LT1766IGN#PBF Linear Technology, LT1766IGN#PBF Datasheet - Page 19

• Manufacturer Part Number: LT1766IGN#PBF
• Description: IC SW REG STP-DWN 200KHZ 16-SSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LT1766IGN#PBF

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.2 ~ 54 V
• Current - Output: 1.5A
• Frequency - Switching: 200kHz
• Voltage - Input: 5.5 ~ 60 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP
• Primary Input Voltage: 60V
• No. Of Outputs: 1
• Output Voltage: 15V
• Output Current: 1.5A
• No. Of Pins: 16
• Operating Temperature Range: -40°C To +125°C
• Msl: MSL 1 - Unlimited
• Rohs Compliant: Yes
• Dc To Dc Converter Type: Step Down
• Pin Count: 16
• Input Voltage: 60V
• Switching Freq: 216KHz
• Package Type: SSOP N
• Output Type: Adjustable
• Switching Regulator: Yes
• Mounting: Surface Mount
• Input Voltage (min): 5.5V
• Operating Temperature Classification: Automotive
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Compliant

APPLICATIONS INFORMATION
maximum rating. A ground plane should always be used
under the switcher circuitry to prevent interplane coupling
and overall noise.
The V
possible from the switch and boost nodes. The LT1766
pinout has been designed to aid in this. The ground for
these components should be separated from the switch
current path. Failure to do so will result in poor stability
or subharmonic like oscillation.
Board layout also has a signifi cant effect on thermal
resistance. Pins 1, 8, 9 and 16, GND, are a continuous
copper plate that runs under the LT1766 die. This is the
best thermal path for heat out of the package. Reducing
the thermal resistance from Pins 1, 8, 9 and 16 onto the
board will reduce die temperature and increase the power
capability of the LT1766. This is achieved by providing as
much copper area as possible around these pins. Add-
ing multiple solder fi lled feedthroughs under and around
these four corner pins to the ground plane will also help.
Similar treatment to the catch diode and coil terminations
C
and FB components should be kept as far away as
MINIMIZE LT1766
C3-D1 LOOP
GND
V
IN
GROUND PINS (4 CORNERS) FOR
GOOD THERMAL CONDUCTIVITY
PLACE FEEDTHROUGH AROUND
D1
C3
L1
1
2
3
4
5
6
7
8
Figure 6. Suggested Layout
GND
SW
V
BOOST
GND
C2
IN
LT1766
D2
BIAS
GND
GND
V
FB
C
16
15
14
13
12
11
10
9
will reduce any additional heating effects. For the FE pack-
age, the exposed pad (Pin 17) should be soldered to the
copper ground plane underneath the device.
PARASITIC RESONANCE
Resonance or ringing may sometimes be seen on the
switch node (see Figure 7). Very high frequency ringing
following switch rise time is caused by switch/diode/input
capacitor lead inductance and diode capacitance. Schottky
diodes have very high “Q” junction capacitance that can
ring for many cycles when excited at high frequency. If
total lead length for the input capacitor, diode and switch
path is 1 inch, the inductance will be approximately 25nH.
At switch off, this will produce a spike across the NPN
output device in addition to the input voltage. At higher
currents this spike can be in the order of 10V to 20V
or higher with a poor layout, potentially exceeding the
absolute max switch voltage. The path around switch,
catch diode and input capacitor must be kept as short as
possible to ensure reliable operation. When looking at this,
SHDN
SYNC
R1
C
FB
C1
GROUND PLANE
R
C
CONNECT TO
C
C
R2
C
F
KEEP FB AND V
AWAY FROM HIGH FREQUENCY,
HIGH CURRENT COMPONENTS
V
GND
KELVIN SENSE
OUT
V
OUT
1766 F06
LT1766/LT1766-5
FOR THE FE PACKAGE, THE
EXPOSED PAD (PIN 17) SHOULD
BE PROPERLY SOLDERED TO
THE GROUND PLANE.
NOTE: BOOST AND BIAS
COPPER TRACES ARE ON
A SEPARATE LAYER FROM
THE GROUND PLANE
C
COMPONENTS
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