LT1620 Linear Technology, LT1620 Datasheet - Page 4

• Manufacturer Part Number: LT1620
• Description: Rail-to-Rail Current Sense Amplifier
• Manufacturer: Linear Technology

LT1620/LT1621
input (across external sense resistor) equal to (V
V
AVG2: Sense Amplifier A
Positive Input. Used as integration node for end-of-cycle
determination flag. Integration time constant is calculated
using 5k typical output impedance.
PROG2: Comparator Negative Input. Program node for
end-of-cycle determination typically used during voltage
mode operation. The comparator threshold is reached
when the current sense amplifier differential input voltage
FUNCTIONAL BLOCK DIAGRA
Current Sense Amplifier
The current sense amplifier is a multiple output voltage
amplifier with an operational input common mode range
from 0V to 32V. The amplifier generates scaled output
voltages at the SENSE, AVG and AVG2 (available in
LT1620GN) pins. These output signal voltages are refer-
enced to the V
internal V
4
PI FU CTIO S
RESISTOR
OPERATION
CURRENT
PROG
SENSE
U
U
)/10. Input voltage range is V
CC
V
U
ID
referred resistors.
+
U
–
CC
supply by pulling signal current through
U
+
–
U
(Refer to the Functional Block Diagram)
V
*AVAILABLE IN THE LT1620GN ONLY
IN
PROG
= – 20 Output and Comparator
IN
PROG2*
V
CC
–
+
+
AMPLIFIER
–
SENSE
CC
to (V
CC
500
– 1.25V).
W
2.5k
CC
–
5k
GND
equals (V
0.15V) to (V
GND: Ground Reference.
MODE: Comparator Open Collector Output. Output is logic
low when magnitude of current sense amplifier differential
input voltage is less than (V
I
cation, I
companion PWM controller IC, facilitating current mode
loop control.
The first output (SENSE) is a unity gain, level-shifted repre-
sentation of the input signal (IN
charger type applications, this output is used to drive the
current sense amplifier of the mated PWM controller IC.
The other two outputs (AVG and AVG2) are internally
connected to a transconductance amplifier and compara-
tor, respectively. The AVG output yields a gain of 10, and
the AVG2 output provides a gain of 20. These pins are
OUT
: Transconductance Amplifier Output. In typical appli-
+
–
OUT
CC
–
+
CC
– V
sinks current from current-setting node on
g
m
– 2.5V).
( 1 GAIN)
( 10 GAIN)
( 20 GAIN)
PROG2
LT1620/21 • FBD
)/20. Input voltage range is (V
MODE*
SENSE
AVG2*
AVG
I
OUT
CC
– V
+
– IN
PROG2
–
). In typical PWM/
)/20.
END-OF-CYCLE
(ACTIVE LOW)
I
SENSE
SENSE
TH
CONTROLLER
INTV
PWM
+
–
5V
CC
CC
–