Datasheet

6
LT1510/LT1510-5
TYPICAL PERFORMANCE CHARACTERISTICS
U
W
SWITCH CURRENT (A)
0 0.2 0.4 0.6 0.8 1.0 1.2
1.4 1.8 2.01.6
BOOST CURRENT (mA)
50
45
40
35
30
25
20
15
10
5
0

1510 G07

V
CC
= 16V
V
BOOST
= 38V
28V
18V
Switch Current vs Boost Current
vs Boost Voltage
TEMPERATURE (°C)
0
REFERENCE VOLTAGE (V)
2.470
2.468
2.466
2.464
2.462
2.460
2.458
25
50 75 100
1510 G14
125 150
Reference Voltage vs
Temperature
V
BOOST
(V)
4268
MAXIMUM DUTY CYCLE (%)
16 18 20
96
95
94
93
92
91
90
89
88
87
86
LT1510 • TPC15
10 12 14 22
V
BOOST
vs
Maximum Duty Cycle
PIN FUNCTIONS
UUU
GND: Ground Pin.
SW: Switch Output. The Schottky catch diode must be
placed with very short lead length in close proximity to SW
pin and GND.
V
CC
: Supply for the Chip. For good bypass, a low ESR
capacitor of 10µF or higher is required, with the lead length
kept to a minimum. V
CC
should be between 8V and 28V
and at least 2V higher than V
BAT
for V
BAT
less than 10V, and
2.5V higher than V
BAT
for V
BAT
greater than 10V. Under-
voltage lockout starts and switching stops when V
CC
goes
below 7V. Note that there is a parasitic diode inside from
SW pin to V
CC
pin. Do not force V
CC
below SW by more
than 0.7V with battery present. All V
CC
pins should be
shorted together close to the pins.
BOOST: This pin is used to bootstrap and drive the switch
power NPN transistor to a low on-voltage for low power
dissipation. In normal operation, V
BOOST
= V
CC
+ V
BAT
when switch is on. Maximum allowable V
BOOST
is 55V.
SENSE: Current Amplifier CA1 Input. Sensing can be at
either terminal of the battery. Note that current sense
resistor R
S1
(0.08Ω) is between Sense and BAT pins.
BAT: Current Amplifier CA1 Input.
PROG: This pin is for programming the charging current
and for system loop compensation. During normal opera-
tion, V
PROG
stays close to 2.465V. If it is shorted to GND
the switching will stop. When a microprocessor-controlled
DAC is used to program charging current, it must be
capable of sinking current at a compliance up to 2.465V.
V
C
: This is the control signal of the inner loop of the current
mode PWM. Switching starts at 0.7V and higher V
C
corresponds to higher charging current in normal opera-
tion. A capacitor of at least 0.1µF to GND filters out noise
and controls the rate of soft start. To shut down switching,
pull this pin low. Typical output current is 30µA.
OVP: This is the input to the amplifier VA with a threshold
of 2.465V. Typical input current is about 50nA into pin. For
charging lithium-ion batteries, VA monitors the battery
voltage and reduces charging current when battery volt-
age reaches the preset value. If it is not used, the OVP pin
should be grounded.