Datasheet
FB
V
IN
V
CC
SW
RTN
ON TIMER
DRIVER
V
IN
BST
LEVEL
SHIFT
SD /
R
ON
2.5V
THERMAL
SHUTDOWN
0.50A
BUCK
SWITCH
CURRENT
SENSE
COMPLETE
R
CL
START
R
CL
COMPLETE
START
Ron
L1
C4
9.5 -95V
Input
C3
LM5008
UVLO
FB
UVLO
REGULATION
COMPARATOR
OVER-VOLTAGE
COMPARATOR
2.875V
SD
SD
COMPLETE
START
300 ns MIN OFF
TIMER
8
6
5
3
4
1
2
7
7V SERIES
REGULATOR
CURRENT LIMIT
OFF TIMER
SHUTDOWN
D1
Q
CLR
Q
SET
S
R
+
-
+
-
+
-
C1
R
ON
R
CL
R2
R3
V
OUT2
V
OUT1
R1
C5
C2
LM5008
SNVS280G –APRIL 2004–REVISED MARCH 2013
www.ti.com
Typical Application Circuit and Block Diagram
Figure 2.
Pin Functions
Table 1. Pin Descriptions
Pin Name Description Application Information
1 SW Switching node Power switching node. Connect to the output inductor, re-circulating
diode, and bootstrap capacitor.
2 BST Boost pin (bootstrap capacitor input) An external capacitor is required between the BST and the SW pins.
A 0.01µF ceramic capacitor is recommended. An internal diode
charges the capacitor from V
CC
.
3 R
CL
Current limit OFF time set pin A resistor between this pin and RTN sets the off-time when current
Toff = 10
-5
/ (0.285 + (FB / 6.35 x 10
− 6
x R
CL
)) limit is detected. The off-time is preset to 35µs if FB = 0V.
4 RTN Ground pin Ground for the entire circuit.
5 FB Feedback input from regulated output This pin is connected to the inverting input of the internal regulation
comparator. The regulation threshold is 2.5V.
6 R
ON
/SD On time set pin A resistor between this pin and V
IN
sets the switch on time as a
Ton = 1.25 x 10
-10
R
ON
/ V
IN
function of V
IN
. The minimum recommended on time is 400ns at the
maximum input voltage. This pin can be used for remote shutdown.
7 V
CC
Output from the internal high voltage series pass If an auxiliary voltage is available to raise the voltage on this pin,
regulator. Regulated at 7.0 V. above the regulation set point (7V), the internal series pass
regulator will shutdown, reducing the IC power dissipation. Do not
exceed 14V. This voltage provides gate drive power for the internal
Buck switch. An internal diode is provided between this pin and the
BST pin. A local 0.1µF decoupling capacitor is recommended.
Series pass regulator is current limited to 10mA.
8 V
IN
Input voltage Recommended operating range: 9.5V to 95V.
EP Exposed Pad The exposed pad has no electrical contact. Connect to system
ground plane for reduced thermal resistance.
2 Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated
Product Folder Links: LM5008