LT1579CS8-3#PBF Linear Technology, LT1579CS8-3#PBF Datasheet - Page 10
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LT1579CS8-3#PBF
Manufacturer Part Number
LT1579CS8-3#PBF
Description
IC LDO REG SMART DUAL 3V 8-SOIC
Manufacturer
Linear Technology
Datasheet
1.LT1579CS-5.pdf
(20 pages)
Specifications of LT1579CS8-3#PBF
Function
Back-Up Management
Battery Type
Smart Batteries
Operating Temperature
0°C ~ 125°C
Mounting Type
Surface Mount
Package / Case
8-SOIC (0.154", 3.90mm Width)
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
PIN
LT1579
out of the pin (see curve of Adjust Pin Bias Current vs
Temperature in the Typical Performance Characteristics).
A DC load of 3 A is needed on the output of the adjustable
part to maintain regulation. The adjust pin voltage is 1.5V
referenced to ground and the output voltage range is 1.5V
to 20V.
SHDN: The shutdown pin is used to put the LT1579 into
a low power shutdown state. All functions are disabled if
the shutdown pin is pulled low. The output will be off, all
logic outputs will be high impedance and the voltage
comparators will be off when the shutdown pin is pulled
low. The shutdown pin is internally clamped to 7V and
– 0.6V (one V
either by 5V logic or open collector logic with a pull-up
resistor. The pull-up resistor is only required to supply
the pull-up current of the open collector gate, normally
several microamperes. If unused, the shutdown pin can
be left open circuit. The device is active if the shutdown
pin is not connected.
SS: The secondary select pin forces the LT1579 to switch
power draw to the secondary input (V
active low. The current drawn out of V
3 A when this pin is pulled low. The secondary select pin
is internally clamped to 7V and – 0.6V (one V
the pin to be driven directly by either 5V logic or open
collector logic with a pull-up resistor. The pull-up resistor
is required only to supply the leakage current of the open
collector gate, normally several microamperes. If sec-
ondary select is not used, it can be left open circuit. The
LT1579 draws power from the primary first if the second-
ary select pin is not connected.
BACKUP: The backup flag is an open collector output
which pulls low when the LT1579 starts drawing power
from the secondary input (V
voltage is 1V when sinking 5mA, dropping to under
200mV at 20 A (see curve of Logic Flag Voltage vs
Current in the Typical Performance Characteristics). This
makes the BACKUP pin equally useful in driving both
bipolar and CMOS logic inputs with the addition of an
external pull-up resistor. It is also capable of driving
higher current devices, such as LEDs. This pin is inter-
10
U
FUNCTIONS
U
BE
), allowing the shutdown pin to be driven
U
IN2
). The BACKUP output
IN1
IN2
). This pin is
is reduced to
BE
), allowing
nally clamped to 7V and – 0.6V (one V
pin can be left open circuit. Device operation is unaffected
if this pin is not connected.
DROPOUT: The dropout flag is an open collector output
which pulls low when both input voltages drop suffi-
ciently for the LT1579 to enter the dropout region. This
signals that the output is beginning to go unregulated.
The DROPOUT output voltage is 1V when sinking 5mA,
dropping to under 200mV at 20 A (see curve of Logic
Flag Voltage vs Current in the Typical Performance Char-
acteristics). This makes the DROPOUT pin equally useful
in driving both bipolar and CMOS logic inputs with the
addition of an external pull-up resistor. It is also capable
of driving higher current devices, such as LEDs. This pin
is internally clamped to 7V and – 0.6V (one V
unused, this pin can be left open circuit. Device operation
is unaffected if this pin is not connected.
BIASCOMP: This is a compensation point for the internal
bias circuitry. It must be bypassed with a 0.01 F capaci-
tor for stability during the switch from V
LBI1: This is the noninvering input to low-battery com-
parator LB1 which is used to detect a low input/battery
condition. The inverting input is connected to a 1.5V
reference. The low-battery comparator input has 18mV of
hysteresis with more than 20 A of sink current on the
output (see Applications Information section). This pin is
internally clamped to 7V and – 0.6 (one V
this pin can be left open circuit, with no effect on normal
circuit operation. If unconnected, the pin will float to 1.5V
and the logic output of LB1 will be high impedance.
LBI2: This is the noninverting input to low-battery com-
parator LB2 which is used to detect a low input/battery
condition. The inverting input is connected to a 1.5V
reference. The low-battery comparator input has 18mV of
hysteresis with more than 20 A of sink current on the
output (see Applications Information section). This pin is
internally clamped to 7V and – 0.6V (one V
this pin can be left open circuit, with no effect on normal
circuit operation. If unconnected, the pin will float to 1.5V
and the logic output of LB2 will be high impedance.
BE
). If unused, this
IN1
BE
BE
). If not used,
). If not used,
to V
IN2
BE
.
). If