Pin description – Rainbow Electronics MAX8645Y User Manual

Page 8

MAX8645X/MAX8645Y

1x/1.5x/2x White LED Charge Pumps with Two
LDOs in 4mm x 4mm TQFN

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Pin Description

PIN

NAME

FUNCTION

Supply Voltage Input. Bypass to PGND with a 10µF ceramic capacitor. The input voltage range is
2.7V to 5.5V. PIN is high impedance during shutdown.

Chip Supply Voltage Input. Bypass to GND with a 10µF ceramic capacitor as close as possible to the
IC. The input voltage range is 2.7V to 5.5V. IN is high impedance during shutdown.

GND

G r ound . C onnect G N D to system g r ound and the i np ut b yp ass cap aci tor as cl ose as p ossi b l e to the IC .

LDO1

LDO1 Output. Bypass with a 1µF ceramic capacitor to GND. LDO1 is pulled to ground through an
internal 400k

Ω resistor during shutdown.

LDO2

LDO2 Output. Bypass with a 1µF ceramic capacitor to GND. LDO2 is pulled to ground through an
internal 400k

Ω resistor during shutdown.

REFBP

Reference Filter. Bypass REFBP with a 0.01µF ceramic capacitor to GND.

SETF

Bias Current Set Input for F1, F2. The current flowing out of SETF sets the maximum (100%) bias
current into each LED. V

SETF

is internally biased to 0.6V. Connect a resistor (R

SETF

) from SETF to

GND to set the flash current. R

SETF

= 82.8 / I

LED(MAX)

. SETF is high impedance during shutdown.

SETM

Bi as C ur r ent S et Inp ut for M 1–M 4. The cur r ent fl ow i ng out of S E TM sets the m axi m um ( 100%) b i as
cur r ent i nto each LE D . V

S E T M

i s i nter nal l y b i ased to 0.6V . C onnect a r esi stor ( R

S E T M

) fr om S E TM to GN D

to set the m ai n LE D cur r ent. R

S E T M

= 138 / I

L E D ( M AX )

. S E TM i s hi g h i m p ed ance d ur i ng shutd ow n.

9, 10

F2, F1

400m A C om b i ned - C ur r ent Fl ash LE D C athod e C onnecti on and C har g e- P um p Feed b ack. C ur r ent fl ow i ng
i nto F_ i s b ased on I

S E T F

. The char g e p um p r eg ul ates the l ow est F_ vol tag e to 0.15V . Gr ound i ng any F_

i np ut for ces OU T to op er ate at ap p r oxi m atel y 5V . C onnect F_ to OU T i f thi s LE D i s not p op ul ated .

11–16

M6–M1

30mA M ai n LE D Cathod e Connecti on and C har g e- P ump Feed b ack. C ur rent fl owi ng i nto M _ i s based on the
E N _ confi g ur ation and I

S E TM

. The char ge p um p reg ulates the l owest M _ inp ut voltag e to 0.15V . Gr ound i ng

any M _ for ces OU T to oper ate at ap pr oxim atel y 5V . Connect M_ to OU T i f thi s LE D i s not p op ul ated .

Default Output-Voltage Select Input. P1 and P2 set the LDO1 and LDO2 voltages to one of nine
combinations (Table 2). P2 is high impedance in an off condition and shortly after an on condition.

ENLDO

LDO Output Enable. Drive to a logic-level high to turn on both LDOs. Drive to a logic-level low to turn
off both LDOs.

ENM2

Enable and Dimming Control for M1–M6. Drive both ENM1 and ENM2 to a logic-level high to turn on
the main LEDs. Drive both ENM1 and ENM2 to a logic-level low to turn off the main LEDs. Alternate
dimming techniques are discussed in the Applications Information section.

ENM1

ENF

Enable and Dimming Control for F1, F2. Drive ENF to a logic-level high to turn on the flash LEDs.
Drive ENF to a logic-level low to turn off the flash LEDs. Dimming techniques are discussed in the
Applications Information section.

C1N

Transfer Capacitor 1 Negative Connection. Connect a 1µF ceramic capacitor between C1P and C1N.
C1N is internally shorted to IN during shutdown.