9 Power Supply Recommendations

The recommended bias supply voltage range for LM2104 is from 9 V to 18 V. The lower end of this range is governed by the internal undervoltage lockout (UVLO) protection feature of the V_GVDD supply circuit blocks. The upper end of this range is driven by the 18-V recommended maximum voltage rating of the GVDD pin. It is recommened that the voltage on GVDD pin is lower than the maximum recommended voltage to account for transient voltage spikes.

The UVLO protection feature also involves a hysteresis function. This means that once the device is operating in normal mode, if the V_GVDD voltage drops, the device continues to operate in normal mode as long as the voltage drop does not exceed the hysteresis specification, V_DDHYS. If the voltage drop is more than hysteresis specification, the device shuts down. Therefore, while operating at or near the 9-V range, the voltage ripple on the auxiliary power supply output must be smaller than the hysteresis specification of LM2104 to avoid triggering device-shutdown.

A local bypass capacitor must be placed between the GVDD and GND pins and this capacitor must be located as close to the device as possible. A low-ESR, ceramic surface mount capacitor is recommended. TI recommends using two capacitors across GVDD and GND: a low capacitance ceramic surface-mount capacitor for high-frequency filtering placed very close to GVDD and GND pins, and another high capacitance value surface-mount capacitor for IC bias requirements. In a similar manner, the current pulses delivered by the GH pin are sourced from the BST pin. Therefore, a local decoupling capacitor is recommended between the BST and SH pins.