Datasheet

LM34914
SNVS453B –MAY 2006–REVISED MARCH 2013 www.ti.com
Electrical Characteristics (continued)
Limits in standard type are for T
J
= 25°C only; limits in boldface type apply over the junction temperature (T
J
) range of -40°C
to +125°C. Minimum and Maximum limits are specified through test, design, or statistical correlation. Typical values represent
the most likely parametric norm at T
J
= 25°C, and are provided for reference purposes only. Unless otherwise stated the
following conditions apply: V
IN
= 12V, R
ON
= 200kΩ
(1)(2)
.
Symbol Parameter Conditions Min Typ Max Units
Switch Characteristics
Rds(on) Buck Switch Rds(on) I
TEST
= 200 mA 0.33 0.7 Ω
UVLO
GD
Gate Drive UVLO V
BST
- V
SW
Increasing 3.0 4.2 5.5 V
UVLO
GD
hysteresis 470 mV
Softstart Pin
V
SS
Pull-up voltage 2.5 V
I
SS
Internal current source 12.5 µA
Current Limit
I
LIM
V
IN
= 8V, V
FB
= 2.4V 1.0 1.2 1.4
Threshold V
IN
= 30V, V
FB
= 2.4V 0.9 1.1 1.3 A
V
IN
= 30V, V
FB
= 1.0V 0.85 1.05 1.25
Response time 150 ns
On Timer
t
ON
- 1 On-time (normal operation) V
IN
= 10V, R
ON
= 200 kΩ 2.1 2.8 3.4 µs
t
ON
- 2 On-time (normal operation) V
IN
= 40V, R
ON
= 200 kΩ 655 ns
t
ON
- 3 On-time (current limit) V
IN
= 10V, R
ON
= 200 kΩ 1.13 µs
Shutdown threshold at RON/SD Voltage at RON/SD rising 0.4 0.8 1.2 V
Shutdown Threshold hysteresis Voltage at RON/SD falling 32 mV
Off Timer
t
OFF
Minimum Off-time 265 ns
Regulation and Over-Voltage Comparators (FB Pin)
V
REF
FB regulation threshold SS pin = steady state 2.445 2.50 2.550 V
FB over-voltage threshold 2.9 V
FB bias current 15 nA
Thermal Shutdown
T
SD
Thermal shutdown temperature Junction temperature rising 175 °C
Thermal shutdown hysteresis 20 °C
Thermal Resistance
θ
JA
Junction to Ambient
30 °C/W
0 LFPM Air Flow
(4)
θ
JC
Junction to Case
(4)
8 °C/W
(4) Value shown assumes a 4-layer PC board and 4 vias to conduct heat from beneath the package.
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