L5970AD 1.5A SWITCH STEP DOWN SWITCHING REGULATOR 1 General Features Figure 1. Package 1.5A INTERNAL SWITCH OPERATING INPUT VOLTAGE FROM 4.4V TO 36V 3.3V / (2%) REFERENCE VOLTAGE OUTPUT VOLTAGE ADJUSTABLE FROM SO-8 1.235V TO 35V LOW DROPOUT OPERATION: 100% DUTY Table 1. Order Codes CYCLE Part Number Package 500KHz INTERNALLY FIXED FREQUENCY L5970AD SO-8 VOLTAGE FEEDFORWARD L5970ADTR SO-8 in Tape & Reel ZERO LOAD CURRENT OPERATION INTERNAL CURRENT LIMITING 2 Description INHIBIT FOR ZERO CURRENT CONSUMPTION The L5970AD is a step down monolithic power SYNCHRONIZATION switching regulator with a switch current limit of 1.5A so it is able to deliver more than 1A DC current to the PROTECTION AGAINST FEEDBACK load depending on the application conditions. DISCONNECTION The output voltage can be set from 1.235V to 35V. THERMAL SHUTDOWN The device uses an internal P-Channel D-MOS tran- 1.1 APPLICATIONS: sistor (with a typical R of 200m ) as switching DSON CONSUMER: STB, DVD, TV, VCR,CAR element to avoid the use of bootstrap capacitor and RADIO, LCD MONITORS guarantee high efficiency. NETWORKING: XDSL, MODEMS,DC-DC An internal oscillator fixes the switching frequency at MODULES 500KHz to minimize the size of external components. COMPUTER: PRINTERS, AUDIO/GRAPHIC Having a minimum input voltage of 4.4V only, it is CARDS, OPTICAL STORAGE, HARD DISK particularly suitable for 5V bus, available in all com- DRIVE puter related applications. INDUSTRIAL: CHARGERS, CAR BATTERY Pulse by pulse current limit with the internal frequen- DC-DC CONVERTERS cy modulation offers an effective constant current short circuit protection. Figure 2. Test and Application Circuit VREF L1 15H 3.3V VOUT=3.3V 6 OUT 1 VIN = 4.4V to 35V VCC D1 8 R1 L5970AD STPS2L25U SYNC. 2 5.6K C2 5 COMP 330F 3 7 C1 4 FB 10V C4 10F INH GND 22nF 35V R2 CERAMIC 3.3K C3 R3 220pF 4.7K D05IN1530 Rev. 1 March 2005 1/11L5970AD Table 2. Thermal Data Symbol Parameter Value Unit R Thermal Resistance Junction to ambient Max. 120 (*) C/W th (j-amb) (*) Package mounted on board Figure 3. Pin Connection (top view) OUT 1 8 VCC SYNC 2 7 GND INH 3 6 VREF COMP 4 5 FB D98IN955 Table 3. Pin Description N. Name Description 1 OUT Regulator Output. 2 SYNC Master/Slave Synchronization. When it is open, a signal synchronous with the turn-off of the inter- nal power is present at the pin. When connected to an external signal at a frequency higher than the internal one, then the device is synchronized by the external signal. Connecting together the SYNC pin of two devices, the one with the higher frequency works as master and the other one, works as slave. 3INH A logical signal (active high) disables the device. With IHN higher than 2.2V the device is OFF and with INH lower than 0.8V, the device is ON. If INH is not used the pin must be grounded. When it is open, an internal pull-up disables the device. 4 COMP E/A output to be used for frequency compensation. 5 FB Stepdown feedback input. Connecting the output voltage directly to this pin results in an output voltage of 1.235V. An external resistor divider is required for higher output voltages (the typical value for the resistor connected between this pin and ground is 4.7K). 6V Reference voltage of 3.3V. No filter capacitor is needed to stability. REF 7 GND Ground. 8V Unregulated DC input voltage. CC Table 4. Absolute Maximum Ratings Symbol Parameter Value Unit V Input Voltage 40 V 8 Output DC voltage -1 to 40 V V 1 Output peak voltage at t = 0.1s -5 to 40 V I Maximum output current int. limit. 1 V , V Analog pins 4 V 4 5 V INH -0.3V to V 3 CC V SYNC -0.3 to 4 V 2 P Power dissipation at T 60C 0.75 W tot amb T Operating junction temperature range -40 to 150 C j T Storage temperature range -55 to 150 C stg 2/11