B5973D

B5973D 2 A step down switching regulator for automotive applications Features ■ Qualified following the AEC-Q100 requirements (temperature Grade 1), see PPAP for more details. Temperature range -40 °C to +125 °C 2 A DC output current Operating input voltage from 4 V to 36 V 3.3 V / (±2 %) reference voltage Output voltage adjustable from 1.235 V to 35 V Low dropout operation: 100 % duty cycle 250 kHz internally fixed frequency Voltage feedforward Zero load current operation Internal current limiting Inhibit for zero current consumption Synchronization Protection against feedback disconnection Thermal shutdown HSOP8 exposed pad ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Description The B5973D is a step down monolithic power switching regulator with a minimum switch current limit of 2.25 A so it is able to deliver up to 2 A DC current to the load depending on the application conditions. The output voltage can be set from 1.235 V to 35 V. The high current level is also achieved thanks to an SO8 package with exposed frame, that allows to reduce the Rth(JA) down to approximately 40 °C/W. The device uses an internal P-channel DMOS transistor (with a typical RDSon of 250 mΩ) as switching element to minimize the size of the external components. An internal oscillator fixes the switching frequency at 250 kHz. Having a minimum input voltage of 4V only, it is particularly suitable for 5 V bus. Pulse by pulse current limit with the internal frequency modulation offers an effective constant current short circuit protection. Pulse by pulse current limit with the internal frequency modulation offers an effective constant current short circuit protection. L1 15uH Applications ■ Dedicated to automotive applications Figure 1. Typical application OUT O UT SYNCH 4 2 Vout=3.3V VIN=4V to 35V VCC COMP C4 C1 10uF 35V CERAMIC C3 220pF R3 4k7 22nF 8 1 B A5973D FB 6 5 7 GND INH 3 D1 STPS340U R1 5k6 C2 330uF 6.3V R2 3k3 VREF 3.3V January 2008 Rev 2 1/11 www.st.com 1 B5973D Contents Contents 1 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1 1.2 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2 Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1 2.2 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3 4 5 6 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1/11 B5973D 1 1.1 Pin settings Pin connection Figure 2. Pin connection (top view) 1.2 Pin description Table 1. N 1 2 3 4 5 6 7 8 Pin description Pin OUT SYNCH 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 of 1.23 V. An extenal resistive divider is required for higher output voltages. 3.3 V VREF. No cap is requested for stability. Ground. Unregulated DC input voltage. Description 2/11 Electrical data B5973D 2 2.1 Electrical data Maximum ratings Table 2. Symbol V8 V1 I1 V4 , V5 V3 V2 PTOT Tj TSTG Input voltage OUT pin DC voltage OUT pin peak voltage at ∆t = 0.1µs Maximum output current Analog pins INH SYNCH Power dissipation at TA ≤ 70 °C Operating junction temperature range Storage temperature range Absolute maximum ratings Parameter Value 40 -1 to 40 -5 to 40 int. limit. 4 -0.3 to VCC -0.3 to 4 2.25 -40 to 150 -55 to 150 V V V W °C °C Unit V V V 2.2 Thermal data Table 3. Symbol RthJA Thermal data Parameter Maximum thermal resistance junction-ambient SO8 40 (1) Unit °C/W 1. Package mounted on board 3/11 B5973D 3 Electrical characteristics Table 4. Symbol VCC RDS(on) IL fSW Electrical characteristics (TJ=-40 °C to 125 °C, VCC = 12 V, unless otherwise specified) Parameter Operating input voltage range MOSFET on resistance Maximum limiting current Switching frequency Duty cycle VCC=5 V 2.25 212 0 Test condition V0=1.235 V; I0=2 A Min 4 0.250 3 250 Typ Max 36 0.5 3.5 280 100 Unit V Ω A kHz % Dynamic characteristics (see test circuit). V5 η Voltage feedback Efficiency 4.4 V