CS2001

The CS2001 is a smart power supply ASIC utilized in automotive airbag systems. It contains a currentmode switching regulator with a 1.2 A onchip switch and a 5.0 V, 100 mA linear regulator. The linear output capacitor must be 3.3 mF or greater with an ESR in the range of 100 mW to 1.0 W. If the ESR of the cap is less than 100 mW, a series resistor must be used. The switcher can be configured in either a boost or flyback topology. The boost topology produces energy reserve voltage V_ER which is externally adjustable (25 V maximum) through the resistor divider connected to the V_FB pin. In the event of fault conditions that produce V_FB either open or shorted, the switcher is shut down.

Under normal operating conditions (V_BAT > 8.0 V), the current loading on the linear regulator is directed through V_BAT. A low battery or loss of battery condition switches the supply for the linear regulator from V_BAT to V_ER and shuts down the switcher using the ASIC's internal "smartswitch." This switchover CS2001 feature minimizes the power dissipation in both the linear and switcher output devices and saves the cost of using a larger inductor.

The NERD (No Energy Reserve Detected) pin is a dual function output. If VOUT is not in regulation, it provides a Power On Reset function whose time interval is externally adjustable with the capacitor. This CS2001 interval can be seen on the RESETB pin, which allows for clean powerup and powerdown of the microprocessor. Once V_OUT is in regulation, the logic level of the NERD output (usually low) indicates to the microprocessor whether or not the V_ER pin is connected.

A switchedcapacitor voltage tripler accepts input voltage VER and produces output voltage V_CHG (typically V_ER + 8.0 V). This voltage is used in the system to drive highside FETs.CS2001 is capable of withstanding a 50 V peak transient voltage.The linear regulator will not shut down during this event.