3
LT1620/LT1621
ELECTRICAL C
C
HARA TERISTICS
IN+ = 16.8V, VCC = 5V, VIOUT = 2V, TA = 25°C unless otherwise noted.
The q 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 VCC is removed, even
with common mode voltage present at IN+, IN–.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Current Sense Amplifier
VOSAVG
Input Offset - Measured at
×10 Output
VCC ≤ VCM ≤ 32V
– 3
3
mV
(VAVG)
35mV
≤ VID ≤ 125mV
q
–4
4
mV
VCM = 0V, VID = 80mV
q
–10
15
mV
VOSAVG2
Input Offset - Measured at
×20 Output VCC ≤ VCM ≤ 32V
– 3
3
mV
(VAVG2)
0V
≤ VID ≤ 35mV
q
–4
4
mV
VSENSE
No-Load Output Offset
0V
≤ VCM ≤ 32V, VID = 0V, Referenced to VCC
q
– 0.1
– 3
mV
IB(IN+, IN–) Input Bias Current (Sink)
VCC ≤ VCM ≤ 32V (Note 2)
200
270
400
A
q
185
430
A
Input Bias Current (Source)
VCM = 0V (Note 2)
4.0
5.25
mA
q
5.50
mA
Transconductance Amplifier
gm
Amplifier Transconductance
3000
3500
4000
mho
q
2200
4800
mho
AV
Amplifier Voltage Gain
1V
≤ VIOUT ≤ 3V
60
80
dB
VOLIOUT
IOUT Saturation Limit (Sink)
IIOUT = 50A
q
0.05
0.15
V
IIOUT = 200A
q
0.10
0.30
V
IIOUT = 1mA
q
0.35
0.65
V
VPROG
PROG Input Range
q
VCC – 1.25
VCC
V
IBPROG
Input Bias Current
Measured at PROG Pin
20
nA
VOSPROG
Input Offset Voltage
IIOUT = 130A– 7
7
mV
(VAVG – VPROG)
q
–8
8
mV
End-of-Cycle Comparator
VPROG2
PROG2 Input Range
q
VCC – 2.5
VCC – 0.15
V
VHYST
Input Hysteresis
Measured at AVG2 Pin
15
mV
IBPROG2
Input Bias Current
Measured at PROG2 Pin
20
nA
VOLMODE Output Logic Low Output (Sink)
IMODE = 0.5mA
q
0.1
0.5
V
IMODE = 10mA
q
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 AV = –10 Output and
Transconductance Amplifier Positive Input. Used as inte-
gration node for average current control. Integration time
constant is calculated using 2.5k
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
VCC: 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 AV = –1 Output. Used as level-
shifted output for PWM controller current sense input. The
sense output is designed to have an inherent offset to