Datasheet
LTM4602
16
4602fa
Table 4. 3.3V Output
AIR FLOW (LFM) HEAT SINK θ
JA
(°C/W)
0 None 15.2
200 None 14.6
400 None 13.4
0 BGA Heat Sink 13.9
200 BGA Heat Sink 11.1
400 BGA Heat Sink 10.5
Table 3. 1.5V Output
AIR FLOW (LFM) HEAT SINK θ
JA
(°C/W)
0 None 15.2
200 None 14
400 None 12
0 BGA Heat Sink 13.9
200 BGA Heat Sink 11.3
400 BGA Heat Sink 10.25
Layout Checklist/Example
The high integration of the LTM4602 makes the PCB board
layout very simple and easy. However, to optimize its electri-
cal and thermal performance, some layout considerations
are still necessary.
• Use large PCB copper areas for high current path,
including V
IN
, PGND and V
OUT
. It helps to minimize the
PCB conduction loss and thermal stress.
• Place high frequency ceramic input and output capaci-
tors next to the V
IN
, PGND and V
OUT
pins to minimize
high frequency noise.
• Place a dedicated power ground layer underneath
the unit.
• To minimize the via conduction loss and reduce module
thermal stress, use multiple vias for interconnection
between top layer and other power layers.
• Do not put vias directly on pads unless they are capped.
• Use a separated SGND ground copper area for com-
ponents connected to signal pins. Connect the SGND
to PGND underneath the unit.
Figure 18 gives a good example of the recommended
layout.
LTM4602 Frequency Adjustment
The LTM4602 is designed to typically operate at 850kHz
across most input and output conditions. The control ar-
chitecture is constant on time valley mode current control.
The f
ADJ
pin is typically left open or decoupled with an
optional 1000pF capacitor. The switching frequency has
been optimized to maintain constant output ripple over the
operating conditions. The equations for setting the operat-
ing frequency are set around a programmable constant on
time. This on time is developed by a programmable current
into an on board 10pF capacitor that establishes a ramp
that is compared to a voltage threshold equal to the output
voltage up to a 2.4V clamp. This I
ON
current is equal to:
I
ON
= (V
IN
– 0.7V)/110k, with the 110k onboard resistor
Figure 16. 12V to 3.3V, No Heat Sink
Figure 17. 12V to 3.3V, BGA Heat Sink
TEMPERATURE (°C)
50
5
6
7
90
4602 F16
4
3
60 70 80 100
2
1
0
CURRENT (A)
0LFM
200LFM
400LFM
TEMPERATURE (°C)
50
5
6
7
90
4602 F16
4
3
60 70 80 100
2
1
0
CURRENT (A)
0LFM
200LFM
400LFM
APPLICATIONS INFORMATION