A6902D Up to 1A step down switching regulator with adjustable current limit for automotive applications Features ■ Qualified following the AEC-Q100 requirements (temperature Grade 3), see PPAP for more details. ■ Temperature range -40°C to 85°C ■ Up to 1A DC output current ■ Operating input voltage from 8V to 36V Description ■ Output voltage adjustable from 1.235V to 35V ■ Precise 3.3V (±2%) reference voltage ■ 250kHz Internally fixed frequency ■ Voltage feedforward ■ Zero load current operation ■ Internal current limiting ■ Protection against feedback disconnection ■ Thermal shutdown The A6902D is a complete and simple step down switching regulator with adjustable current limit, capable to deliver up to 1A at output voltages from 1.2V to 35V. 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 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. SO-8 Applications ■ Dedicated to automotive applications ■ Adjustable current generator ■ Simple step-down converters with adjustable current limit Figure 1. Typical application VIN=8V to 36V VCC OUT VREF VIN=8V to 36V COMP D1 L6902D C1 10µF C2 35V 22nF C3 220pF CS+ CS- STPS340U Rsense VOUT=3.3V 100mO R1 5.6kO C4 100µF FB 10V R3 R2 GND 3.3kO 5.1kO November 2007 L1 22µH Rev 2 1/12 www.st.com 12 A6902D Contents Contents 1 Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 2.1 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.2 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 6 Order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2/12 A6902D 1 Device summary Device summary The A6902D is a complete and simple step down switching regulator with adjustable current limit. Based on a voltage mode structure it integrates a current 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 Cscompatible with GND too) a current limit programming is very simple and accurate. Moreover constant current control can be used to charge NiMH and NiCd batteries. 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. 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. 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. 3/12 A6902D Pin settings 2 Pin settings 2.1 Pin connection Figure 2. 2.2 Pin connection (top view) Pin description Table 1. Pin description N Pin Description 1 OUT Regulator 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 6 VREF 3.3V reference voltage. No cap is need for stability. 7 GND Ground. 8 VCC Unregulated DC input voltage. E/A output for frequency compensation. Feedback input. Connecting directly to this pin results in an output voltage of 1.23V. An extenal resistive divider is required for higher output voltages. 4/12 A6902D Electrical data 3 Electrical data 3.1 Maximum ratings Table 2. Absolute maximum ratings Symbol Value Unit 40 V V V V8 Input voltage V1 OUT pin DC voltage OUT pin peak voltage at ∆t=0.1µs -1 to 40 -5 to 40 I1 Maximum output current int. limit. V4 , V5 Analog pins 4 V V2, V3 Analog pins -0.3 to VCC V PTOT Power dissipation at TA ≤ 70°C 0.7 W Operating junction temperature range -40 to 150 °C Storage temperature range -55 to 150 °C SO-8 Unit 110 (1) °C/W Tj TSTG 3.2 Parameter Thermal data Table 3. Thermal data Symbol RthJA Parameter Maximum thermal resistance junction-ambient 1. Package mounted on board 5/12 A6902D 4 Electrical characteristics Electrical characteristics Table 4. Electrical characteristics (TJ=-40 to 85°C, VCC = 12V, unless otherwise specified) Symbol Parameter VCC Operating input voltage range RDS(on) Test condition V0=1.235V; I0=2A Min Maximum limiting current VCC=8.5V I0 Operating charging current Rsense=0.1Ω fSW Switching frequency 2 Unit 36 V 0.250 0.5 Ω 2.5 3.2 A 1.08 A 280 kHz 100 % 1.272 V 0.92 212 Duty cycle Max 8 Mosfet on resistance IL Typ 250 0 Dynamic characteristics (see test circuit). V5 Voltage feedback 8V<VCC<36V, 20mA<I0<1A η Efficiency V0=5V, VCC=12V 1.198 1.235 90 % DC characteristics Iqop Total operating quiescent current Iq Quiescent current 3 Duty cycle=0; VFB=1.5V 5 mA 2.7 mA Error amplifier VOH High level output voltage VFB=1V VOL Low level output voltage VFB=1.5V 3.6 V 0.4 V Source output current VCOMP = 1.9V; VFB = 1V 190 300 µA Io sink Sink output current VCOMP = 1.9V; VFB = 1.5V 1 1.5 mA Ib Source bias current Io source 2.5 DC open loop gain RL= ∞ gm Transconductance ICOMP = -0.1mA to 0.1mA; VCOMP = 1.9V VOFFS Input offset voltage VCS- = 1.8V; VCS+ = Vcomp ICS+ CS+ output current ICS- CS- output current 50 90 4 µA 58 dB 2.3 mS 100 110 mV I0 =1A; RSENSE =100mΩ; VOUT<VCC-2V 1.5 3 µA I0 =1A; RSENSE =100mΩ; VOUT<VCC-2V 1.5 3 µA 6/12 A6902D Electrical characteristics Table 4. Electrical characteristics (TJ=-40 to 85°C, VCC = 12V, unless otherwise specified) Symbol Parameter Test condition Min Typ Max Unit 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 18 35 mA Short circuit current 5 7/12 A6902D 5 Package mechanical data Package mechanical data In order to meet environmental requirements, ST offers these devices in ECOPACK® packages. These packages have a Lead-free second level interconnect . The category of second level interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com 8/12 A6902D Package mechanical data Table 5. SO-8 mechanical data 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 (1) 4.80 5.00 0.189 0.197 E 3.80 4.00 0.15 0.157 D 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 0° (min.), 8° (max.) ddd 0.10 0.004 1. Dimensions D does not include mold flash, protru-sions or gate burrs. Mold flash, potrusions or gate burrs shall not exceed 0.15mm (.006inch) in total (both side). Figure 3. Package dimensions 9/12 A6902D 6 Order codes Order codes Table 6. Order code Order code Package A6902D Packing Tube SO-8 A6902D13TR Tape and reel 10/12 A6902D 7 Revision history Revision history Table 7. Document revision history Date Revision Changes 02-Oct-2007 1 Initial release 5-Nov-2007 2 Updated: Table 4 on page 6 11/12 A6902D Please Read Carefully: Information in this document is provided solely in connection with ST products. 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