3
LT1620/LT1621
E
LECTR
IC
AL C CHARA TERIST
ICS
IN
+
= 16.8V, V
CC
= 5V, V
IOUT
= 2V, T
A
= 25°C unless otherwise noted.
The ● denotes specifications which apply over the full operating
temperature range.
Note 1: Absolute Maximum Ratings are those values beyond which the
life of a device may be impaired.
Note 2: Input bias currents are disabled when V
CC
is removed, even
with common mode voltage present at IN
+
, IN
–
.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Current Sense Amplifier
V
OSAVG
Input Offset - Measured at ×10 Output V
CC
≤ V
CM
≤ 32V –3 3 mV
(V
AVG
) 35mV ≤ V
ID
≤ 125mV ● –4 4 mV
V
CM
= 0V, V
ID
= 80mV ● –10 15 mV
V
OSAVG2
Input Offset - Measured at × 20 Output V
CC
≤ V
CM
≤ 32V –3 3 mV
(V
AVG2
) 0V ≤ V
ID
≤ 35mV ● –4 4 mV
V
SENSE
No-Load Output Offset 0V ≤ V
CM
≤ 32V, V
ID
= 0V, Referenced to V
CC
● –0.1 –3 mV
I
B(IN
+
, IN
–
)
Input Bias Current (Sink) V
CC
≤ V
CM
≤ 32V (Note 2) 200 270 400 µA
● 185 430 µA
Input Bias Current (Source) V
CM
= 0V (Note 2) 4.0 5.25 mA
● 5.50 mA
Transconductance Amplifier
g
m
Amplifier Transconductance 3000 3500 4000 µmho
● 2200 4800 µmho
A
V
Amplifier Voltage Gain 1V ≤ V
IOUT
≤ 3V 60 80 dB
V
OLIOUT
I
OUT
Saturation Limit (Sink) I
IOUT
= 50µA ● 0.05 0.15 V
I
IOUT
= 200µA ● 0.10 0.30 V
I
IOUT
= 1mA ● 0.35 0.65 V
V
PROG
PROG Input Range ● V
CC
– 1.25 V
CC
V
I
BPROG
Input Bias Current Measured at PROG Pin 20 nA
V
OSPROG
Input Offset Voltage I
IOUT
= 130µA–77mV
(V
AVG
– V
PROG
) ● –8 8 mV
End-of-Cycle Comparator
V
PROG2
PROG2 Input Range ● V
CC
– 2.5 V
CC
– 0.15 V
V
HYST
Input Hysteresis Measured at AVG2 Pin 15 mV
I
BPROG2
Input Bias Current Measured at PROG2 Pin 20 nA
V
OLMODE
Output Logic Low Output (Sink) I
MODE
= 0.5mA ● 0.1 0.5 V
I
MODE
= 10mA ● 0.5 1.2 V
PI FU CTIO S
U
UU
ensure continuity around zero inductor current. Typical out-
put is –3mV with differential input voltage (IN
+
– IN
–
) = 0.
AVG: Sense Amplifier A
V
= –10 Output and
Transconductance Amplifier Positive Input. Used as inte-
gration node for average current control. Integration time
constant is calculated using 2.5kΩ typical output imped-
ance.
PROG: Transconductance Amplifier Negative Input. Pro-
gram node for average current delivered to load during
current mode operation. Average current delivered to load
imposes voltage differential at current sense amplifier
V
CC
: 5V ±10% Power Supply Input.
IN
+
: Sense Amplifier Positive Input. Typically connected
to inductor side of current sense resistor. Common mode
voltage range is 0V to 32V.
IN
–
: Sense Amplifier Negative Input. Typically connected
to load side of current sense resistor. Common mode
voltage range is 0V to 32V.
SENSE: Sense Amplifier A
V
= –1 Output. Used as level-
shifted output for PWM controller current sense input. The
sense output is designed to have an inherent offset to
