SC908 View Datasheet(PDF) - Semtech Corporation
Part Name
Description
MFG CO.
'SC908' PDF : 30 Pages View PDF
SC908
Applications Information (continued)
indicates that the battery voltage is below the low-battery
detect threshold, V . Table 3 gives a comprehensive
DET
description of all combinations of status output states
while the adapter input is valid for charging.
Exceptions to these charging conditions occur when
certain events happen in combination. Table 4 describes
status condition exceptions. These exceptions include
V > OVP threshold; a high over temperature condition,
VAD
in which device temperature exceeds the higher of two
over-temperature thresholds, causing charging and both
regulators to be disabled; a precharge timeout, which
may indicate a faulty battery.
The load on VSYS should not exceed 5mA. If CHRGB is
used to operate an indicator LED, it is recommended that
the CHRGB status pin be pulled up to the battery or to a
battery-powered regulated supply. Since CHRGB is
asserted only while charging the battery, the current sunk
by CHRGB will be sourced by the charger output and will
not discharge the battery.
Because VSYS is powered from VAD, it is unsuitable as a
pullup source for the FLTB and LBATB status pins. These
status pins must be powered from the battery or battery-
powered regulated supply to function as battery level
indicators when the charging adapter is not present.
VSYS pin
The voltage of the VSYS pin is regulated from the VAD input
and is present only when VAD is powered. VSYS provides
an external voltage reference and supply for the NTC
network, and a pull-up supply voltage for the CPB status
indicator. A capacitor of at least 0.1uF should be con-
nected from VSYS to ground near the pin.
Capacitor Selection
Low cost, low ESR ceramic capacitors such as the X5R and
X7R dielectric material types are recommended. The BAT
pin capacitor, C , range is 1μF to 22μF. This capacitor
BAT
functions as both the charger output capacitor and as the
switching regulator input capacitor. The VAD pin input
capacitor C is typically between 0.1μF to 2.2μF; however,
VAD
larger values will not degrade performance.
Table 4 — Status Output State, Exception Conditions
Status Pins Out-
put State
(on = low)
Adapter
Voltage
(mutually
exclusive)
Battery
Voltage
(mutually
exclusive)
Conditions
EN_NTC
(mutually
exclusive)
Charging State,
Charging Faults
(Internal signals)
Description
and
Comments
on = open drain output driver is active
off = output is not active
T = listed condition is true
F = listed condition is false
- = don’t care
Blank = mutually exclusive with another
condition
off off on off
T
T
T
VAD Overvoltage,
---
-
---F
Battery Voltage Good or Warning
off off on on
T
T- - -
-
- - - F VAD Overvoltage, Low Battery Detect
High-Over-Temperature Detection (die
off on on off - - - - - - - - - Hi OT - - - -
temperature > T ; all functions shutdown.)
OT
Pre-charge Timeout, NTC Not Disable,
off on on on F - - - - - F - -
-
---T
Adapter Voltage Good or OVP
23
Share Link: 
