ASL4501SHN datasheet(16/43 Pages) NXP

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ASL4501SHN

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Product data sheet

Rev. 2 — 10 January 2018

16 of 43

NXP Semiconductors

ASL4501SHN

Four-phase boost converter

8.3.2 Output overvoltage protection programming

Due to fast changes in the supply or the output, it is possible that the output voltage is

disturbed. To avoid high voltages that may result into damage of attached components,

the ASL4501SHN offers a programmable overvoltage protection threshold. Once the

output voltage is above this threshold, the gate pin of the output stops toggling. It results in

a halt of the energy delivery to the output.

Once the output voltage recovers and is below the threshold again, the gate pin starts

toggling again. The regulation loop regulates the output back to the target value.

For stable operation of the device, the limit voltage output register should be programmed

around 5 V higher than the output voltage registers.

8.4 Coil peak current limitation

The ASL4501SHN offers a function to limit peak current inside the coil and therefore to

limit the input current for the system. Furthermore, this functionality can be used to avoid

magnetic saturation of the coils and allow some soft start feature to be realized.

With the maximum phase current Voutx registers, the maximum peak current for the

individual phases assigned to the output can be configured. Once the voltage drop

between pins SNLx and SNHx reaches this level, the gate will be turned off until the next

switching cycle. To avoid sub harmonic oscillations when the coil peak current limitation is

becoming active, the slope compensation is still active. It reduces the coil peak current

toward the end of the switching cycle to ensure stable operation of the system.

To avoid that this function interferes with the normal regulation, the limit should be placed

well above the maximum expected currents.

Table 20.

Limit voltage output 1 register (address 05h)

Bit

Symbol

Description

Value Function

7 to 0 Vmax_Vout_1[7:0]

limit output 1

00h

output 1 is turned off

...

output overvoltage protection output 1 =

0.3555

 V_Vout_1[7:0]  (1 + (333  106)  (T_junction[7:0]  38))

FFh

maximum output overvoltage protection output 1 = 90 V

Table 21.

Limit voltage output 2 register (address 06h)

Bit

Symbol

Description

Value Function

7 to 0 Vmax_Vout_2[7:0]

limit output 2

00h

output 2 is turned off

...

output overvoltage protection output 2 =

0.3555

 V_Vout_2[7:0]  (1 + (333  106)  (T_junction[7:0]  38))

FFh

maximum output over voltage protection output 2 = 90 V

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