ASL1507SHN datasheet(21/56 Pages) NXP

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NXP Semiconductors

ASL1507SHN; ASL2507SHN

Single-phase and two-phase boost converter with limp-home mode

ASL1507_ASL2507

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Product data sheet

Rev. 1 — 26 April 2018

21 / 56

8.5 Coil peak current limitation

The ASL1507SHN; ASL2507SHN 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. It also allows some soft start feature to

be realized with this function.

With the maximum phase current VOx register, the maximum peak current for the

phase can be configured. Once the voltage between pins SNLx and SNHx achieves

maximum level, the gate will be turned off until the next switching cycle. To avoid

subharmonic oscillations when the coil peak current limitation is becoming active, the

slope compensation remains active. It reduces the coil peak current toward the end of the

switching cycle to ensure stable operation of the system.

In order to avoid that this function interferes with the normal regulation, the limit should

be placed well above the maximum expected current.

Table 31. Maximum coil current VO1 register (address 07h)

Bit

Symbol

Description

Value

Function

00h

no current allowed

...

maximum peak current = (IMAX1[7:0] × 1.8 V / 256 − 0.24 V) / Rsense

80h

maximum allowed setting = (128 / 255 × 1.8 V − 0.24 V) / Rsense

...

not allowed

7 to 0 IMAX1[7:0]

coil current

limitation

assigned to VO1

FFh

not allowed

Table 32. Maximum coil current VO2 register (address 08h)

Bit

Symbol

Description

Value

Function

00h

no current allowed

...

maximum peak current = (IMAX2[7:0] × 1.8 V / 256 − 0.24 V) / Rsense

80h

maximum allowed setting = (128 / 255 × 1.8 V − 0.24 V) / Rsense

...

not allowed

7 to 0 IMAX2[7:0]

coil current

limitation

assigned to VO2

FFh

not allowed

8.6 Enabling the output voltage

The ASL1507SHN; ASL2507SHN provides two independent output voltages. In

operation mode, the output voltages are turned on with the bit VO1EN and VO2EN.

As soon as one of the outputs is turned on, the VGG voltage regulator is turned on. After

tstartup the gate drivers start switching, provided the bit VGG_OK is set.

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