ZHCSI53A May 2018 – November 2018 LM5122ZA
PRODUCTION DATA.
The LM5122ZA allows 100% duty cycle operation for the high-side synchronous switch when the input supply voltage is equal to or greater than the target output voltage. An internal 200 μA BST charge pump maintains sufficient high-side driver supply voltage to keep the high-side N-channel MOSFET switch on without the power stage switching. The internal BST charge pump is enabled when the UVLO pin voltage is greater than 1.2 V and the VCC voltage exceeds the VCC UV threshold. The BST charge pump generates 5.3-V minimum BST to SW voltage when SW voltage is greater than 9 V. This requires minimum 9 V boost output voltage for proper bypass operation. The leakage current of the boot diode should be always less than the BST charge pump sourcing current to maintain a sufficient driver supply voltage at both low and high temperatures. Forced-PWM mode is the recommended PWM configuration when bypass operation is required.