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SMB135E-470V View Datasheet(PDF) - Summit Microelectronics

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SMB135E-470V Datasheet PDF : 34 Pages
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SMB135
APPLICATIONS INFORMATION (CONTINUED)
Frequency Selection
The SMB135 can operate at three different switching
frequencies (750kHz, 1MHz, 1.25MHz), which are
selectable via an I2C command (Register 08h).
STAT Output
The STAT is an open-drain output that indicates battery
charge status or an input under-voltage/over-voltage
(UV/OV) condition. The type of indication can be
selected via the corresponding bit in Register 07h.
STAT has two modes of operation, as determined by
Register 05h[7]: in Mode 0, STAT is asserted low
whenever the battery is charging and de-asserted at all
other times; in Mode 1, STAT is de-asserted when the
charger is disabled, blinks during charging, and
remains continuously asserted when the charge cycle
has completed. A pull-up resistor should be applied on
this pin for interfacing to a microcontroller or other logic
IC.
Programmable Battery Charging
A unique feature of the SMB135 is the ability to modify
all of the important charger parameters via internally
programmable EEPROM, found in Registers 00-07.
Once the device has been configured correctly, the
EEPROM may be locked, preventing any further
changes. Additionally, these registers may also be
configured so that they may be updated in RAM
(volatile), even if the underlying EEPROM is locked.
This feature is useful if it is desired to actively manage
the charging profile without making changes to the non-
volatile defaults. Use Register 0E to control locking
and volatile access. Before writing to Registers 00-07
in a volatile manner, Register 31[7] must first be set
high.
FAULT and STATUS Indicators
A large number of battery charging conditions and
parameters are monitored and corresponding fault and
status indications are available to the user via the I2C
compatible registers. These include the following:
Charging status
Safety timer timeout
Over-temperature alarm
Under-temperature alarm
Over-voltage alarm
Under-voltage alarm
Missing battery detection
Glitch Filter
The SMB135 features a glitch filter to ensure that short
violations in the UV or OV settings will not result in a
fault-triggered action. The glitch filter is user-
programmable (Register 05h) and may be set to 0msec
(glitch filer disabled) or to 250msec. Enabling the glitch
filter will delay “automatic recharge” and “current
termination” by 250msec.
Hold-off Timer
The SMB135 features a hold-off timer that defines the
amount of time from enabling the charger output until
current begins flowing (trickle charge is excluded from
this condition). Two choices (short & long) are
available: <1msec or 256msec. The short timer is
asynchronous and could be any value between 0msec
and 1msec.
Internal Thermal Protection
When the die temperature of the SMB135 reaches
approximately 110°C, the PWM switcher will cut back
on the duty cycle to reduce current and prevent further
die heating. This internal thermal protection circuit
helps to improve device (and consequently, system)
reliability.
Summit Microelectronics, Inc
2106 3.1 11/4/2008
15
 

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