lm27241 National Semiconductor Corporation, lm27241 Datasheet - Page 7

• Manufacturer Part Number: lm27241
• Description: Synchronous Buck Regulator Controller For Mobile Systems
• Manufacturer: National Semiconductor Corporation

I
V
V
Oscillator
F
V
V
∆F
∆F
V
System
t
D
Gate Drivers
R
R
R
R
t
ILIM
ON_MIN
DEAD
Electrical Characteristics
OSC
Specifications with standard typeface are for T
ture range. VDD = V5 = 5V, V
Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.
ILIM_TH
SW_ZERO
RAMP
VALLEY
FREQ_VIN
MAX
HDRV_SOURCE
HDRV_SINK
LDRV_SOURCE
LDRV_SINK
Note 1: Absolute maximum ratings indicate limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the
device is guaranteed. For guaranteed performance limits and associated test conditions, see the Electrical Characteristics table.
Note 2: PGND and SGND are all electrically connected together on the PCB.
Note 3: The maximum allowable power dissipation is calculated by using P
ambient temperature, and θ
from using 125˚C, 25˚C, and 118˚C/W for T
TSSOP package. The θ
ambient temperatures. For detailed information on soldering plastic TSSOP package, refer to http://www.national.com/packaging/.
Note 4: ESD is applied by the human body model, which is a 100pF capacitor discharged through a 1.5 kΩ resistor into each pin.
Note 5: R
Note 6: If the LM27241 starts up with a pre-charged soft start capacitor, it will first discharge the capacitor to V
process.
Note 7: Typical numbers are at 25˚C and represent the most likely norm.
OSC_VIN
OSC_VDD
Symbol
FADJ
is the frequency adjust resistor between FREQ pin and Ground.
JA
value above represents the worst-case condition with no heat sinking. Heat sinking will permit more power to be dissipated at higher
JA
ILIM Pin Current (sourcing)
I
Zero-cross Threshold (SW
Pin)
PWM Frequency
PWM Ramp Peak-to-peak
Amplitude
PWM Ramp Valley
Frequency Change with
VIN
Frequency Change with
VDD
FREQ Pin Voltage vs. VIN
Minimum ON Time
Maximum Duty Cycle
HDRV Source Impedance
HDRV Sink Impedance
LDRV Source Impedance
LDRV Sink Impedance
Cross-conduction
Protection Delay
(deadtime)
is the junction-to-ambient thermal resistance of the specified package. The 0.75W rating of the TSSOP-20 package for example results
ILIM
Threshold Voltage
SGND
Parameter
JMAX
= V
, T
A
PGND
, and θ
(Continued)
= 0V, VIN = 15V, V
JA
J
respectively. The rated power dissipation should be derated by 10mW/˚C above 25˚C ambient for the
= 25˚C, and those with boldface apply over full Operating Junction Tempera-
V
LDRV goes low
R
R
R
VIN = 15V
VIN = 24V
VIN = 5.5V to 24V
VDD = 4.5V to 5.5V
V
VIN = 5.5V
VIN = 15V
VIN = 28V, VDD= 4.5V
HDRV Pin Current
(sourcing)= 1.2A
HDRV Pin Current (sinking)
= 1A
LDRV Pin Current (sourcing)
= 1.2A
LDRV Pin Current (sinking)
= 2A
HDRV Falling to LDRV
Rising
LDRV Falling to HDRV
Rising
ILIM
FPWM
FADJ
FADJ
FADJ
Dmax
= 0V
= 22.1kΩ
= 12.4kΩ
= 30.9kΩ
= 3V
Conditions
= (T
7
EN
JMAX
= 3V, R
- T
A
) /θ
FADJ
JA
, where T
= 22.1K unless otherwise stated (Note 5).
JMAX
Min
255
-10
46
60
40
22
SS_RESET
is the maximum junction temperature, T
(Note 7)
Typical
and then begin the normal Soft-start
0.105
2.95
-2.2
300
500
200
1.6
0.8
62
±
±
30
75
50
28
40
70
0
7
2
7
1
1
2
Max
345
76
10
www.national.com
Units
A
kHz
V/V
mV
mV
µA
ns
ns
%
%
%
%
%
Ω
Ω
Ω
Ω
V
V
is the