AN3352

Block diagram and pin function description

Doc ID 018526 Rev 3

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Block diagram and pin function description

Here below a description of the LNBH24L internal blocks that includes two completely

controlled and contain independent external components. All the specifications below must

be considered equal for both sections (A/B).

1.1

Step-up controller

The LNBH24L features a built-in step-up DC-DC converter that, from a single supply source

ranging from 8 V to 15 V, generates the voltages that allow the linear post-regulator to work

with minimum power dissipation. The external components of the DC-DC converter are

1.2

Pre-regulator block

This block includes a voltage reference connected to the BYP pin, an undervoltage lockout

threshold (6.7 V typ), and a power-on reset that sets all the I²C registers to zero when the

1.3

I²C interface and diagnostic

The main functions of the device are controlled via the I²C bus by writing 5 bits on the

system register (SR bits in write mode). In the same register there are 5 bits that can be

read back (SR bits in read mode) and provide 2 diagnostic functions, whereas the other 3

bits are for internal use (TEST1, TEST2, and TEST3).

Two bits report the diagnostic status of the two internal monitoring functions:

– OTF: overtemperature flag. If an overheating occurs (junction temperature exceeds

150 °C), the OTF I²C bit is set to “1”.

– OLF: overload flag. If the output current required exceeds the current limit threshold

or a short-circuit occurs, the OLF I²C bit is set to “1”.

Moreover, three bits report the last output voltage register status (EN, VSEL, LLC) received

by the I²C. The LNBH24L I²C interface address can be selected from two different

addresses for each section A/B by setting the voltage level of the relevant ADDR pin

according to Table 1:

Table 1.

LNBH24L I²C addresses

Section

Pin Set-up

Write (HEX)

Read (HEX)

A

ADDR-A=low or floating

10

11

ADDR-A=high

12

13

B

ADDR-B=low or floating

14

15

ADDR-B=high

16

16