LT1505CG Linear Technology, LT1505CG Datasheet - Page 14

• Manufacturer Part Number: LT1505CG
• Description: IC BATT CHARGER CONST I/V 28SSOP
• Manufacturer: Linear Technology

Specifications of LT1505CG

• Function: Charge Management
• Battery Type: Li-Ion, NiCd, NiMH
• Voltage - Supply: 11 V ~ 24 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP (0.200", 5.30mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIONS
LT1505
amplifier CA1. They are not needed if V
higher than V
replaced with a diode if V
The gate control pin INFET turns on M3 when V
above the undervoltage lockout level set by R5 and R6 and
is clamped internally to 8V below V
V
Shutdown
When adapter power is removed, V
be held by the body diode of the topside NFET switch. As
soon as V
go into sleep mode drawing only 10 A from the battery.
There are two ways to stop switching: pulling the SHDN
pin low or pulling the V
will also turn off V
V
Make sure there is a pull-up resistor on the SHDN pin even
if the SHDN pin is not used, otherwise internal pull-down
current will keep the SHDN pin low and switching off when
power turns on.
Each TGATE and BGATE pin has a 50k pull-down resistor
to keep the external power FETs off when shut down or
power is off.
Note that maximum operating V
transients the LT1505 can be operated as high as 27V. For
V
down. If the SHDN pin has to be used to shut down at V
higher than 24V, the Figure 6 pull-up circuit must be used
to slow down the V
is released. Otherwise, high surge current charging the
bypass capacitor might damage the LT1505. For V
than 24V, only a 100k resistor and no capacitor is needed
at SHDN pin to V
Synchronization
The LT1505 can be synchronized to a frequency range
from 240kHz to 280kHz. With a 200ns one-shot timer on
chip, the LT1505 provides flexibility on the synchronizing
pulse width. Sync pulse threshold is about 1.2V (Figure 7).
14
IN
C
CC
pin low will only stop switching and V
is removed, INFET will clamp M3 V
higher than 24V it is preferred to use the V
CC
goes down to 0.2V above V
BAT
IN
GBIAS
. The PFET M3 is optional and can be
GBIAS
U
for pull-up.
C
and CA1 input currents. Pulling the
pin low. Pulling the SHDN pin low
ramp-up rate when the SHDN pin
IN
INFORMATION
U
is at least 3V higher than V
CC
CC
CC
W
. In sleep mode when
BAT
will drift down and
is 24V. For short
CC
SG
GBIAS
, the LT1505 will
is at least 2.5V
to 0.2V.
C
stays high.
pin to shut
U
IN
gets up
CC
BAT
less
CC
.
Nickel-Cadmium and Nickel-Metal-Hydride Charging
The circuit in the 4A Lithium Battery Charger (Figure 1) can
be modified to charge NiCd or NiMH batteries. For
example, 2-level charging is needed; 2A when Q1 is on,
and 200mA when Q1 is off (Figure 8).
For 2A full current, the current sense resistor (R
be increased to 0.05 so that enough signal (10mV) will
be across R
current accurate.
For a 2-level charger, R1 and R2 are found from:
R1
2.465 4000
Figure 7. Synchronizing with External Clock
PULSE WIDTH > 200ns
Figure 6. High Input Voltage Shudown
S1
I
24V V
LOW
at 0.2A trickle charge to keep charging
LT1505
Figure 8. 2-Level Charging
CC
< 27V
C
1 F
PROG
5V TO 20V
SHDN
LT1505
VN2222
5k
V
R1
49.3k
IN
PROG
3M
R2
3.3 F
SYNC
Q1
OPEN DRAIN
R2
5.49k
2.465 4000
1505 F07
I
HI
LT1505
1505 F05
1505 F06
I
LOW
S1
) should
1505fc