LM2716
Dual (Step-up and Step-down) PWM DC/DC Converter
General Description
The LM2716 is composed of two PWM DC/DC converters. A
buck (step-down) converter is used to generate a fixed out-
put voltage. A boost (step-up) converter is used to generate
an adjustable output voltage. Both converters feature low
R
DSON
(0.16
and 0.12) internal switches for maximum
efficiency. Operating frequency can be adjusted anywhere
between 300kHz and 600kHz allowing the use of small
external components. External soft-start pins for each en-
ables the user to tailor the soft-start times to a specific
application. Each converter may also be shut down indepen-
dently with its own shutdown pin. The LM2716 is available in
a low profile 24-lead TSSOP package.
Features
n
Fixed buck converter with a 1.8A, 0.16
, internal switch
n
Adjustable boost converter with a 3.6A, 0.12
, internal
switch
n
Adjustable boost output voltage up to 20V
n
Operating input voltage range of 4V to 20V
n
Input undervoltage protection
n
300kHz to 600kHz pin adjustable operating frequency
n
Over temperature protection
n
Small 24-Lead TSSOP package
n
Patented current limit circuitry
Applications
n
TFT-LCD Displays
n
Handheld Devices
n
Portable Applications
n
Cellular Phones/Digital Camers
Typical Application Circuit
20071201
July 2004
LM2716
Dual
(Step-up
and
Step-down)
PWM
DC/DC
Converter
2004 National Semiconductor Corporation
DS200712
www.national.com
Pin Description
Pin
Name
Function
1
PGND
Power ground. AGND and PGND pins must be connected together directly at the part.
2
FB1
Buck output voltage feedback input.
3
V
C1
Buck compensation network connection. Connected to the output of the voltage error
amplifier.
4
V
BG
Bandgap connection.
5
SS2
Boost soft start pin.
6
V
C2
Boost compensation network connection. Connected to the output of the voltage error
amplifier.
7
FB2
Boost output voltage feedback input.
8
AGND
Analog ground. AGND and PGND pins must be connected together directly at the part.
9
AGND
Analog ground. AGND and PGND pins must be connected together directly at the part.
10
PGND
Power ground. AGND and PGND pins must be connected together directly at the part.
11
PGND
Power ground. AGND and PGND pins must be connected together directly at the part.
12
PGND
Power ground. AGND and PGND pins must be connected together directly at the part.
13
SW2
Boost power switch input. Switch connected between SW2 pins and PGND pins. SW2
pins should be connected directly together at the device.
14
SW2
Boost power switch input. Switch connected between SW2 pins and PGND pins. SW2
pins should be connected directly together at the device.
15
SW2
Boost power switch input. Switch connected between SW2 pins and PGND pins. SW2
pins should be connected directly together at the device.
16
V
IN
Analog power input. V
IN
pins must be connected together directly at the DUT.
17
V
IN
Analog power input. V
IN
pins must be connected together directly at the DUT.
18
SHDN2
Shutdown pin for Boost converter. Active low.
19
FSLCT
Switching frequency select input. Use a resistor to set the frequency anywhere between
300kHz and 600kHz.
20
SS1
Buck soft start pin.
21
SHDN1
Shutdown pin for Buck converter. Active low.
22
CB1
Buck converter bootstrap capacitor connection.
23
V
IN
Analog power input. V
IN
pins must be connected together directly at the DUT.
24
SW1
Buck power switch input. Switch connected between V
IN
pins and SW1 pin.
LM2716
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Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
V
IN
-0.3V to 22V
SW1 Voltage
-0.3V to 22V
SW2 Voltage
-0.3V to 22V
FB1 Voltage
-0.3V to 7V
FB2 Voltage
-0.3V to 7V
V
C1
Voltage
1.75V
V
C1
2.25V
V
C2
Voltage
0.965V
V
C2
1.565V
SHDN1 Voltage
-0.3V to 7.5V
SHDN2 Voltage
-0.3V to 7.5V
SS1 Voltage
-0.3V to 2.1V
SS2 Voltage
-0.3V to 0.6V
FSLCT Voltage
AGND to 5V
CB1 Voltage
V
IN
+ 7V (V
IN
= V
SW
)
Maximum Junction Temperature
150C
Power Dissipation(Note 2)
Internally Limited
Lead Temperature
300C
Vapor Phase (60 sec.)
215C
Infrared (15 sec.)
220C
ESD Susceptibility (Note 3)
Human Body Model
2kV
Machine Model
200V
Operating Conditions
Operating Junction
Temperature Range
(Note 4)
-40C to +125C
Storage Temperature
-65C to +150C
Supply Voltage
4V to 20V
SW1 Voltage
20V
SW2 Voltage
20V
Electrical Characteristics
Specifications in standard type face are for T
J
= 25C and those with boldface type apply over the full Operating Tempera-
ture Range (T
J
= -40C to +125C) Unless otherwise specified. V
IN
= 5V and I
L
= 0A, unless otherwise specified.
Symbol
Parameter
Conditions
Min
(Note 4)
Typ
(Note 5)
Max
(Note 4)
Units
I
Q
Total Quiescent Current (both
switchers)
Not Switching
2.8
3.5
mA
Switching, switch open
4
4.5
mA
V
SHDN
= 0V
9
15
A
V
BG
Bandgap Voltage
1.235
1.26
1.285
V
I
CL1
(Note 6) Buck Switch Current Limit
95% Duty Cycle (Note 7)
1.8
A
I
CL2
(Note 6) Boost Switch Current Limit
95% Duty Cycle (Note 7)
3.6
A
I
FB1
Buck FB Pin Bias Current
(Note 8)
V
FB1
= 3.3V
65
75
A
I
FB2
Boost FB Pin Bias Current
(Note 8)
V
FB2
= 1.265V
27
55
nA
V
IN
Input Voltage Range
4
20
V
g
m1
Buck Error Amp
Transconductance
I = 20A
1200
mho
g
m2
Boost Error Amp
Transconductance
I = 5A
175
mho
A
V1
Buck Error Amp Voltage Gain
100
V/V
A
V2
Boost Error Amp Voltage
Gain
135
V/V
D
MAX
Maximum Duty Cycle
90
95
98
%
F
SW
Switching Frequency
R
F
= 47.5k
250
300
350
kHz
R
F
= 22.6k
500
600
700
kHz
I
SHDN1
Buck Shutdown Pin Current
0V
<
V
SHDN1
<
7.5V
-5
5
A
I
SHDN2
Boost Shutdown Pin Current
0V
<
V
SHDN2
<
7.5V
-5
5
A
I
L1
Buck Switch Leakage Current V
DS
= 20V
0.2
5
A
I
L2
Boost Switch Leakage
Current
V
DS
= 20V
0.2
3
A
R
DSON1
Buck Switch R
DSON
160
m
R
DSON2
Boost Switch R
DSON
120
m
LM2716
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