LNBH29 datasheet(8/31 Pages) STMICROELECTRONICS

8 / 31 page

Application information

LNBH29

8/31

DocID023065 Rev 3

2.11

PNG: input voltage minimum detection

When input voltage (VCC pin) is lower than LPD (low power diagnostic) minimum thresholds,

the PNG I²C bit is set to “1”. Refer to Table 9 for threshold details.

2.12

COMP: boost capacitors and inductor

The DC-DC converter compensation loop can be optimized in order to properly work with

both ceramic and electrolytic capacitors (VUP pin). For this purpose, one I²C bit in the DATA

COMP=0 for electrolytic capacitors

COMP=1 for ceramic capacitors

For recommended DC-DC capacitor and inductor values refer to Section 5: Typical

application circuits and to the BOM in Table 5.

2.13

OLF: overcurrent and short-circuit protection and diagnostic

In order to reduce the total power dissipation during an overload or a short-circuit condition,

the device is provided with a dynamic short-circuit protection. The overcurrent protection

circuit works dynamically: as soon as an overload is detected, the output current is provided

only for TON time (90 ms typ.) and after that, the output is set in shutdown for a TOFF time of

typically 900 ms. Simultaneously, the diagnostic OLF I²C bit of the STATUS register is set to

“1”. After this time has elapsed, the output is resumed for a time TON. At the end of TON, if

the overload is still detected, the protection circuit cycles again through TOFF and TON. At

the end of a full TON in which no overload is detected, normal operation is resumed and the

OLF diagnostic bit is reset to LOW after a register reading is done. Typical TON + TOFF time

is 990 ms, determined by an internal timer. This dynamic operation can greatly reduce the

power dissipation in short-circuit conditions, while ensuring excellent power-on startup in

most conditions.

2.14

OTF: thermal protection and diagnostic

The LNBH29 series is also protected against overheating: when the junction temperature

exceeds 150 °C (typ.), the step-up converter and the linear regulator are shut off and the

diagnostic OTF bit in the STATUS register is set to “1”. As soon as the overtemperature

condition is removed, normal operation is automatically re-enabled, while the OTF bit is

reset to “0” after a register reading operation.

LNBH29 Datasheet(PDF) 8 Page - STMicroelectronics