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3
LTC1734
The q denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, GND = 0V and VBAT is equal to the float voltage unless
otherwise noted. All currents into device pins are positive. All currents out of device pins are negative. All voltages are referenced to
GND, unless otherwise specified.
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Charger Manual Control
VMSDT
Manual Shutdown Threshold
VPROG Increasing
q
2.05
2.15
2.25
V
VMSHYS
Manual Shutdown Hysteresis
VPROG Decreasing
90
mV
IPROGPU
Programming Pin Pull-Up Current
VPROG = 2.5V
– 6
– 3
– 1.5
A
Protection
IDSHRT
Drive Output Short-Circuit Current Limit
VDRIVE = VCC
q
35
65
130
mA
PIN FUNCTIONS
UU
U
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC1734E is guaranteed to meet performance specifications
from 0
°C to 70°C ambient temperature range and 0°C to 100°C junction
temperature range. Specifications over the – 40
°C to 85°C operating
ambient temperature range are assured by design, characterization and
correlation with statistical process controls.
Note 3: Assumes that the external PNP pass transistor has negligible B-C
reverse-leakage current when the collector is biased at 4.2V (VBAT) and the
base is biased at 5V (VCC).
Note 4: Assumes that the external PNP pass transistor has negligible B-E
reverse-leakage current when the emitter is biased at 0V (VCC) and the
base is biased at 4.2V (VBAT).
ISENSE (Pin 1): Sense Node for Charge Current. Current
from VCC passes through the internal current sense resis-
tor and reappears at ISENSE to supply current to the
external PNP’s emitter. The PNP’s collector provides
charge current to the battery.
GND (Pin 2): Ground. Provides a reference for the internal
voltage regulator and return for all internal circuits. When
in the constant voltage mode, the LTC1734 will precisely
regulate the voltage between the BAT and GND pins. The
battery ground should tie close enough to the GND pin to
avoid voltage drop errors.
VCC (Pin 3): Positive Input Supply Voltage. This pin
supplies power to the internal control circuitry and exter-
nal PNP transistor through the internal current sense
resistor. This pin should be bypassed to ground with a
capacitor in the range of from 1
F to 10F.
PROG (Pin 4): Charge Current Programming, Charge
Current Monitor and Manual Shutdown Pin. Provides a
virtual reference voltage of 1.5V for an external resistor
(RPROG) tied between this pin and ground that programs
the battery charge current while the charger is in the
constant current mode. The typical charge current will be
1000 times the current through this resistor (IBAT = 1500/
RPROG). This pin also allows for the charge current to be
monitored. The voltage on this pin is proportional to the
battery charging current so that at C/10 the voltage will be
1.5V/10. Floating the pin allows an internal current source
to pull the pin voltage above the shutdown threshold
voltage. Because this pin is in a signal path, excessive
capacitive loading can cause AC instability. See the Appli-
cations Information section for more details.
BAT (Pin 5): Battery Voltage Sense Input. A precision
internal resistor divider sets the final float voltage on this
pin. This divider is disconnected in the manual shutdown
or sleep mode. When charging, approximately 34
A
flows into the BAT pin. To minimize float voltage errors,
avoid excessive resistance between the battery and the
BAT pin. For dynamically stable operation, this pin re-
quires a minimum bypass capacitance to ground of 5
F
to frequency compensate for the high frequency inductive
effects of the battery and wiring.
DRIVE (Pin 6): Base Drive Output for the External PNP
Pass Transistor. Provides a controlled sink current that
drives the base of the PNP. This pin has current limiting
protection.