LTC4252-1CMS8 Linear Technology, LTC4252-1CMS8 Datasheet - Page 15

• Manufacturer Part Number: LTC4252-1CMS8
• Description: IC CNTRLR HOTSWAP NEGVOLT 8-MSOP
• Manufacturer: Linear Technology
• Type: Hot-Swap Controllerr

Specifications of LTC4252-1CMS8

• Applications: General Purpose
• Internal Switch(s): No
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
• Family Name: LTC4252-1
• Package Type: MSOP
• Operating Temperature (min): 0C
• Operating Temperature (max): 70C
• Operating Temperature Classification: Commercial
• Product Depth (mm): 3mm
• Product Height (mm): 0.86mm
• Product Length (mm): 3mm
• Mounting: Surface Mount
• Pin Count: 8
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: LTC42521CMS8

APPLICATIO S I FOR ATIO
tions, 30kΩ impedance coupled with 300mV UV hyster-
esis makes the LTC4252 insensitive to noise. If more noise
immunity is desired, add a 1nF to 10nF filter capacitor from
UV/OV to V
Separate UV and OV pins are available in the 10-pin MS
package and can be used for a different operating range
such as 35.5V to 76V as shown in Figure 3. Other combi-
nations are possible with different resistor arrangements.
UV/OV COMPARATORS (LTC4252A)
A UV hysteretic comparator detects undervoltage condi-
tions at the UV pin, with the following thresholds:
An OV hysteretic comparator detects overvoltage condi-
tions at the OV pin, with the following thresholds:
The UV and OV trip point ratio is designed to match the
standard telecom operating range of 43V to 71V when
connected together as in Figure 2. A divider (R1, R2) is used
to scale the supply voltage. Using R1 = 390k and R2 = 30.1k
UV low-to-high (V
UV high-to-low (V
OV low-to-high (V
OV high-to-low (V
EE
.
U
(SHORT PIN)
UV
UV
OV
OV
) = 3.08V
) = 5.09V
– V
– V
–48V
U
GND
GND
UVHST
OVHST
* M0C207
Q2: MMBT5551LT1
Figure 4. – 48V/2.5A Application with Wider Input Operating Range
464k
10k
34k
1%
1%
1%
R1
R2
R3
) = 2.756V
) = 4.988V
W
C2
10nF
C
0.68µF
T
U
10
9
8
3
UV
OV
TIMER
SS
C
68nF
SS
LTC4252A-1
V
V
EE
IN
5
1
gives a typical operating range of 43V to 71V. The under-
voltage shutdown and overvoltage recovery thresholds are
then 38.5V and 69.6V respectively. 1% divider resistors are
recommended to preserve threshold accuracy.
The R1-R2 divider values shown in Figure 2 set a standing
current of slightly more than 100µA and define an imped-
ance at UV/OV of 28kΩ. In most applications, 28kΩ
impedance coupled with 324mV UV hysteresis makes the
LTC4252A insensitive to noise. If more noise immunity is
desired, add a 1nF to 10nF filter capacitor from UV/OV to
V
The UV and OV pins can be used for a wider operating
range such as 35.5V to 76V as shown in Figure 4. Other
combinations are possible with different resistor
arrangements.
UV/OV OPERATION
A low input to the UV comparator will reset the chip and
pull the GATE and TIMER pins low. A low-to-high UV
transition will initiate an initial timing sequence if the other
interlock conditions are met. A high-to-low transition in
the UV comparator immediately shuts down the LTC4252,
pulls the MOSFET gate low and resets the latched PWRGD
high.
R
10k
1/2W
IN
EE
PWRGD
SENSE
DRAIN
GATE
.
LTC4252A-1/LTC4252A-2
2
7
6
4
22k
C
1µF
R4
LTC4252-1/LTC4252-2
IN
R
D
1M
Q2
R5
2.2k
R
10Ω
C
100µF
C
10nF
C
*
C
L
+
4252-1/2 F04
Q1
IRF530S
R
0.02Ω
S
EN
LOAD
15
425212fb