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SC806

POWER MANAGEMENT

CHRGB LED Flag

The CHRGB LED driver on the SC806 can be used to

drive an LED and/or signal the system processor.

CHRGB=Low (Charging) and CHRGB=High-Z (Charge Com-

plete). The CHRGB output will be high impedance when

the VCC is in a UV condition. The Table below defines the

CHRGB LED output states.

D

E

Lw

o

LZ

-

h

g

i

Hg

n

i

k

n

il

B

B

G

R

H

C

>

t

u

o

I

m

r

e

t

<

t

u

o

I

m

r

e

t

T

O

r

o

V

O

tl

u

a

F

The CHRGB output signifies the charging status. When

the output current is > Itermination, CHRGB=low. CHRGB

is high impedance when Iout is < Itermination. The

CHRGB output is latched high-Z at the end of the charge

cycle when the output current is less than Itermination.

The CHRGB output will remain high until the battery en-

ters a recharge cycle, or if EN, or VCC are toggled.

.

There are three fault modes detected by the SC806;

(Input under voltage, input over voltage, and Max die tem-

perature or OT). The LED states for these fault modes

are shown below.

t

l

u

a

FB

G

R

H

C

O

L

V

U

C

C

V

Z

-

h

g

i

H

P

V

O

C

C

V

g

n

i

k

n

il

B

0

5

1

>

j

T

o

C

g

n

i

k

n

il

B

Overcurrent and Max Temperature Protection

Overcurrent protection is inherent in all modes of opera-

tion. When the device is in charge-mode the output is

current limited to either the pre-charge current limit value

or the fast charge current limit value depending on the

voltage at the output. Max die temperature protection is

included on the SC806. This feature allows the SC806

to operate with maximum power dissipation by disabling

the output current when the die temperature reaches

OT. The result is that the SC806 will operate as a pulse

charger in extreme power dissipation applications deliv-

ering the maximum allowable output current while regu-

lating the internal die temperature to a safe level.

CPB LED Flag

The CPB LED driver on the SC806 is used to indicate

that the adapter voltage is present at the input to the

SC806. The CPB output is an active low output when

the input voltage is greater than 3V. This feature is ac-

tive regardless of the state of the DIS pin.

Layout Guidelines

The two most critical aspects of the pcb layout are the

power path and thermal layout. The power path starts

at the Adapter + input and runs to the VCC input of the

SC806, then from the Vout pin of the SC806 to the Bat-

tery + terminal, and completes with the return trace from

the battery - terminal to the adapter - input. All of these

traces need to be designed to handle the required charg-

ing current. The trace from Vout of the SC806 is most

critical and should be made as wide as possible to

minimze IR drops between the regulated voltage at the

SC806 vout pin and the battery terminal. Keep the

Adapter+ to SC806 VCC input trace wide to minimize

voltage drops that will add to the dropout voltage capa-

bility of the SC806. The GND pin of the SC806 should

be connected in a kelvin fashion at the Battery terminal

to eliminate voltage drops in the return path reducing

the regulated battery voltage.

The themal performance of the SC806 package requires

a low impedance connection from the heat slug on the

bottom of the package to an external ground plane. This

is best accomplished by using a single large via under

the device connected to a ground plane on the bottom

exposed side of the pcb. The evaluation board uses 1

square inch of copper on the bottom of the pcb and is

capable of 1A charging current.

The input and output bulk decoupling capacitors for the

SC806 should be placed near the external terminals for

the adpater and battery. This short low impedance loop

is for the high current spikes that result from input/out-

put hot-plugging of the charger. To minimize these cur-

rent spikes should be minimized. A typical application

requires a 0.1µF input/output capacitor. If the distance

from the external terminals to the SC806 is greater than

1”, 0.1µ local decoupling capacitors at the SC806 may

be required.