LT3689EMSE-5#PBF Linear Technology, LT3689EMSE-5#PBF Datasheet - Page 27

• Manufacturer Part Number: LT3689EMSE-5#PBF
• Description: IC BUCK 5V 0.7A 16MSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LT3689EMSE-5#PBF

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 5V
• Current - Output: 700mA
• Frequency - Switching: 350kHz ~ 2.2MHz
• Voltage - Input: 3.6 ~ 36 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-MSOP Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

APPLICATIONS INFORMATION
as possible. Finally, keep the FB node small so that the
ground traces will shield them from the SW and BOOST
nodes. The Exposed Pad on the bottom of the package
must be soldered to ground so that the pad acts as a heat
sink. To keep thermal resistance low, extend the ground
plane as much as possible, and add thermal vias under
and near the LT3689 to additional ground planes within
the circuit board and on the bottom side.
High Temperature Considerations
The PCB must provide heat sinking to keep the LT3689
cool. The Exposed Pad on the bottom of the package
must be soldered to a ground plane. This ground should
be tied to large copper layers below with thermal vias;
these layers will spread the heat dissipated by the LT3689.
Placing additional vias can reduce thermal resistance
further. Because of the large output current capability of
the LT3689, it is possible to dissipate enough heat to raise
the junction temperature beyond the absolute maximum
of 125°C (150°C for H-grade). When operating at high
ambient temperatures, the maximum load current should
TYPICAL APPLICATIONS
RESET
µP
I/O
I/O
6.3V TO 36V
TRANSIENT
L1: CDR125NP-12MC
D1: MBRM140
C1, C2, C3: X7R or X5R
TO 60V
WATCHDOG_DEFEAT
C6
10nF
t
WDU
WINDOW TIMEOUT
V
IN
= 182ms
C1
1µF
C5
68nF
t
RST
5V Step-Down Converter
= 157ms
W/T
WDE
WDI
WDO
RST
C
C
WDT
POR
V
IN
LT3689
GND
be derated as the ambient temperature approaches 125°C
(150°C for H-grade). A board measuring 5cm × 7.5cm with
a top layer layout similar to Figure 15 was evaluated in
still air at 3.3V
load, the temperature reached approximately 12°C above
ambient for input voltages equal to 12V and 24V. Power
dissipation within the LT3689 can be estimated by calculat-
ing the total power loss from an efficiency measurement
and subtracting the catch diode loss. The die temperature
is calculated by multiplying the LT3689 power dissipation
by the thermal resistance from junction-to-ambient.
Other Linear Technology Publications
Application Notes 19, 35 and 44 contain more detailed
descriptions and design information for buck regulators
and other switching regulators. The LT1376 data sheet
has a more extensive discussion of output ripple, loop
compensation and stability testing. Design Note 318
shows how to generate a bipolar output supply using a
buck regulator.
EN/UVLO
f
SW
SYNC
= 1MHz
OUT
BST
SW
DA
RT
FB
D1
OUT
C2
0.1µF
R
12.7k
T
, 700kHz switching frequency. At 700mA
5.6pF
C4
R2
102k
3689 TA02
12µH
L1
LT3689/LT3689-5
536k
R1
C3
10µF
5V
700mA
27
3689fd