Rainbow-electronics MAX8742 Bedienungsanleitung PDF herunterladen (Seite 10)

MAX8741/MAX8742

500kHz Multi-Output Power-Supply Controllers

with High Impedance in Shutdown

10 ______________________________________________________________________________________

Pin Description (continued)

SSOP TQFN

NAME FUNCTION

15 13 SEQ

Pin-Strap Input that Selects the SMPS Power-Up Sequence:

SEQ = GND: 5V before 3.3V, RESET output determined by both outputs

SEQ = REF: Separate ON3/ON5 controls, RESET output determined by 3.3V

output

SEQ = V

: 3.3V before 5V, RESET output determined by both outputs

16 14 DH5

Gate-Drive Output for the 5V, High-Side N-Channel Switch. DH5 is a floating driver

output that swings from LX5 to BST5, riding on the LX5 switching-node voltage.

17 15 LX5 Switching-Node (Inductor) Connection. Can swing 2V below ground without hazard.

18 17 BST5 Boost Capacitor Connection for High-Side Gate Drive (0.1µF)

19 18 DL5 Gate-Drive Output for the Low-Side Synchronous-Rectifier MOSFET. Swings 0 to V

20 19 PGND Power Ground

21 20 V

5V Internal Linear-Regulator Output. V

is also the supply-voltage rail for the chip.

After the 5V SMPS output has reached 4.5V (typ), V

automatically switches to the

output voltage through CSL5 for bootstrapping. Bypass to GND with 4.7µF. V

supplies up to 25mA for external loads.

22 21 V+

Battery Voltage Input, 4.2V to 30V. Bypass V+ to PGND close to the IC with a 0.22µF

capacitor. Connects to a linear regulator that powers V

23 22 SHDN

Shutdown Control Input, Active Low. Logic threshold is set at approximately 1V. For

automatic startup, connect SHDN to V+ through a 220kΩ resistor and bypass SHDN to

GND with a 0.01µF capacitor.

24 23 DL3 Gate-Drive Output for the Low-Side Synchronous-Rectifier MOSFET. Swings 0 to V

25 24 BST3 Boost Capacitor Connection for High-Side Gate Drive (0.1µF)

26 26 LX3 Switching-Node (Inductor) Connection. Can swing 2V below ground without hazard.

27 27 DH3

Gate-Drive Output for the 3.3V, High-Side N-Channel Switch. DH3 is a floating driver

output that swings from LX3 to BST3, riding on the LX3 switching-node voltage.

28 28 RUN/ON3 ON/OFF Control Input. See the Power-Up Sequencing and ON/

OFF

Controls section.

—

6, 16, 25, 32

N.C. No Connection

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 ... 32 33

MAX8741/MAX8742 1

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