SLVSHM3 Data sheet

SLVSHM3 November 2026 TPS2HCS05-Q1

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slvshm3_oa

8.4.1.1.3 Programmable Fuse Protection

The device includes a programmable fuse protection for each channel, that is based on a defined time-current curve and is commonly referred to as I2t protection in melting fuse datasheets. The intent is to match the switch turnoff behavior of a melting fuse. The NOM_CUR_CHx [2:0] bits and I2T_TRIP_CHx [3:0] bits set the time-current curve but the device also uses a fixed delay shutdown (I_SWCL) and immediate shutdown protection (I_OCP) to create the full I2T protection for the device. The I2T protection of the TPS2HCS05-Q1 consists of four regions:

Nominal current
Fuse shutdown
Fixed delay shutdown
Immediate shutdown protection (I_OCP)

The nominal current region (1) defines the region where the device can supply current indefinitely without turning off. This is roughly equivalent to the fuse current rating of a melting fuse. This region is set by the NOM_CUR_CHx [2:0] bits and if the output current is less than the NOM_CUR_CHx setting then the device can supply current indefinitely as previously stated and does not start the I2T accumulation. If the output current is greater than or equal to the NOM_CUR_CHx setting then the device enters the I2T accumulation loop and starts to accumulate until the I2T_TRIP_CHx [3:0] threshold is met. If the output current falls back below the NOM_CUR_CHx before the I2T_TRIP_CHx value is reached then the device stops the I2T accumulation but still keeps track of the accumulated energy as long as power is provided to the device.

Above the nominal current region, is the fuse shutdown region (2) which is set by the I2T_TRIP_CHx [3:0] bits. This region defines the curvature of time-current curve and the region where the I2T accumulation of the device is active. Based on the output current level and the NOM_CUR_CHx setting the device trips at different time intervals based on the I2T_TRIP value that is set. The time-current curve of the device is defined by the following equations.

If DCR_CHx = 0, then the device accumulates according to Equation 1 and decrements according to Equation 2.

Equation 1.

I 2 T_TRIP = (I_{OUT})^{2} \times t

Equation 2.

I 2 T_TRIP = ({I_{OUT}}^{2} - k \times {NOM_CUR_CHx}^{2}) \times t

Note: The decrement factor "k" in Equation 2 is determined by ACC_DCR0_CHx bits in the I2T_CONFIG_CHx register.

If DCR_CHx = 1, then devices accumulates and decrements according to Equation 3.

Equation 3.

I 2 T_TRIP = ({I_{OUT}}^{2} - {NOM_CUR_CHx}^{2}) \times t

If the accumulation does not exceed the I2T_TRIP value and the current falls below NOM_CUR_CH then Equation 2 or Equation 3 depending on the DCR_CHx setting is used to decrement the accumulated energy based on the ISNS value until the accumulated energy reaches zero. While the device continues to decrement down to zero, the I2T_MOD bit remains 1 until accumulated energy returns back to zero and then the I2T_MOD bit sets back to zero. If any conversions are disabled due to a channel entering the I2T loop then those conversions are re-enabled when I2T_MOD = 0.

Above the fuse shutdown region, is the fixed delay shutdown region (3) where the device provides a fixed delayed shutdown that is set by the ISWCL_CHx [1:0] and SWCL_DLY_TMR_CHx [1:0] bits. The ISWCL_CHx [1:0] sets the output current value and the SWCL_DLY_TMR_CHx sets the time. If the output current exceeds the ISWCL_CHx level continuously for SWCL_DLY_TMR_CHx then the channel immediately turns off.

If a shutdown occurs either due to the I2T_TRIP_CHx value being exceeded or due to the ISWCL_CHx function, the device remains off for a period set by the TCLDN_CHx [1:0]. If the TCLDN_CHx [1:0] = 00 then the device remains off and does not retry. To retry in this setting, the TCLDN_CHx [1:0] bits need to be changed to another setting. Once the setting has been changed, the device retries after the defined cool down time of the new setting. Note, when the channel enters the I2T shutdown state the accumulator value resets to 0 so the retry time must be adjusted to make sure enough time has elapsed for the wire harness to cool down. Also note, when the channel enters the I2T shutdown state, the values for NOM_CUR_CHx, I2T_TRIP_CHx, and ISWCL_CHx cannot be changed.

Above the fixed delay shutdown region, is the immediate shutdown overcurrent protection (I_OCP) region (4). This region is set by the ILIMIT_SET_CHx [3:0] bits. If the output current exceeds the I_OCP level then the device turns off immediately. The retry or latched off behavior for the I_OCP is set by the LATCH_CHx bit and described in the next section.

These operational regions for the I2T protection are show in Figure 8-28.

TPS2HCS05-Q1 Operational Region of Fuse Based Shutdown

Figure 8-28 Operational Region of Fuse Based Shutdown

The values for the NOM_CUR_CHx, I2T_TRIP_CHx, and ISWCL_CHx in the register map are based on an R_SNS value of 700Ω. The device offers the flexibility for these values to be scaled based on different R_SNS values. The equations for scaling the NOM_CUR_CHx, I2T_TRIP_CHx, and the ISWCL_CHx are defined below.

Equation 4.

{N O M_C U R}_{A D J, T Y P} = \frac{{N O M_C U R}_{700} \times 700}{R_{S N S, A D J, T Y P}}

Equation 5.

I_{S W C L, A D J, T Y P} = \frac{I_{S W C L, 700} \times 700}{R_{S N S, A D J, T Y P}}

Equation 6.

{I 2 T}_{A D J . T Y P} = {I 2 T}_{700} \times ({\frac{700}{R_{S N S, A D J, T Y P}})}^{2}

where,

Equation 7.

{N O M_C U R}_{700} = {N O M_C U R_C H x}_{} v a l u e i n t h e d a t a s h e e t b a s e d o n R_{S N S} o f 700 Ω

Equation 8.

I_{S W C L, 700} = I_{S W C L} v a l u e i n t h e d a t a s h e e t b a s e d o n R_{S N S} o f 700 Ω

Equation 9.

{I 2 T}_{700} = {I 2 T t r i p}_{} v a l u e i n t h e d a t a s h e e t b a s e d o n R_{S N S} o f 700 Ω