LT1621_15 Datasheet, PDF (1/12 Pages) Linear Technology – Rail-to-Rail Current Sense Amplifier

LT1620/LT1621
Rail-to-Rail Current
Sense Amplifier
FEATURES
s _{Accurate Output Current Programming}
s _{Usable in Charging Applications Up to 32V Output}
s _{Programmable Load Current Monitor for End-of-}
Charging-Cycle Notification (16-Pin Version)
s _{Dual Function IC (LT1621) Allows Convenient}
Integration of Load and Input Current Sensing
s _{Level-Shifted Current Sense Output for Current Mode}
PWM Controllers
s _{Can be Used for NiCd, NiMH, Lead-Acid and Lithium-}
Ion Battery Charging
s _{Greater than 96% Efficiency Possible in Charger}
Applications
s _{High Output Currents Possible: > 10A}
Easily Obtained
APPLICATI S
s _{High Current Battery Chargers}
s _{High Output Voltage DC/DC Converters}
s _{Constant Current Sources}
s _{Overcurrent Fault Protectors}
DESCRIPTIO
The LT ^®1620 simplifies the design of high performance,
controlled current battery charging circuits when used in
conjunction with a current mode PWM controller IC.
The LT1620 regulates average output current independent
of input and output voltage variations. Output current can
be easily adjusted via a programming voltage applied to
the LT1620’s PROG pin.
Most current mode PWM controllers have limited output
voltage range because of common mode limitations on the
current sense inputs. The LT1620 overcomes this restric-
tion by providing a level-shifted current sense signal,
allowing a 0V to 32V output voltage range.
The 16-pin version of the LT1620 contains a program-
mable low charging current flag output. This output flag
can be used to signal when a Li-Ion battery charging cycle
is nearing completion.
The LT1621 incorporates two fully independent current
control circuits for dual loop applications.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATI
V_IN
LTC1435
SYNCHRONOUS
BUCK
REGULATOR
(V_BATT + 0.5V) TO 32V
+ 22µF
35V
×2
V_IN
I_BATT TO 4A
6
0.1µF
1
V_CC
SENSE
AVG
8
2 _IOUT
PROG ⁷
LT1620MS8
3
GND
4 _IN–
IN^{+ 5}
I_TH
SW
SENSE^–
27µH ^0.025Ω
INTV_CC
FB
0.1µF
3k
1%
15.75k
1%
1.43M
0.1%
+
22µF
35V
110k
0.1%
SIMPLIFIED SCHEMATIC. SEE FIGURE 2 FOR COMPLETE SCHEMATIC
LT1620/21 • F01
Figure 1. Low Dropout, High Current Li-Ion Battery Charger
V_BATT
100
V_IN = 24V
95
90
85
Efficiency
V_BATT = 16V
V_BATT = 12V
V_BATT = 6V
80
75
0
1
2
3
4
5
BATTERY CHARGE CURRENT (A)
1620/21 • TA02
1