Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2
Copyright
2000
Rev. 1.0c, 2005-03-08
WWW
.Microse
m
i
.CO
M
LX1684
Voltage-Mode PWM Controller
PRODUCTION DATA SHEET
TM
ABSOLUTE MAXI MUM RATI NGS ( NOTE 1)
Supply Voltage (VC1) ...................................................................................... 18V
Supply Voltage (VCC)........................................................................................ 7V
Input Voltage (CSP Pin) ................................................................................. 14V
Output Drive Peak Current Source (500ns) ................................................... 1.0A
Output Drive Peak Current Sink (500ns) ....................................................... 1.0A
Input Voltage (SS/ENABLE Pin) .......................................................... -0.3 to 6V
Operating Junction Temperature.................................................................. 150°C
Storage Temperature ................................................................... -65°C to +150°C
Peak Package Solder Reflow Temp. (40 second max. exposure) ...260°C (+0, -5)
Note: Exceeding these ratings could cause damage to the device. All voltages are with respect to
Ground. Currents are positive into, negative out of specified terminal.
PACKAGE PI N OUT
1
2
4
3
14
13
11
12
14-PIN SOIC
(T op View)
5
6
10
7
9
8
TDRV
N/C
V
C1
N/C
CS
N/C
V
CC
FB
N/C
SS
VCSP
GND
PG ND
BDRV
RoHS / Pb-free 100% Matte Tin Lead Finish
TH ERM A L DATA
D P
ACKAGE
THERMAL RESISTANCE
-JUNCTION TO AMBIENT,
θ
JA
165
°C/W
Junction Temperature Calculation: TJ = TA + (PD x θJA).
The θJA numbers are guidelines for the thermal performance of the device/pc-board
system. All of the above assume no ambient airflow.
FUNCTIONAL PIN DESCRIPTION
PIN NAME
DESCRIPTION
VFB
Voltage Feedback. A 1.25V reference is connected to a resistor divider to set desired output voltage.
SS
Soft-Start And Hiccup Capacitor Pin. During start up the voltage of this pin controls the output voltage. An
internal 22k
resistor and the external capacitor set the time constant for soft-startup. Soft-start does not begin
until the supply voltage exceeds the UVLO threshold. When over-current occurs, this capacitor is used for timing
hiccup. The PWM can be disabled by pulling the SS pin below 0.3V
VCSP
Positive Over-Current Threshold Input
GND
Analog ground for SS, FB, CS and VCC.
PGND
MOSFET driver power ground
TDRV
Gate Drive For Upper MOSFET.
BDRV
Gate Drive For Lower MOSFET.
VC1
Separate Supply For MOSFET Gate Drives. Connect to gate drive voltage.
CS
Over-Current Set. Connect resistor between CS pin and the source of the upper MOSFET to set current-limit
point.
VCC
IC Supply Voltage (nominal 5V).
PP
AA
CC
KK
AA
GG
EE
DD
AA
TT
AA