ZHCSN39A February 2020 – November 2021 LM61480 , LM61495 , LM62460
PRODUCTION DATA
While the RESET function of the LM6x4xx resembles a standard power-good function, the functionality is designed to replace a discrete reset IC, reducing BOM cost. There are three major differences between the reset function and the normal power-good function seen in most regulators:
FAULT CONDITION INITIATED | FAULT CONDITION ENDS (AFTER WHICH tRESET_ACT MUST PASS BEFORE RESET OUTPUT IS RELEASED) |
---|---|
FB below VRESET_UV for longer than tRESET_FILTER | FB above VRESET_UV + VRESET_HYST for longer than tRESET_FILTER |
FB above VRESET_OV for longer than tRESET_FILTER | FB below VRESET_OV - VRESET_HYST for longer than tRESET_FILTER |
Junction temperature exceeds TSD_R | Junction temperature falls below TSD_F(1) |
EN low | tEN passes after EN becomes high(1) |
VIN falls low enough so that VCC falls below VCC_UVLO - VCC_UVLO_HYST. This value is called VIN_OPERATE. | Voltage on VIN is high enough so that VCC pin exceed VCC_UVLO(1) |
The threshold voltage for the RESET function is specified to take advantage of the availability of the LM6x4xx internal feedback threshold to the RESET circuit. This allows a maximum threshold of 96.5% of selected output voltage to be specified at the same time as 96% of actual operating point. The net result is a more accurate reset function while expanding the system allowance for transient response. See the output voltage error stack-up comparison in Figure 8-9.
In addition to signaling a fault upon overvoltage detection (FB above VRESET_OV), the switch node is shut down and a small, approximately 1-mA pulldown is applied to the SW node.