Datasheet

LTC4268-1
4
42681fc
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
R
INPUT_SHDN
Shutdown Input Resistance With Respect to V
PORTN
l
100
kW
V
IH_ILIM
I
LIM_EN
High Level Input Voltage With Respect to V
PORTN
(Note 13)
High Level Enables Current Limit
l
4 V
V
IL_ILIM
I
LIM_EN
Low Level Input Voltage With Respect to V
PORTN
(Note 13)
l
1 V
I
VPORTN
V
PORTN
Supply Current V
PORTN
= –54V
l
3 mA
I
IN_CLASS
IC Supply Current During Classification V
PORTN
= –17.5V, V
NEG
Tied to V
PORTP
(Note 14)
l
0.55 0.62 0.70 mA
DI
CLASS
Current Accuracy During Classification 10mA < I
CLASS
< 75mA
–12.5V ≤ V
PORTN
≤ –21V (Notes 15, 16)
l
±3.5 %
R
SIGNATURE
Signature Resistance –1.5V ≤ V
PORTN
≤ –10.1V, SHDN Tied
to V
PORTN
, IEEE 802.3af Tw o -Point
Measurement (Notes 8, 9)
l
23.25 26
kW
R
INVALID
Invalid Signature Resistance –1.5V ≤ V
PORTN
≤ –10.1V, SHDN Tied
to V
PORTP
, IEEE 802.3af Tw o -Point
Measurement (Notes 8, 9)
10 11.8
kW
V
PWRGD_OUT
Active Low Power Good Output Voltage I = 1mA, V
PORTN
= –54V, PWRGD
Referenced to V
PORTN
l
0.5 V
I
PWRGD_LEAK
Active Low Power Good Output Leakage V
PORT
= 0V, V
PWRGD
= 57V
l
1 µA
V
PWRGD_OUT
Active High Power Good Output Voltage I = 0.5mA, V
PORTN
= –52V, V
NEG
= –4V
PWRGD Referenced to V
NEG
(Note 17)
l
0.35 V
V
PWRGD_VCLAMP
Active High Power Good Voltage
Limiting Clamp
I = 2mA, V
NEG
= 0V, PWRGD Referenced
to V
NEG
(Note 3)
l
12 14 16.5 V
I
PWRGD_LEAK
Active High Power Good Output Leakage V
PWRGD
= 11V With Respect to V
NEG
,
V
NEG
= V
PORTN
= –54V
l
1 µA
R
ON
On-Resistance I = 700mA, V
PORTN
= –48V, Measured
from V
PORTN
to V
NEG
(Note 16)
l
0.5 0.6
0.8
W
W
I
OUT_LEAK
V
OUT
Leakage V
PORTN
= –57V, V
PORTP
= SHDN = V
NEG
=
0V (Note 15)
l
1 µA
I
LIM_HI
Input Current Limit, High Level V
PORTN
= –54V, V
NEG
= –53V I
LIM_EN
Floating (Notes 18, 19)
l
700 750 800 mA
I
LIM_LO
Input Current Limit, Low Level V
PORTN
= –54V, V
NEG
= –53V
(Notes 18, 19)
l
250 300 350 mA
I
LIM_DISA
Safeguard Current Limit When I
LIM
is
Disabled
V
PORTN
= –54V,
V
NEG
= –52.5V I
LIM_EN
Tied to V
PORTN
(Notes 18, 19, 20)
1.2 1.45 1.65 A
f
OSC
Oscillator Frequency C
OSC
= 100pF
l
84 100 110 kHz
C
OSC
Oscillator Capacitor Value (Note 21) 33 200 pF
t
ON(MIN)
Minimum Switch on Time 200 ns
t
ENDLY
Flyback Enable Delay Time 265 ns
t
PGDLY
PG Turn-On Delay Time 200 ns
DC
ON(MAX)
Maximum Switch Duty Cycle
l
85 88 %
V
SYNC
SYNC Pin Threshold
l
1.53 2.1 V
R
SYNC
SYNC Pin Input Resistance 40
kW
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.