L6902D UP TO 1A SWITCHING REGULATOR WITH ADJUSTABLE CURRENT LIMIT 1 ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ 2 ■ ■ ■ ■ ■ ■ 3 Figure 1. Package FEATURES 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 SO-8 Table 1. Order Codes Part Number Package L6902D SO-8 L6902D013TR SO-8 in 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 The L6902D is a complete and simple step down switching regulator with adjustable current limit. Based on a voltage mode structure it integrates a cur- 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. Figure 2. Test And Application Circuit VCC VIN=8V to 36V 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 October 2004 Rev. 8 1/7 L6902D 3 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. Figure 3. Pin Connection OUT 1 8 VCC CS+ 2 7 GND CS- 3 6 VREF COMP 4 5 FB Table 2. Pin Description N° Pin 1 OUT Function 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 Regular Output 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: V out = V FB ⋅ 1 + R1 -------- = 1.235V 1 + R1 -------- R2 R2 6 VREF 3.3V VREF. No cap is need for stability. 7 GND Ground 8 VCC Unregulated DC input voltage. Table 3. Thermal Data Symbol Rth j-amb Parameter Thermal Resistance Junction to Ambient Max. Value Unit 110 (*) °C/W Value Unit (*) Package mounted on board. Table 4. Absolute Maximum Ratings Symbol V8 Input Voltage V1 Output DC voltageOutput peak voltage at t = 0.1µs I1 Maximum output current 40 V -1 to 40 -5 to 40 V V Internally limited V4, V5 Analog pins 4 V V2, V3 Analog pins -0.3V to VCC V 0.7 W Ptot Tj Tstg 2/7 Parameter Power dissipation at Tamb ≤ 70 °C Operating junction temperature range -40 to 150 °C Storage temperature range -55 to 150 °C L6902D Figure 4. Internal Block Diagram Vcc VOLTAGES MONITOR 3.8V INHIBIT 1.235V CS+ VREF GOOD SUPPLY Vref Current_E/A + THERMAL SHUTDOWN - TRIMMING CSCOMP PEAK TO PEAK CURRENT LIMITING Voltage_E/A VFB 1.235V + E/A - - D PWM Q + DRIVER CK OSCILLATOR OUT FREQUENCY SHIFTER GND Table 5. Electrical Characteristcs (Tj = 25°C, VCC = 12V, unless otherwise specified.) (•) Specification Referred to Tj from 0 to 125°C. Symbol 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 VCC 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 3 mA 3/7 L6902D Table 5. 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 95 100 105 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 4/7 • 10 mA L6902D Figure 5. SO-8 Mechanical Data & Package Dimensions mm inch DIM. MIN. TYP. MAX. MIN. TYP. MAX. A 1.35 1.75 0.053 0.069 A1 0.10 0.25 0.004 0.010 A2 1.10 1.65 0.043 0.065 B 0.33 0.51 0.013 0.020 C 0.19 0.25 0.007 0.010 D (1) 4.80 5.00 0.189 0.197 E 3.80 4.00 0.15 0.157 e 1.27 0.050 H 5.80 6.20 0.228 0.244 h 0.25 0.50 0.010 0.020 L 0.40 1.27 0.016 0.050 k ddd OUTLINE AND MECHANICAL DATA 0˚ (min.), 8˚ (max.) 0.10 0.004 Note: (1) Dimensions D does not include mold flash, protrusions or gate burrs. Mold flash, potrusions or gate burrs shall not exceed 0.15mm (.006inch) in total (both side). SO-8 0016023 C 5/7 L6902D Table 6. Revision History 6/7 Date Revision Description of Changes January 2004 7 Technical Migration from ST-PRESS to EDOCS. October 2004 8 Changed Style Look & Feel. Changed Iq value in Table 5 page 3/7 from 2.7mA max. to 3.0mA max. 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. 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