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1
LTC1433/LTC1434
450mA, Low Noise
Current Mode Step-Down
DC/DC Converters
s
Cellular Telephones
s
Portable Instruments
s
Wireless Modems
s
RF Communications
s
Distributed Power Systems
s
Scanners
s
Battery-Powered Equipment
DESCRIPTIO
N
U
s
High Efficiency: Up to 93%
s
Constant Frequency Adaptive Power
TM
Operation
s
Input Voltage Range: 3V to 13.5V
s
Internal 0.6
Power Switch (V
IN
= 10V)
s
Low Dropout Operation: 100% Duty Cycle
s
Low-Battery Detector
s
Internal Power-On Reset Timer
s
Current Mode Operation for Excellent Line and Load
Transient Response
s
Low Quiescent Current: 470
A
s
Shutdown Mode Draws Only 15
A Supply Current
s
1% Reference Accuracy
s
Available in 16- and 20-Lead Narrow SSOP
FEATURES
The LTC
1433/LTC1434 are monolithic pulse width modu-
lated step-down DC/DC converters. By utilizing current
mode switching techniques, they provide excellent AC and
DC load and line regulation. Both devices operate at a fixed
frequency with the LTC1434 phase-lockable to an external
clock signal.
Both devices incorporate two internal P-channel power
MOSFETs with a parallel combined resistance of 0.6
(at
a supply of 10V). The Adaptive Power output stage selec-
tively drives one or both of the switches at frequencies up
to 700kHz to reduce switching losses and maintain high
efficiencies at low output currents.
The LTC1433/LTC1434 are capable of supplying up to
450mA of output current and boasts a
2.4% output
voltage accuracy. An internal low-battery detector has the
same level of accuracy as the output voltage. A power-on
reset timer (POR) is included which generates a signal
delayed by 65536/f
CLK
(300ms typ) after the output is
within 5% of the regulated output voltage.
Ideal for current sensitive applications, the devices draw
only 470
A of quiescent current. In shutdown the devices
draw a mere 15
A. To further maximize the life of the
battery source, the internal P-channel MOSFET switch is
turned on continuously in dropout.
APPLICATIO
N
S
U
, LTC and LT are registered trademarks of Linear Technology Corporation.
Adaptive Power is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
N
U
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
SSW
NC
BSW
NC
SGND
RUN/SS
LBO
LBI
PWRV
IN
SV
IN
C
OSC
POR
I
TH
V
OSENSE
V
PROG
LTC1433
PGND
68
F**
20V
0.1
F
0.1
F
100
F*
10V
D1: MOTOROLA MBRS130LT3
L1: COILCRAFT D03316-104
V
OUT
3.3V
D1
L1
100
H
POWER-ON
RESET
V
IN
3.5V TO 12V
680pF
5.1k
10k
6800pF
47pF
1433/34 F01
* AVX TPSD107M010R0100
** AVX TPSE686M020R0150
+
+
Figure 1. High Efficiency Step-Down Converter
LOAD CURRENT (A)
0.001
60
EFFICIENCY (%)
70
80
0.01
0.1
1
1433/34 TA01
50
40
100
90
V
IN
= 5V
V
IN
= 12V
V
IN
= 9V
LTC1433 Efficiency for
V
OUT
= 3.3V
2
LTC1433/LTC1434
A
U
G
W
A
W
U
W
A
R
BSOLUTE
XI
TI
S
(Voltages Referred to PGND Pin)
Input Supply Voltage (PWRV
IN
, SV
IN
) ... 13.5V to 0.3V
DC Small Switch Current (SSW) ......................... 100mA
Peak Small Switch Current (SSW) ..................... 300mA
Small Switch Voltage
(SSW) ................................ (V
IN
+ 0.3V) to (V
IN
13.5V)
DC Large Switch Current (BSW) ....................... 600mA
Peak Large Switch Current (BSW) .......................... 1.2A
Large Switch Voltage
(BSW) ................................ (V
IN
+ 0.3V) to (V
IN
13.5V)
PLLIN, PLL LPF, I
TH
, C
OSC
........................ 2.7V to 0.3V
POR, LBO .................................................. 12V to 0.3V
LBI, V
OSENSE
.............................................. 10V to 0.3V
RUN/SS, V
PROG
Voltages
V
IN
11.7V ...........................................12V to 0.3V
V
IN
< 11.7V ............................... (V
IN
+ 0.3V) to 0.3V
Commercial Temperature Range
LTC1433C/LTC1434C .............................. 0
C to 70
C
Extended Commercial Operating Temperature
Range (Note 2) ....................................... 40
C to 85
C
Industrial Temperature Range (Note 3)
LTC1433I/LTC1434I ........................... 40
C to 85
C
Junction Temperature (Note 4)............................. 125
C
Storage Temperature Range ................. 65
C to 150
C
Lead Temperature (Soldering, 10 sec).................. 300
C
(Note 1)
W
U
U
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
ORDER PART
NUMBER
LTC1433CGN
LTC1433IGN
LTC1434CGN
LTC1434IGN
T
JMAX
= 125
C,
JA
= 150
C/ W
T
JMAX
= 125
C,
JA
= 150
C/ W
1
2
3
4
5
6
7
8
TOP VIEW
GN PACKAGE
16-LEAD PLASTIC SSOP
16
15
14
13
12
11
10
9
SSW
NC
BSW
NC
SGND
RUN/SS
LBO
LBI
PWRV
IN
PGND
SV
IN
C
OSC
POR
I
TH
V
OSENSE
V
PROG
Consult factory for Military grade parts.
1
2
3
4
5
6
7
8
9
10
TOP VIEW
GN PACKAGE
20-LEAD PLASTIC SSOP
20
19
18
17
16
15
14
13
12
11
NC
SSW
NC
BSW
SGND
NC
RUN/SS
NC
LBO
LBI
PWRV
IN
PGND
SV
IN
PLLIN
PLL LPF
C
OSC
POR
I
TH
V
OSENSE
V
PROG
ELECTRICAL CHARACTERISTICS
T
A
= 25
C, V
IN
= 10V, V
RUN/SS
= 5V, unless otherwise noted. (Notes 2, 3)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Main Control Loop
I
IN
V
OSENSE
Feedback Current
V
PROG
Pin Open (Note 5)
10
50
nA
V
OSENSE
Regulated Output Voltage
(Note 5)
1.19V (Adjustable) Selected
V
PROG
Pin Open
q
1.178
1.190
1.202
V
3.3V Selected
V
PROG
= 0V
q
3.220
3.300
3.380
V
5V Selected
V
PROG
= V
IN
q
4.880
5.000
5.120
V
V
OVL
Output Overvoltage Lockout
V
PROG
Pin Open
1.24
1.28
1.32
V
V
OSENSE
Reference Voltage Line Regulation
V
IN
= 3.6V to 13V (Note 5), V
PROG
Pin Open
0.002
0.01
%/V
V
LOADREG
Output Voltage Load Regulation
I
TH
Sinking 5
A (Note 5)
q
0.5
0.8
%
I
TH
Sourcing 5
A (Note 5)
q
0.5
0.8
%
3
LTC1433/LTC1434
ELECTRICAL CHARACTERISTICS
T
A
= 25
C, V
IN
= 10V, V
RUN/SS
= 5V, unless otherwise noted.
The
q
denotes specifications which apply over the specified temperature
range.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: C-grade device specifications are guaranteed over the 0
C to 70
C
temperature range. In addition, C-grade device specifications are assured
over the 40
C to 85
C temperature range by design or correlation, but
are not production tested.
Note 3: I-grade device specifications are guaranteed over the 40
C to
85
C temperature range by design, testing or correlation.
Note 4: T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
LTC1433/LTC1434: T
J
= T
A
+ (P
D
)(150
C/W)
Note 5: The LTC1433/LTC1434 are tested in a feedback loop which servos
V
OSENSE
to the feedback point for the error amplifier (V
ITH
= 1.19V).
Note 6: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
Note 7: Oscillator frequency is tested by measuring the C
OSC
charge and
discharge currents and applying the formula:
f
OSC
(kHz) =
+
1
8.4(10
8
)
C
OSC
(pF) + 11
(
)
1
I
CHG
(
)
1
I
DIS
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
PROG
V
PROG
Input Current
0.5V > V
PROG
4
10
A
V
IN
0.5V < V
PROG
< V
IN
4
10
A
Main Control Loop
I
Q
Input DC Supply Current
(Note 6)
Normal Mode
3.6V < V
IN
< 13V
470
A
Shutdown, Reference Alive
V
RUN/SS
= 0V, 3.6V < V
IN
< 13V, LBI > 0.9V
35
70
A
Complete Shutdown
V
RUN/SS
= 0V, 3.6V < V
IN
< 13V, LBI
0.48V
15
30
A
V
RUN/SS
RUN/SS Threshold
q
0.8
1.3
2
V
I
RUN/SS
Soft Start Current Source
V
RUN/SS
= 0V
1.2
3
4.5
A
Oscillator and Phase-Locked Loop
f
OSC
Oscillator Frequency
C
OSC
= 100pF (Note 7)
112
125
142
kHz
V
CO
High
V
PLL LPF
= 2.4V
200
240
kHz
R
PLLIN
PLL Input Resistance
50
k
I
PLL LPF
Phase Detector Output Current
Sinking Capability
f
PLLIN
< f
OSC
10
15
20
A
Sourcing Capability
f
PLLIN
> f
OSC
10
15
20
A
Power-On Reset
V
SATPOR
POR Saturation Voltage
I
POR
= 1.6mA, V
OSENSE
= 1V, V
PROG
Open
0.6
1.0
V
I
LPOR
POR Leakage
V
POR
= 10V, V
OSENSE
= 1.2V, V
PROG
Open
0.2
1.0
A
V
TRPOR
POR Trip Voltage from Regulated
V
PROG
Pin Open, V
OSENSE
Ramping Negative
11
7.5
4
%
Output
t
DPOR
POR Delay
V
PROG
Pin Open
65536
Cycles
Low-Battery Comparator
V
SATLBO
LBO Saturation Voltage
I
LBO
= 1.6mA, V
LBI
= 1.1V
0.6
1.0
V
I
LLBO
LBO Leakage
V
LBO
= 10V, V
LBI
= 1.4V
0.01
1.0
A
V
TRLBI
LBI Trip Voltage
High to Low Transition on LBO
1.16
1.19
1.22
V
V
HYSTLB
Low-Battery Comparator Hysteresis
40
mV
V
SDLB
Low-Battery Shutdown Trip Point
0.74
V
I
INLBI
LBI Input Current
V
LBI
= 1.19V
1
50
nA
P-Channel Power FETs Characteristics
R
SMFET
R
DS(ON)
of Small FET
I
SSW
= 15mA
3.3
4.1
R
BIGFET
R
DS(ON)
of Big FET
I
BSW
= 150mA
0.8
1.2
I
LSSW
Small FET Leakage
V
RUN/SS
= 0V
q
7
1000
nA
I
LBSW
Big FET Leakage
V
RUN/SS
= 0V
q
5
1000
nA
4
LTC1433/LTC1434
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
LOAD CURRENT (A)
0.001
60
EFFICIENCY (%)
70
80
0.01
0.1
1
1433/34 G01
50
40
100
90
V
IN
= 5V
V
IN
= 12V
V
IN
= 3.6V
V
OUT
= 3.3V
L = 22
H
C
SOC
= 47pF
Efficiency of Figure 1 for L = 22
H
SUPPLY VOLTAGE (V)
3.2
OUTPUT VOLTAGE (V)
3.0
3.2
3.4
4.8
1433/34 G03
2.8
2.6
2.9
3.1
3.3
2.7
2.5
2.4
3.6
4.0
4.4
3.4
5.0
3.8
4.2
4.6
5.2
V
PROG
= 0V
L = 20
H
C
OSC
= 50pF
I
OUT
300mA
I
OUT
400mA
I
OUT
500mA
Dropout Characteristics at Different
Load Currents (V
OUT
= 3.3V)
SUPPLY VOLTAGE (V)
3
360
SUPPLY CURRENT (
A)
380
400
420
440
5
7
9
11
1433/34 G02
460
480
4
6
8
10
Supply Current vs Supply Voltage
Dropout Characteristics at Different
Load Currents (V
OUT
= 5V)
Maximum Output Current
vs Input Supply
SUPPLY VOLTAGE (V)
4.6
4.8
5.0
5.2
5.4
5.6
5.8
6.0
6.2
OUTPUT VOLTAGE (V)
4.7
4.8
4.9
1433/34 G04
4.6
4.5
4.2
4.3
4.4
5.1
5.0
I
OUT
200mA
I
OUT
400mA
I
OUT
300mA
V
PROG
= V
IN
L = 20
H
C
OSC
= 50pF
SUPPLY VOLTAGE (V)
3
MAXIMUM OUTPUT CURRENT (mA)
500
600
700
800
11
1433/34 G05
400
300
200
5
7
9
13
V
OUT
3.3V
V
OUT
5V
L = 22
H
C
OSC
= 50pF
Reference Voltage
vs Temperature
TEMPERATURE (
C)
45
REFERENCE VOLTAGE (V)
1.186
1.194
115
1433/34 G06
1.178
1.170
5
35
75
25
15
55
95
1.202
1.182
1.190
1.174
1.198
SUPPLY VOLTAGE (V)
3
R
DS(ON)
OF SMALL FET (
)
6
8
11
1433/34 G07
4
2
5
7
3
1
0
5
7
9
4
12
6
8
10
13
T
A
= 25
C
T
A
= 70
C
T
A
= 0
C
Switch Resistance of Small FET
Switch Leakage Current
vs Temperature
TEMPERATURE (
C)
0
40
50
70
60
100
1433/34 G09
30
20
20
40
80
120
140
10
0
60
160
200
280
120
80
40
0
240
SWITCH LEAKAGE AT SSW PIN (nA)
SWITCH LEAKAGE AT BSW PIN (nA)
V
IN
= 13.5V
SSW PIN
BSW PIN
Switch Resistance of Big FET
SUPPLY VOLTAGE (V)
3
R
DS(ON)
OF BIG FET (
)
1.2
1.6
2.0
11
1433/34 G08
0.8
0.4
0
1.4
1.8
1.0
0.6
0.2
5
7
9
4
12
6
8
10
13
T
A
= 70
C
T
A
= 0
C
T
A
= 25
C
5
LTC1433/LTC1434
PI
N
FU
N
CTIO
N
S
U
U
U
SSW (Pin 1/Pin 2): Drain of the Small P-Channel MOSFET
Switch.
BSW (Pin 3/Pin 4): Drain of the Large P-Channel MOSFET
Switch.
SGND (Pin 5): Small-Signal Ground. Must be routed
separately from other grounds to the () terminal of C
OUT
.
RUN/SS (Pin 6/Pin 7): Combination of Soft Start and Run
Control Inputs. A capacitor to ground at this pin sets the
ramp time to full current output. The time is approxi-
mately 0.5s/
F. Forcing this pin below 1.3V causes all
circuitry to be shut down except the low-battery com-
parator. For input voltages above 6V this pin is clamped by
a 6V Zener (see Functional Diagram). Applying voltages
greater than 6V to this pin will cause additional current to
flow into this pin.
LBO (Pin 7/Pin 9): Open-Drain Output of an N-Channel
Pull-Down. This pin will sink current when LBI goes below
1.19V.
LBI (Pin 8/Pin 10): The (+) Input of the Low-Battery
Voltage Comparator. The () input is connected to the
1.19V reference. When LBI is grounded along with RUN/
SS, this comparator will shut down along with the rest of
the control circuitry. LBO will go to high impedance.
V
PROG
(Pin 9/Pin 11): The voltage at this pin selects the
output voltage. When V
PROG
= 0V or V
PROG
= V
IN
, the
output is set to 3.3V and 5V respectively, with V
OSENSE
connected to the output. Leaving V
PROG
open (DC) allows
the output voltage to be set by an external resistive divider.
V
OSENSE
is then connected to the common node of the
resistive divider.
V
OSENSE
(Pin 10/Pin 12): This pin receives the feedback
voltage either from the output or from an external resistive
divider across the output. The V
PROG
pin determines at
which point V
OSENSE
must be connected.
V
PROG
= 0V
V
OUT
= 3.3V
V
PROG =
V
IN
V
OUT
= 5V
V
PROG
= Open (DC)
V
OUT
= Adjustable
I
TH
(Pin 11/Pin 13): Error Amplifier Compensation Point.
The current comparator threshold increases with this
control voltage. Nominal voltage range for this pin is 0V
to 2.4V.
POR (Pin 12/Pin 14): Open-Drain Output of an N-Chan-
nel Pull-Down. This pin sinks current when the output
voltage is 7.5% out of regulation. When the output rises
to 5% of its regulated value, the pin goes into high
impedance after 2
16
(65536) oscillator cycles. The POR
output is asserted when the device is in shutdown,
independent of V
OUT
.
C
OSC
(Pin 13/Pin 15): External capacitor connects be-
tween this pin and ground to set the operating frequency.
PLL LPF (Pin 16 LTC1434): Output of the Phase Detector
and Control Input of the Oscillator. Normally a series RC
lowpass network is connected from this pin to ground. Tie
this pin to SGND in applications which do not use the
phase-locked loop. Can be driven by a 0V to 2.4V logic
signal for a frequency shifting option.
PLLIN (Pin 17 LTC1434): External Synchronizing Input to
the Phase Detector. This pin is internally terminated to
SGND with 50k
. Tie this pin to SGND in applications
which do not use the phase-locked loop.
SV
IN
(Pin 14/Pin 18): Main Supply for All the Control
Circuitry.
PGND (Pin 15/Pin 19): Switch Driver Ground. Connects to
the () terminal of C
IN
. Anode of the Schottky diode must
be connected close to this pin.
PWRV
IN
(Pin 16/Pin 20): Supply for the Internal Power
MOSFETs and Switch Drivers. Must decouple this pin
properly to ground.
NC (Pins 2, 4,/Pins 1, 3, 6, 8): No Connection.
(LTC1433/LTC1434)
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