CLS mode :Switching capacitive loads

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ElecCheng
Level 2
Level 2
10 sign-ins 5 questions asked 10 replies posted

Hi Expert,

I find that a new function mode is added in BTG7050-2EPL, which is CLS mode :Switching capacitive loads. After reading the datasheet, I don't get a clear version about how it works. Me=ay need your help here for better understanding.

1. In BTG7050-2EPL, Figure 19 and Figure20 all shows switching capacitive loads. But they are quite different. Is there anything wrong? From my understanding, Figure 19 is the same as driving resistive load. 

2. In both Figure 19 & 20, it contains a parameter, nCLS(ACT)x. But there is no more description for this. May you help provide more explanation?

3.  As you can see Figure 20 as below, I get several confusion.

  1. what's the value of Ilim(adj)? Ilim is PWM waveform. What's its frequency and duty cycle?
  2. Vout is like step waveform. What's the voltage value for every step?

ElecCheng_0-1675246136916.png

Thank you for your great help here. Highly appreciate if you can tell more about this function. Thanks. 

BR,

CHENG

 

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1 Solution
Anshika_G
Moderator
Moderator
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First question asked 50 likes received 250 replies posted

Hello CHENG,

I will start with answering for the 3rd question first.

As you might have read that load guard has adjustable overcurrent limitation feature. So, to explain how it works, please have a look at below image:

G_Anshika_0-1675327464678.png 

Adjustable overcurrent limitation feature allows the device to set an overcurrent threshold according to system requirement and avoids high peak currents. When the device reaches the maximum load current system limit, IL_MAX, the load current will be limited permanently to the set value, i.e., ILIM(ADJ) until the implemented overtemperature protection automatically protects the device. 
This is the main reason you are seeing a rectangular like waveform and not triangular like.

Considering switch without CLS mode : 
1. During switching on capacitive loads, high peak currents occur, the temperature of device increases, triggering the overtemperature protection of the device in normal operation
mode. This self-protection function causes the IC to latch off after several restart attempts and capacitor remained uncharged and the load is not supplied.
 
2. In normal operation mode, high peak current will be limited to overcurrent limit threshold.

But with CLS mode, as soon as the current reached the overcurrent threshold, it will be limited in the same way as normal operation mode, i.e., with adjustable overcurrent limitation. When the overtemperature protection is triggered will cause the device to switch off and immediately on again as soon as the temperature goes below the over temperature limit. This enables the capacitor to be charged by what we call as pumping mode as shown in Fig 20. 

ElecCheng_0-1675246136916.png

Q.1. Figure 19 and 20 both show switching capacitive load, but they have different Vout waveform, is that right?
Ans: Fig 19 and Fig 20 both represents Vout waveforms for capacitive load. Fig 19 shows the waveform wrt time delay and slew rate and Fig 20 shows how the charging of capacitor load is done through pumping mode when overcurrent limitation is active.

Q.2.  Based on what you mentioned, 
nCLS(ACT) is only a flag indicating whether entering CLS mode. So nCLS(ACT) only has two states, 0 or 1, right?
Ans : As mentioned earlier, n(CLS)ACT shows count or number of times capacitive load switching is activated, what I wanted to say was the count will increase the count from 1 to so on,whenever the CLS mode is activated in the system. 

G_Anshika_0-1675333635069.png

It is zero when the device is not in CLS mode.


BR,
Anshika

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4 Replies
Anshika_G
Moderator
Moderator
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First question asked 50 likes received 250 replies posted

Hello,

1. Figure 19 explains about the activation of capacitive load switching after tONCLS(DELAY). It is the time delay needed to activate the CLS  mode. 
Figure 20 explains about how the capacitor is getting charged hence the step-like waveform.

Fig 19 and Fig 20.png

Figure 17 "Switching a resistive load" and fig 19 "Switching a capacitive load" are explained in the below image:


CLS mode Load guard.png

2. nCLS(ACT) shows the count or number of times capacitive load switching is activated,hence it is showing equal to 1 during the activation mode and goes to 0 when not in CLS mode.

3.

  1. what's the value of Ilim(adj)? Ilim is PWM waveform. What's its frequency and duty cycle?
    >> It is not a PWM waveform, the waveform shows load current when the overcurrent limitation is active by using the overcurrent limitation setting which is set by the OCT pin
    Adjustable overcurrent limitation:  ILIM :  0.79 A - 8.86 A

    G_Anshika_0-1675258493838.png

    PROFET load guard has the ability to adjust the overcurrent limit as per the application need in between the given range. 

Best Regards,
Anshika




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Hi Anshika,

Thanks for your patience.

1. Figure 19 and 20 both show switching capacitive load, but they have different Vout waveform, is that right?

2. Based on what you mentioned, nCLS(ACT) is only a flag indicating whether entering CLS mode. So nCLS(ACT) only has two states, 0 or 1, right?

3. For the current limit operation, my confusion is why the Ilim current lasts for a while? From my understanding, the current rises and hit the limit value, then drop. The waveform act  like triangle. But here it's like rectangular wave. Is that right? And another question is, how long does it last off before switching again? Thanks.

BR,

CHENG

 

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Anshika_G
Moderator
Moderator
Moderator
First question asked 50 likes received 250 replies posted

Hello CHENG,

I will start with answering for the 3rd question first.

As you might have read that load guard has adjustable overcurrent limitation feature. So, to explain how it works, please have a look at below image:

G_Anshika_0-1675327464678.png 

Adjustable overcurrent limitation feature allows the device to set an overcurrent threshold according to system requirement and avoids high peak currents. When the device reaches the maximum load current system limit, IL_MAX, the load current will be limited permanently to the set value, i.e., ILIM(ADJ) until the implemented overtemperature protection automatically protects the device. 
This is the main reason you are seeing a rectangular like waveform and not triangular like.

Considering switch without CLS mode : 
1. During switching on capacitive loads, high peak currents occur, the temperature of device increases, triggering the overtemperature protection of the device in normal operation
mode. This self-protection function causes the IC to latch off after several restart attempts and capacitor remained uncharged and the load is not supplied.
 
2. In normal operation mode, high peak current will be limited to overcurrent limit threshold.

But with CLS mode, as soon as the current reached the overcurrent threshold, it will be limited in the same way as normal operation mode, i.e., with adjustable overcurrent limitation. When the overtemperature protection is triggered will cause the device to switch off and immediately on again as soon as the temperature goes below the over temperature limit. This enables the capacitor to be charged by what we call as pumping mode as shown in Fig 20. 

ElecCheng_0-1675246136916.png

Q.1. Figure 19 and 20 both show switching capacitive load, but they have different Vout waveform, is that right?
Ans: Fig 19 and Fig 20 both represents Vout waveforms for capacitive load. Fig 19 shows the waveform wrt time delay and slew rate and Fig 20 shows how the charging of capacitor load is done through pumping mode when overcurrent limitation is active.

Q.2.  Based on what you mentioned, 
nCLS(ACT) is only a flag indicating whether entering CLS mode. So nCLS(ACT) only has two states, 0 or 1, right?
Ans : As mentioned earlier, n(CLS)ACT shows count or number of times capacitive load switching is activated, what I wanted to say was the count will increase the count from 1 to so on,whenever the CLS mode is activated in the system. 

G_Anshika_0-1675333635069.png

It is zero when the device is not in CLS mode.


BR,
Anshika

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Hi Anshika,

Thanks for reply! It's clear now!

BR,

CHENG 

 

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