Line Regulation V IN =3 to 15V, IREF=0A 2.5 5 mV Feedback Comparator Threshold V BRT =1.2V 380 400 420 mV Hysterisis (Note 2) V BRT =1.2V 30 mV FB Input Bias Current V FB=0.2V -150 -50 0 nA PWM Mode Output-Off Threshold 0.18 0.26 V BRT Input Bias V BRT=0.6V -100 -30 0 nA BRT Full Scale Threshold (Note 3) 1.2 V Output Switch Switch On Resistance (Note 2) R ON V IN=5.0V 0.5 0.6 Ω Switch Current Limit 300 400 mA Leakage Current V SW=25V 5 µA Thermal Shutdown (Note 2) 160 °C Notes: 1) First 64 pulses after EN switches high. 2) Guaranteed by design. 3) The output current is off when BRT is driven below the output-off threshold and full-scale when driven above the full-scale threshold. To PWM the output drive BRT above and below these thresholds.
MP1521 Rev 2.7 10/06/04 www.monolithicpower.com 3 Monolithic Power Systems Pin Description MSOP10 QFN16 Part Marking: MP1521EK Part Marking: A1xx Table 1: MP1521 MSOP10 and QFN16 Pin Assignments MSOP Pin # QFN Pin# Pin Name Pin Function 1 16 IN Input supply pin. It can be connected to the regulator’s input supply, or to the output for boot-strapped operation (boot- strapped operation is required for V IN of less than 3V). 2 2 EN Regulator On/Off control input. Logic high (V EN>1V) turns on IC, logic low puts it into low current shutdown mode. Place a 100K Ω resistor in series with EN if it is connected to a voltage greater than 10V. 3 4 REF 1.23V reference used for setting the analog control voltage at BRT input. This reference can supply up to 200 µA to an external load. Do not connect any bypass capacitors to this pin. It is internally compensated. 4 5 BRT Analog or PWM input for co ntrolling LED bright ness. When us ed in analog mode, apply a DC voltage of 0.3 to 1.2V. This input voltage is attenuated by 1/3 to set the voltage across sense resist ors at FB1, FB2, and FB3. Maximum brightness (20mA) occurs with 1.2V a pplied. To control brightness in PWM mode, apply a PWM square wave with a minimum voltage less the 0.18V and a maximum greater than 1.2V. When a voltage less than 0.18V is applied to this pin, the output switch is turned o ff. The regulator operates at maximum brightness when more than 1.2V is app lied. The frequency of the PWM signal must be between 100 to 400 Hz. FB3 FB2 FB1 Feedback input for measuring voltage across current-sense resistor that is in series with LED string. Unused feedb ack pins must be connected to any used feedback pin. 8 10 OLS Open Load Shutdown pin senses regulato r output voltage to protect IC during open load operation. When this pin’s voltage exceeds 28V, the output switch is shut off. The output switch remains off unt il the IC is reset by cycling the enable pin (EN) or input supply (IN) pin. 9 11, 12 GND Signal and power ground. Connect directly to ground plane. 10 14 SW Output switch pin, power DMOS low-side switch. - 1, 3, 6, 13, 15 N/C No Connect SW GND OLS FB1 FB2 IN EN REF BRT FB3 NC EN NC REF Top View GND GND OLS FB1 BRT NC FB3 FB2 IN NC SW NC
MP1521 Rev 2.7 10/06/04 www.monolithicpower.com 4 Monolithic Power Systems Figure 2: MP1521 Functional Block Diagram Internal Regulator & Enable Circuit UVLO & Th e r m a l Shutdown Control Logic & Output Driv er - GND 500nS One-Shot Ti m e r SW EN IN Open Load Shutdown Comparator 1.23V 160K 17V 20K 0.25V Current Limit Comparator 0.5 W Power FET - FB1 Feedback Comparator - 10K20K 1.2V - FB2 - FB3 OLS REF Bandgap Reference 1.23V BRT
MP1521 Rev 2.7 10/06/04 www.monolithicpower.com 5 Monolithic Power Systems Functional Description Operation The MP1521 utilizes a constant off-time control scheme (Refer to the Block Diagram). For maximum brightness, the BRT pin is biased at or above 1.2V. Its voltage is routed through the unity gain buffer whose the output of is clamped at 1.2V. A 20K/10K divider from the Buffer to the non-inverting input of the Feedback comparator divides the BRT voltage by three to set the current sense threshold. If any of the feedback pins FB1, FB2, or FB3 is lower than this threshold the Power FET is turned on. The Power MOSFET and inductor current increases until the current limit comparator trips at 0.5A turning off the MOSFET for 500ns. At the end of 500ns if any of the Feedback pins are still lower than the current sense threshold. The Power FET is again turned on. This cycle repeats itself until all three of the feedback pins exceed the threshold. Analog Brightness Adjust Analog Brightness Adjust is accomplished by applying a voltage between 0.26V to 1.2V on the BRT pin. The 1.23V REF output can be used to bias a potentiometer whose wiper drives the BRT pin. PWM/ Brightness Adjust PWM Brightness Adjust is accomplished by driving the BRT pin with a square wave whose low voltage is below 0.2V and whose high voltage is greater than 1.2V. A voltage below 0.2V forces the Power MOSFET off. A voltage greater than 1.2V will cause all three feedback pins to regulate at or above 0.4V Open Load Shut-Off Open Load Shut-Off is implemented by connecting the OLS pin to V OUT. In the fault condition where the connection to the LED’s is open, V OUT will rise up, as all the feedback pins are absent of voltage. Once V OUT exceeds 28V, the part will cease operation until the EN pin is cycled off and on. To disable the open load shut-off feature, connect the OLS pin to GND.
MP1521 Rev 2.7 Monolithic Power Systems, Inc. 8 10/06/04 983 University Ave, Building A, Los Gatos, CA 95032 USA © 2004 MPS, Inc. Tel: 408-357-6600 ♦ Fax: 408-357-6601 ♦ www.monolithicpower.com Monolithic Power Systems
Package Information
NOTE: 1) Control dimension is in inches. Dimension in bracket is millimeters. SEE DETAIL "A" 0.004(0.100) 0.008(0.200) GATE PLANE 0.010(0.250) 0.017(0.400) 0.025(0.600) 0o-6o DETAIL "A" 0.014(0.350)TYP 0.014(0.350)TYP 0.114(2.900) 0.122(3.100) 0.032(0.800) 0.044(1.100) 0.008(0.200)REF 0.030(0.750) 0.038(0.950) 0.002(0.050) 0.006(0.150) 0.0197(0.500)TYP PIN 1 IDENT 0.114(2.900) 0.122(3.100) 0.184(4.700) 0.200(5.100) QFN16 (3 x 3) 3.00 (0.118) BSC 0.18 (0.007) 0.28 (0.011) 0.550 (0.0217) 0.450 (0.0177) 1.400 (0.055) 1.700 (0.067) exp. pad NOTE: 1) Control dimension is in millimeters. Dimension in bracket is inch. 3.00 (0.118) BSC Pin 1 Identification 0.178 (0.007) 0.228 (0.009) 0.90 (0.035) 1.00 (0.039) 0.00 (0.000) 0.05 (0.002) Pin 1 Identification 1.500 (0.059) Ref. 1 4 912 Bottom View 0.450 (0.0177) 0.350 (0.0138) NOTICE: MPS believes the information in this document to be accurate and reliable. However, it is subject to change without notice. Please contact the factory for current specifications. No responsibility is assumed by MPS for its use or fit to any application, nor for infringement of patent or other rights of third parties.