ZHCSND7 September 2022 SN6507-Q1
PRODUCTION DATA
The SN6507-Q1 is protected from overcurrent conditions with cycle-by-cycle current limiting on both NMOS switches. OCP is disabled during soft-start. After soft-start finishes, the OCP is enabled, and the threshold is set at the programmed value. The switch current is sensed and compared to the current threshold that is programmed by the external resistor on SS/ILIM pin, RILIM. Common current limit thresholds (ILIM) and their corresponding resistor values for RILIM are listed in Table 8-3 below. Leaving the ILIM/SS pin floating is not recommended for this device.
RILIM | ILIM (Typical) |
---|---|
18 kΩ | 1.3 A |
20 kΩ | 1.2 A |
22 kΩ | 1.1 A |
24 kΩ | 1.0 A |
27 kΩ | 900 mA |
30 kΩ | 800 mA |
35 kΩ | 700 mA |
40 kΩ | 600 mA |
50 kΩ | 500 mA |
62 kΩ | 400 mA |
85 kΩ | 300 mA |
127 kΩ | 200 mA |
261 kΩ | 100 mA |
In the event of a transient overload or short circuit, if the resulting voltage dip is lower than 2.5 V (typical) on the SS/ILIM pin, the device considers it as a “soft-short” condition. In soft-shorts, the converter goes into hiccup mode: on hitting the programmed OCP threshold, the driver will be shut-off for 100 ns (typical), and then retry driving. If the OCP trips again, the cycle continues. This retry keeps occurring for entire TON time of SW1 and SW2 until OCP does not trip or a "hard-short" is triggered. During the OCP retry events, both FETs are turned OFF, and the transient peak current may go higher than OCP limit.
If the voltage dip is more than 2.5 V (typical), the devices considers it as a “hard-short” condition. The hard-short OCP threshold is fixed at 5 A (typical). If a hard-short condition lasts more than 200 μs, it indicates that the system is in a serious short-circuit fault condition, the device will fully discharge the soft-start cap and enters soft start once the short circuit is cleared. Note there is a 65 ns (typ.) response time to trigger hard-short OCP.