LTC3829EFE#PBF Linear Technology, LTC3829EFE#PBF Datasheet - Page 32

• Manufacturer Part Number: LTC3829EFE#PBF
• Description: IC BUCK SYNC ADJ 38TSSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3829EFE#PBF

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.6 ~ 5 V
• Frequency - Switching: 250kHz ~ 770kHz
• Voltage - Input: 4.5 ~ 38 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 38-TSSOP Exposed Pad, 38-eTSSOP, 38-HTSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Power - Output: -

LTC3829
applicaTions inForMaTion
Minimum On-Time Considerations
Minimum on-time, t
that the LTC3829 is capable of turning on the top MOSFET.
It is determined by internal timing delays and the gate
charge required to turn on the top MOSFET. Low duty
cycle applications may approach this minimum on-time
limit and care should be taken to ensure that:
If the duty cycle falls below what can be accommodated
by the minimum on-time, the controller will begin to skip
cycles. The output voltage will continue to be regulated,

t
ON MIN
(
)
<
V
V
IN
OUT
( )
f
ON(MIN)
, is the smallest time duration
OSCILLATOR
EXTERNAL
Figure 16. Phase-Locked Loop Block Diagram
900
800
700
600
500
400
300
200
100
Figure 15. Relationship Between Oscillator
Frequency and Voltage at the FREQ Pin
0
PLLIN
0
0.5
FREQUENCY
DETECTOR
DIGITAL
FREQ PIN VOLTAGE (V)
PHASE/
1
SYNC
1.5
but the ripple voltage and current will increase. The
minimum on-time for the LTC3829 is approximately 90ns,
with reasonably good PCB layout, minimum 30% induc-
tor current ripple and at least 10mV ripple on the current
sense signal. The minimum on-time can be affected by
PCB switching noise in the voltage and current loop. As
the peak sense voltage decreases the minimum on-time
gradually increases to 130ns. This is of particular concern
in forced continuous applications with low ripple current
at light loads. If the duty cycle drops below the minimum
on-time limit in this situation, a significant amount of cycle
skipping can occur with correspondingly larger current
and voltage ripple.
2.4V
5V
2
10µA
38501 F15
2.5
FREQ
R
SET
VCO
3829 F16
3829f