Datasheet

42681fc
LTC4268-1
3
elecTrical characTerisTics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 14V, SG open, V
CMP
= 1.5V, V
SENSE
= 0V, R
CMP
= 1k, R
tON
= 90k,
R
PGDLY
= 27.4k, R
ENDLY
= 90k, unless otherwise specified.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
PORT
Supply Voltage
IEEE 802.3af System
Signature Range
Classification Range
UVLO Turn-On Voltage
UVLO Turn-Off Voltage
Voltage With Respect to V
PORTP
Pin
(Notes 6, 7, 8, 9, 10)
l
l
l
l
l
–1.5
–12.5
–37.7
–29.8
–38.9
–30.6
–57
–10.1
–21
–40.2
–31.5
V
V
V
V
V
V
TURNON
V
CC
Turn-On Voltage Voltage With Respect to GND
l
14 15.3 16.6 V
V
TURNOFF
V
CC
Turn-Off Voltage Voltage With Respect to GND
l
8 9.7 11 V
V
HYST
V
CC
Hysteresis V
TURNON
– V
TURNOFF
l
4 5.6 7.2 V
V
CLAMP
V
CC
Shunt Regulator Voltage I
VCC
= 15mA, V
UVLO
= 0V, Voltage With
Respect to GND
l
19.5 20.2 V
I
VCC
V
CC
Supply Current V
CMP
= Open (Note 11)
l
4 6.4 10 mA
I
VCC_START
V
CC
Start-Up Current V
CC
= 10V
l
180 400 µA
V
FB
Feedback Regulation Voltage
l
1.22 1.237 1.251 V
I
FB_BIAS
Feedback Pin Input Bias Current R
CMP
Open 200 nA
g
m
Feedback Amplifier
Transconductance
l
700 1000 1400 A/V
I
FB
Feedback Amplifier Source or Sink
Current
l
25 55 90 µA
V
FBCLAMP
Feedback Amplifier Clamp Voltage V
FB
= 0.9V
V
FB
= 1.4V
2.56
0.84
V
V
%V
REF
Reference Voltage Line Regulation 12V ≤ V
CC
≤ 18V
l
0.005 0.02 %/V
A
V
Feedback Amplifier Voltage Gain V
CMP
= 1.2V to 1.7V 1500 V/V
I
SFST
Soft-Start Charging Current V
SFST
= 1.5V 16 20 25 µA
I
SFST
Soft-Start Discharge Current V
SFST
= 1.5V, V
UVLO
= 0V 0.8 1.3 mA
V
CMP_THLD
Control Pin Threshold (VCMP) Duty Cycle = Min 1 V
V
PG_HIGH
,
V
SG_HIGH
PG, SG, Output High Level
l
6.6 7.4 8 V
V
PG_LOW
,
V
SG_LOW
PG, SG, Output Low Level
l
0.01 0.05 V
V
PG_SHDN
,
V
SG_SHDN
PG, SG, Output Shutdown Strength V
UVLO
= 0V; I
PG
, I
SG
= 20mA
l
1.4 2.3 V
t
PG_RISE
,
t
SG_RISE
PG, SG Rise Time C
PG
, C
SG
= 1nF 15 ns
t
PG_FALL
,
t
SG_FALL
PG, SG Fall Time C
PG
, C
SG
= 1nF 15 ns
V
SENSE_LIM
Switch Current Threshold at Maximum
V
CMP
Measured at V
SENSE+
l
88 100 110 mV
DV
SENSE
/DV
CMP
Sense Threshold vs V
CMP
0.07 V/V
V
SENSE_OC
Sense Pin Overcurrent Fault Voltage V
SENSE+
, V
SFST
< 1V
l
205 230 mV
V
IH_SHDN
Shutdown High Level Input Voltage With Respect to V
PORTN
High Level = Shutdown (Note 12)
l
3 57 V
V
IL_SHDN
Shutdown Low Level Input Voltage With Respect to V
PORTN
l
0.45 V