Datasheet

4
LT1571 Series
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LT1571 is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3: Sense resistor R
S1
and package bond wires.
Note 4: Current (≈ 700µA) flows into the pins during normal operation and
also when an external shutdown signal on the V
C
pin is greater than 0.3V.
Current decreases to ≈ 200µA and flows out of the pins when external
shutdown holds the V
C
pin below 0.3V but above shutdown threshold.
Current drops to near zero when input voltage collapses. See External
Shutdown in Applications Information section.
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C.
V
CC
= 16V (LT1571-1, LT1571-2), V
CC
= 10V (LT1571-5), V
BAT
= 8V (LT1571-1,LT1571-2), V
BAT
= 4V (LT1571-5), no load on any
outputs unless otherwise noted. (Note 6)
Note 5: A linear interpolation can be used for reference voltage
specification between 0°C and –40°C.
Note 6: Maximum allowable ambient temperature may be limited by power
dissipation. Parts may not necessarily be operated simultaneously at
maximum power dissipation and maximum ambient temperature.
Temperature rise calculations must be done as shown in the Applications
Information section to ensure that maximum junction temperature does
not exceed the 125°C limit. With high power dissipation, maximum
ambient temperature may be less than 70°C.
Note 7: 91% maximum duty cycle is guaranteed by design if V
BAT
or V
X
(see Figure 8 in Application Information) is kept between 3V and 5V.
Note 8: See “Lithium-Ion Charging Completion” in the Applications
Information section.
ELECTRICAL CHARACTERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
Switch
Switch ON Resistance I
SW
= 1.5A, V
BOOST
– V
SW
≥ 2V ● 0.3 0.5 Ω
I
SW
= 1A, V
BOOST
– V
SW
< 2V (Unboosted) ● 2.0 Ω
∆I
BOOST
/∆I
SW
During Switch ON V
BOOST
= (V
CC
+ 8V), I
SW
≤ 1A 20 35 mA/A
Switch OFF Leakage Current V
SW
= 0V, V
CC
≤ 20V 2 100 µA
V
SW
= 0V, 20V < V
CC
≤ 26V 4 200 µA
Maximum V
BAT
with Switch ON ● V
CC
– 2 V
Minimum I
PROG
for Switch ON 1427 µA
Minimum I
PROG
for Switch OFF ● 1 2.4 mA
Current Sense Amplifier Inputs (SENSE, BAT)
Sense Resistance (R
S1
) 0.08 0.12 Ω
Total Resistance from SENSE to BAT (Note 3) 0.2 0.25 Ω
BAT Bias Current (Note 4) V
C
< 0.3V –200 –375 µA
V
C
> 0.6V ● 700 1300 µA
V
C
< 40mV 5 µA
Oscillator
Switching Frequency LT1571-1, LT1571-2 180 200 220 kHz
LT1571-5 440 500 550 kHz
Switching Frequency Tolerance All Conditions of V
CC
, Temperature,
LT1571-1, LT1571-2 ● 170 200 230 kHz
LT1571-1, LT1571-2, T
J
< 0°C 160 230 kHz
LT1571-5 ● 425 500 575 kHz
LT1571-5, T
J
< 0°C 400 575 kHz
Maximum Duty Cycle LT1571-1, LT1571-2 ● 87 %
LT1571-1, LT1571-2, T
A
= 25°C (Note 7) 90 93 %
LT1571-5
● 77 81 %
Current Amplifier (CA2)
Transconductance V
C
= 1V, I
VC
= ±1µA 125 210 550 µmho
Maximum V
C
for Switch OFF ● 0.6 V
I
VC
Current (Out of Pin) V
C
≥ 0.6V 100 µA
0.2V < V
C
< 0.45V 3 mA
V
C
< 40mV (Shutdown) 300 µA