L6902D UP TO 1A SWITCHING REGULATOR WITH ADJUSTABLE CURRENT LIMIT ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ UP TO 1A OUTPUT CURRENT OPERATING INPUT VOLTAGE FROM 8V TO 36V PRECISE 3.3V (±2%) REFERENCE VOLTAGE 5% OUTPUT CURRENT ACCURACY OUTPUT VOLTAGE ADJUSTABLE FROM 1.235V TO 34V 250KHz INTERNALLY FIXED FREQUENCY VOLTAGE FEEDFORWARD ZERO LOAD CURRENT OPERATION ADJUSTABLE CURRENT LIMIT PROTECTION AGAINST FEEDBACK DISCONNECTION THERMAL SHUTDOWN SO8 ORDERING NUMBERS: L6902D L6902D013TR (Tape & Reel) rent error amplifier to have a constant voltage and constant current control. By means of an on board current sense resistor and the availability of the current sense pins (both compatible to Vcc and for Cs- compatible with GND too) a current limit programming is very simple and accurate (±5%). Moreover constant current control can be used to charge NiMH and NiCd batteries. APPLICATIONS ■ CHARGERS FOR NiCd, NiMH BATTERIES AND PREREGULATOR FOR LITHIUM-ION BATTERIES ■ ADJUSTABLE CURRENT GENERATOR ■ SIMPLE STEP-DOWN CONVERTERS WITH ADJUSTABLE CURRENT LIMIT ■ BATTERY EQUIPPED SYSTEMS ■ DISTRIBUTED POWER SUPPLY ■ MOBILE PC & SUBNOTEBOOK The device can be used as a standard DC/DC converter with adjustable current limit (set by using the external sense resistor). The internal robust P-Channel DMOS transistor with a typical of 250mΩ assures high efficiency and a minimum dropout even at high output current level. The internal limiting current (latched function) of typical value of 2.5A protects the device from accidental output short circuit avoiding dangerous loads damage. DESCRIPTION If the temperature of the chip goes higher than a fixed internal threshold (150°C with 20°C hysteresis), the power stage is turned off. The L6902D is a complete and simple step down switching regulator with adjustable current limit. Based on a voltage mode structure it integrates a curTEST AND APPLICATION CIRCUIT VIN=8V to 36V VCC 3.3V VREF COMP C1 10µF 25V CERAMIC C3 220pF 1 8 6 2 4 L1 22µH RSENSE D1 STPS340U 100mΩ VOUT=3.3V R1 5.6K 3 C2 22nF R3 5.1K OUT 7 GND 5 FB R2 3.3K C4 100µF 10V POSCAP D01IN1306A June 2002 1/6 L6902D DESCRIPTION (Continued) Other protections beside thermal shutdown complete the device for a safe and reliable application: overvoltage protection, frequency folback overcurrent protection and protection vs. feedback disconnection. The internal fixed switching frequency of 250KHz, and the SO-8 package pin allow to built an ultra compact DC/ DC converter with a minimum board space. PIN CONNECTION OUT 1 8 VCC CS+ 2 7 GND CS- 3 6 VREF COMP 4 5 FB PIN DESCRIPTION N° Pin Function 1 OUT Regular Output 2 CS+ Current Error Amplifier input (current sense at higher voltage) 3 CS- Current Error Amplifier input (current sense at lower voltage) 4 COMP 5 FB E/A output to be used for frequency compensation Stepdown feedback input. Connecting directly to this pin results in an output voltage of 1.235V. An external resistive divider is required for higher output voltages. In this case: R1 R1 V out = V F B ⋅ 1 + -------- = 1.235V 1 + -------- R2 R 2 6 VREF 7 GND Ground 8 VCC Unregulated DC input voltage. 3.3V VREF. No cap is need for stability. THERMAL DATA Symbol Rth j-amb Parameter Thermal Resistance Junction to Ambient Max. Value Unit 110 (*) °C/W Value Unit 40 V -1 to 40 -5 to 40 V V (*) Package mounted on board. ABSOLUTE MAXIMUM RATINGS Symbol Input Voltage V1 Output DC voltageOutput peak voltage at t = 0.1µs I1 Maximum output current Internally limited V4, V5 Analog pins 4 V V2, V3 Analog pins -0.3V to VCC V Ptot Tj Tstg 2/6 Parameter V8 Power dissipation at Tamb ≤ 70 °C 0.7 W Operating junction temperature range -40 to 150 °C Storage temperature range -55 to 150 °C L6902D INTERNAL BLOCK DIAGRAM Vcc VOLTAGES MONITOR 3.8V INHIBIT 1.235V CS+ VREF GOOD SUPPLY Vref Current_E/A + THERMAL SHUTDOWN - TRIMMING CS- COMP PEAK TO PEAK CURRENT LIMITING Voltage_E/A VFB 1.235V + E/A - - D PWM Q + DRIVER CK OSCILLATOR OUT FREQUENCY SHIFTER GND ELECTRICAL CHARACTERISTCS (Tj = 25°C, VCC = 12V, unless otherwise specified.) (•) Specification Referred to Tj from 0 to 125°C. Symbol VCC Parameter Test Condition Min. Operating input voltage range VO = 1.235V; IO = 1A • Vd Dropout voltage VCC = 8V; IO = 1A • IO Operating charging current Rsense = 0.1Ω Il Maximum limiting current fs Switching frequency d VCC = 8V to 36V Typ. Max. Unit 36 V 0.25 0.5 V 1 1.05 A 1.08 A 8 0.95 • 0.92 • 2 2.5 3.2 A • 212 250 287 kHz 225 250 275 kHz 100 % Duty cycle 0 DYNAMIC CHARACTERISTICS V5 η Voltage feedback (FB) Efficiency 8V < VCC < 36V, 20mA < IO < 1A • VO = 5V, VCC = 12V 1.21 1.235 1.259 V 1.198 1.235 1.272 V 90 % DC CHARACTERISTICS Iqop Iq Total operating quiescent current Quiescent current • Duty cycle = 0; VFB = 1.5V 3 5 mA 2.7 mA 3/6 L6902D ELECTRICAL CHARACTERISTCS (continued) (Tj = 25°C, VCC = 12V, unless otherwise specified.) (•) Specification Referred to Tj from 0 to 125°C. Symbol Parameter Test Condition Min. Typ. Max. Unit VOLTAGE ERROR AMPLIFIER VOH High level output voltage VFB = 1V VOL Low level output voltage VFB = 1.5 Source output current Vcomp = 1.9V; VFB = 1V Io sink Sink output current Vcomp = 1.9V; VFB = 1.5V Ib Source bias current Io source gm 3.6 V 0.4 200 300 µA 1 1.5 mA 2.5 DC open loop gain RL = 0 Transconductance Icomp = -0.1 to 0.1mA Vcomp = 1.9V V 50 4 µA 58 dB 2.3 mS CURRENT ERROR AMPLIFIER Voffs Input offset voltage VCS- = 1.8V; VCS+ = Vcomp ICS+ CS+ Output Current ICS- CS- Output Current 90 100 110 mV IO = 1A, Rsense = 100mΩ Vout < VCC -2V 1.5 3 µA IO = 1A, Rsense = 100mΩ Vout < VCC -2V 1.5 3 µA 3.234 3.3 3.366 V 3.2 3.3 3.399 V REFERENCE SECTION Reference Voltage IREF = 0 to 5mA VCC = 8V to 36V Line Regulation IREF = 0mA VCC = 8V to 36V 5 10 mV Load Regulation IREF = 0 to 5mA 8 15 mV Short Circuit Current 4/6 • 10 mA L6902D mm DIM. MIN. TYP. A a1 inch MAX. MIN. TYP. 1.75 0.1 0.25 a2 MAX. 0.069 0.004 0.010 1.65 0.065 a3 0.65 0.85 0.026 0.033 b 0.35 0.48 0.014 0.019 b1 0.19 0.25 0.007 0.010 C 0.25 0.5 0.010 0.020 c1 45° (typ.) D (1) 4.8 5.0 0.189 0.197 E 5.8 6.2 0.228 0.244 e 1.27 0.050 e3 3.81 0.150 F (1) 3.8 4.0 0.15 0.157 L 0.4 1.27 0.016 0.050 M S OUTLINE AND MECHANICAL DATA 0.6 0.024 SO8 8 ° (max.) (1) D and F do not include mold flash or protrusions. Mold flash or potrusions shall not exceed 0.15mm (.006inch). 5/6 L6902D Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. The ST logo is a registered trademark of STMicroelectronics © 2002 STMicroelectronics - All Rights Reserved STMicroelectronics GROUP OF COMPANIES Australia - Brazil - Canada - China - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan -Malaysia - Malta - Morocco Singapore - Spain - Sweden - Switzerland - United Kingdom - United States. http://www.st.com 6/6