|Category||Power Management => DC-DC Converters => DC-DC Switching => Switching DC-DC Regulation|
|Title||Switching DC-DC Regulation|
|Description||up to 1A Step Down Switching Regulator|
|Company||ST Microelectronics, Inc.|
|Datasheet||Download L5970 datasheet|
TO 1A OUTPUT CURRENT OPERATING INPUT VOLTAGE FROM (±2%) / REFERENCE VOLTAGE OUTPUT VOLTAGE ADJUSTABLE FROM TO 35V LOW DROPOUT OPERATION: 100% DUTY CYCLE 250KHz INTERNALLY FIXED FREQUENCY VOLTAGE FEEDFORWARD ZERO LOAD CURRENT OPERATION INTERNAL CURRENT LIMITING INHIBIT FOR ZERO CURRENT CONSUMPTION SINCHRONIZATION PROTECTION AGAINST FEEDBACK DISCONNECTION THERMAL SHUTDOWN
DESCRIPTION The is a step down monolithic power switching regulator capable to deliver 1A at output voltages from to 35V. The device uses an internal P-Channel D-MOS transistor (with a typical Rdson 250m) as switching element to minimize the size of the external components. An internal oscillator fixes the switching frequency at 250KHz. Having a minimum input voltage of 4.4V only, it is particularly suitable for 5V bus, available in all computer related applications. Pulse by pulse current limit with the internal frequency modulation offers an effective constant current short circuit protection.
APPLICATIONS: s CONSUMER: STB, DVD, TV, VCR,CAR RADIO, LCD MONITORS s NETWORKING: XDSL, MODEMS,DC-DC MODULES s COMPUTER: PRINTERS, AUDIO/GRAPHIC CARDS, OPTICAL STORAGE, HARD DISK DRIVE s INDUSTRIAL: CHARGERS, CAR BATTERY DC-DC CONVERTERS TEST APPLICATION CIRCUIT
N. Name OUT SYNC INH COMP FB VREF GND VCC Regulator Output. Master/slave synchronization. A logical signal (active high) disables the device. If INH not used the pin must be grounded. When it is open an internal pull-up disable the device. E/A output for frequency compensation. Feedback input. Connecting directly to this pin results in an output voltage 1.23V. An external resistive divider is required for higher output voltages. 3.3V VREF. No cap is requested for stability. Ground. Unregulated DC input voltage. DescriptionRth (j-amb) Thermal Resistance Junction to ambient Max.
Symbol V3 V2 Ptot Tj Tstg Input Voltage Output DC voltage Output peak voltage = 0.1µs Maximum output current Analog pins INH SYNC Power dissipation at Tamb 60°C Operating junction temperature range Storage temperature range Parameter Value to 40 int. limit. -0.3V to VCC °C V Unit V
ELECTRICAL CHARACTERISTCS (Tj = 25°C, VCC = 12V, unless otherwise specified.) Specification Referred to Tj from +125°C (1).
Symbol VCC RDSON Il fs Parameter Operating input voltage range Mosfet on Resistance Maximum limiting current Switching frequency Duty cycle DYNAMIC CHARACTERISTICS (see test circuit). V5 Voltage feedback 4.4V < VCC < 1A Efficiency = 5V, VCC 12V * Duty Cycle = 0; VFB = 1.5V Vinh > 2.2V VCC = 36V; Vinh > 2.2V Device ON Device OFF VFB = 1V VFB = 1.5V VCOMP = 1.9V; VFB = 1V Vcomp = 1.9V; VFB RL = Icomp to 0.1mA Vcomp = 1.9V VCC to 36V VCC to 36V Vsync = 0.74V Vsync = 2.33V Isource 3mA no load, Vsync = 1.65V
DC CHARACTERISTICS Total operating quiescent Iqop current Quiescent current Iq Iqst-by INHIBIT INH Threshold voltage ERROR AMPLIFIER High level output voltage VOH VOL Io source Io sink Ib gm Low level output voltage Source output current Sink output current Source bias current DC open loop gain Transconductance Total stand-by quiescent current
SYNC FUNCTION High Input Voltage Low Input Voltage Slave Sink Current Master Output Amplitude Output Pulse Width REFERENCE SECTION Reference Voltage IREF to 5mA VCC to 36V Line Regulation Load Regulation Short Circuit Current IREF = 0mA VCC to 36V IREF to 5mA VREF mV mA
Note (1): Specification over the +125 Tj Temperature range are assured by design, characterization and statistical correlation. Note (2): Guaranteed by design.
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