LTC3832/LTC3832-1
High Power Step-Down
Synchronous DC/DC Controllers
for Low Voltage Operation
FEATURES
s
s
DESCRIPTIO
s
s
s
s
s
s
s
s
s
s
s
s
s
V
OUT
as Low as 0.6V
High Power Switching Regulator Controller
for 3.3V-5V to 0.6V-3.xV Step-Down Applications
No Current Sense Resistor Required
Low Input Supply Voltage Range: 3V to 8V
Maximum Duty Cycle > 91% Over Temperature
All N-Channel External MOSFETs
Excellent Output Regulation:
±1%
Over Line, Load
and Temperature Variations
High Efficiency: Over 95% Possible
Adjustable or Fixed 2.5V Output (LTC3832)
Programmable Fixed Frequency Operation: 100kHz to
500kHz
External Clock Synchronization
Soft-Start
Low Shutdown Current: <10µA
Overtemperature Protection
Available in SO-8 and SSOP-16 Packages
The LTC
®
3832/LTC3832-1 are high power, high effi-
ciency switching regulator controllers optimized for
3.3V-5V to 0.6V-3.xV step-down applications. A preci-
sion internal reference and feedback system provide
±1%
output regulation over temperature, load current
and line voltage variations. The LTC3832/LTC3832-1 use
a synchronous switching architecture with N-channel
MOSFETs. Additionally, the chip senses output current
through the drain-source resistance of the upper
N-channel MOSFET, providing an adjustable current limit
without a current sense resistor.
The LTC3832/LTC3832-1 operate with an input supply
voltage as low as 3V and with a maximum duty cycle of
>91% over temperature. They include a fixed frequency
PWM oscillator for low output ripple operation. The 300kHz
free-running clock frequency can be externally adjusted or
synchronized with an external signal from 100kHz to 500kHz.
In shutdown mode, the LTC3832 supply current drops to
<10µA. The LTC3832-1 is the SO-8 version without current
limit, frequency adjustment and shutdown functions.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s
s
s
s
CPU Power Supplies
Multiple Logic Supply Generator
Distributed Power Applications
High Efficiency Power Conversion
TYPICAL APPLICATIO
4.7µF
5.1Ω
0.1µF
0.01µF
15k
GND
6.49k
FB
4.32k
680pF
G2
PV
CC1
LTC3832-1
SS V
CC
/PV
CC2
COMP
G1
V
IN
3V TO 7V
100
+
MBR0520T1
90
80
70
60
50
V
IN
= 3.3V
40
0
1
2
Si9426DY
0.1µF
L1
3.2µH
V
OUT
1V
9A
Si9426DY
+
C
OUT
270µF
2V
3832 F01
L1: SUMIDA CDEP105-3R2MC-88
C
OUT
: PANASONIC EEFUEOD271R
EFFICIENCY (%)
Figure 1. High Efficiency 3.3V to 1V Power Converter
U
Efficiency
V
OUT
= 2.5V
V
OUT
= 1V
3 4 5 6 7
LOAD CURRENT (A)
8
9
10
3832 F01b
U
U
sn3832 3832fs
1
LTC3832/LTC3832-1
ABSOLUTE
AXI U
RATI GS
Supply Voltage
V
CC
....................................................................... 9V
PV
CC1,2
................................................................ 14V
Input Voltage
I
FB
, I
MAX
............................................... – 0.3V to 14V
SENSE
+
, SENSE
–
, FB,
SHDN, FREQSET ....................... – 0.3V to V
CC
+ 0.3V
PACKAGE/ORDER I FOR ATIO
TOP VIEW
G1
PV
CC1
PGND
GND
SENSE
–
FB
SENSE
+
SHDN
1
2
3
4
5
6
7
8
16 G2
15 PV
CC2
14 V
CC
13 I
FB
12 I
MAX
11 FREQSET
10 COMP
9
SS
ORDER PART
NUMBER
TOP VIEW
LTC3832EGN
GN
PART MARKING
3832
GN PACKAGE
16-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 130°C/ W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
q
denotes specifications that apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. V
CC
, PV
CC1
, PV
CC2
= 5V, unless otherwise noted. (Note 2)
SYMBOL
V
CC
PV
CC
V
UVLO
V
FB
V
OUT
∆V
OUT
PARAMETER
Supply Voltage
PV
CC1
, PV
CC2
Voltage
Undervoltage Lockout Voltage
Feedback Voltage
Output Voltage
Output Load Regulation
Output Line Regulation
V
COMP
= 1.25V
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
q
(Note 7)
V
COMP
= 1.25V
q
I
OUT
= 0A to 10A (Note 6)
V
CC
= 4.75V to 5.25V
2
U
U
W
W W
U
W
(Note 1)
Junction Temperature ........................................... 125°C
Operating Temperature Range (Note 9) .. – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
G1 1
PV
CC1
2
GND 3
FB 4
8
7
6
5
G2
V
CC
/PV
CC2
COMP
SS
LTC3832-1ES8
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 130°C/ W
S8
PART MARKING
38321
MIN
3
3
q
TYP
5
2.4
MAX
8
13.2
2.9
0.605
0.607
2.538
2.550
UNITS
V
V
V
V
V
V
V
mV
mV
0.595
0.593
2.462
2.450
0.6
0.6
2.5
2.5
2
0.1
sn3832 3832fs
LTC3832/LTC3832-1
The
q
denotes specifications that apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. V
CC
, PV
CC1
, PV
CC2
= 5V, unless otherwise noted. (Note 2)
SYMBOL
I
VCC
I
PVCC
f
OSC
V
SAWL
V
SAWH
V
COMPMAX
A
V
g
m
I
COMP
I
MAX
PARAMETER
Supply Current
PV
CC
Supply Current
Internal Oscillator Frequency
V
COMP
at Minimum Duty Cycle
V
COMP
at Maximum Duty Cycle
Maximum V
COMP
Error Amplifier Open-Loop DC Gain
Error Amplifier Transconductance
Error Amplifier Output Sink/Source Current
I
MAX
Sink Current
I
MAX
Sink Current Tempco
V
IH
V
IL
I
IN
I
SS
I
SSIL
R
SENSE
R
SENSEFB
t
r
, t
f
t
NOV
DC
MAX
SHDN Input High Voltage
SHDN Input Low Voltage
SHDN Input Current
Soft-Start Source Current
Maximum Soft-Start Sink Current
In Current Limit
SENSE Input Resistance
SENSE to FB Resistance
Driver Rise/Fall Time
Driver Nonoverlap Time
Maximum G1 Duty Cycle
Figure 2, PV
CC1
= PV
CC2
= 5V (Note 5)
Figure 2, PV
CC1
= PV
CC2
= 5V (Note 5)
Figure 2, V
FB
= 0V (Note 5), PV
CC1
= 8V
q
q
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
Figure 2, V
SHDN
= V
CC
V
SHDN
= 0V
Figure 2, V
SHDN
= V
CC
(Note 3)
V
SHDN
= 0V
FREQSET Floating
q
q
q
q
q
MIN
TYP
0.7
1
20
0.1
MAX
1.6
10
30
10
360
UNITS
mA
µA
mA
µA
kHz
V
V
V
kHz/µA
dB
230
300
1.2
2.2
V
FB
= 0V, PV
CC1
= 8V
Measured from FB to COMP,
SENSE
+
and SENSE
–
Floating, (Note 4)
Measured from FB to COMP,
SENSE
+
and SENSE
–
Floating, (Note 4)
V
IMAX
= V
CC
(Note 10)
V
IMAX
= V
CC
(Note 6)
q
q
q
q
2.85
10
50
1600
65
2000
100
q
∆f
OSC
/∆I
FREQSET
Frequency Adjustment
2400
µmho
µA
8
4
2.4
12
12
3300
16
20
µA
µA
ppm/°C
V
0.8
0.1
–8
–12
1.6
23.7
18
80
25
91
120
95
250
250
1
–18
V
µA
µA
mA
kΩ
kΩ
ns
ns
%
V
SHDN
= V
CC
V
SS
= 0V, V
IMAX
= 0V, V
IFB
= V
CC
V
IMAX
= V
CC
, V
IFB
= 0V,
V
SS
= V
CC
(Note 8), PV
CC1
= 8V
q
q
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to ground unless otherwise
specified.
Note 3:
Supply current in normal operation is dominated by the current
needed to charge and discharge the external FET gates. This will vary with
the LTC3832 operating frequency, operating voltage and the external FETs
used.
Note 4:
The open-loop DC gain and transconductance from the SENSE
+
and SENSE
–
pins to COMP pin will be (A
V
)(0.6/2.5) and (g
m
)(0.6/2.5)
respectively.
Note 5:
Rise and fall times are measured using 10% and 90% levels. Duty
cycle and nonoverlap times are measured using 50% levels.
Note 6:
Guaranteed by design, not subject to test.
Note 7:
PV
CC1
must be higher than V
CC
by at least 2.5V for G1 to operate
at 95% maximum duty cycle and for the current limit protection circuit to
be active.
Note 8:
The current limiting amplifier can sink but cannot source current.
Under normal (not current limited) operation, the output current will be
zero.
Note 9:
The LTC3832E/LTC3832-1E are guaranteed to meet performance
specifications from 0°C to 70°C. Specifications over the –40°C to 85°C
operating temperature range are assured by design, characterization and
correlation with statistical process controls.
Note 10:
The minimum and maximum limits for I
MAX
over temperature
includes the intentional temperature coefficient of 3300ppm/°C. This
induced temperature coefficient counteracts the typical temperature
coefficient of the external power MOSFET on-resistance. This results in a
relatively flat current limit over temperature for the application.
sn3832 3832fs
3
LTC3832/LTC3832-1
TYPICAL PERFOR A CE CHARACTERISTICS
Load Regulation
T
A
= 25°C
2.53 REFER TO FIGURE 12
2.52
2.51
V
OUT
(V)
V
FB
(V)
ERROR AMPLIFIER TRANSCONDUCTANCE (µmho)
2.54
2.50
2.49
2.48
2.47
2.46
–15
–10
5
0
OUTPUT CURRENT (A)
–5
10
15
3832 G01
Output Voltage Temperature Drift
ERROR AMPLIFIER SINK/SOURCE CURRENT (µA)
2.55
2.54
2.53
2.52
V
OUT
(V)
2.51
2.50
2.49
2.48
2.47
2.46
40
30
20
∆V
OUT
(mV)
10
0
–10
–20
–30
–40
180
160
140
120
100
80
60
40
–50 –25
0
75
50
25
TEMPERATURE (°C)
100
125
ERROR AMPLIFIER OPEN-LOOP GIAN (dB)
REFER TO FIGURE 12
OUTPUT = NO LOAD
2.45
–50 –25
50
25
0
75
TEMPERATURE (°C)
Oscillator Frequency
vs Temperature
360
350
FREQSET FLOATING
OSCILLATOR FREQUENCY (kHz)
OSCILLATOR FREQUENCY (kHz)
340
330
320
310
300
290
280
270
260
250
240
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
125
V
SAWH
– V
SAWL
(V)
4
U W
100
3832 G04
3832 G07
Line Regulation
0.605
0.604
0.603
0.602
0.601
0.600
T
A
= 25°C
5
4
3
2
1
0
–1
–2
–3
–4
3
4
6
7
5
SUPPLY VOLTAGE (V)
8
3832 G02
Error Amplifier Transconductance
vs Temperature
2400
2300
2200
2100
2000
1900
1800
1700
1600
– 50 – 25
0
75
50
25
TEMPERATURE (°C)
100
125
∆V
FB
(mV)
0.599
0.598
0.597
0.596
0.595
–5
3832 G03
Error Amplifier Sink/Source
Current vs Temperature
50
200
Error Amplifier Open-Loop Gain
vs Temperature
70
65
60
55
–50
125
50
–50 –25
75
0
25
50
TEMPERATURE (°C)
100
125
3830 G05
3832 G06
Oscillator Frequency
vs FREQSET Input Current
700
600
500
400
300
200
100
0
–30
T
A
= 25°C
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
10
0
20
–20
–10
FREQSET INPUT CURRENT (µA)
30
3832 G08
Oscillator (V
SAWH
– V
SAWL
)
vs External Sync Frequency
T
A
= 25°C
0.5
100
300
200
400
EXTERNAL SYNC FREQUENCY (kHz)
500
3832 G09
sn3832 3832fs
LTC3832/LTC3832-1
TYPICAL PERFOR A CE CHARACTERISTICS
Maximum G1 Duty Cycle
vs Temperature
100
99
MAXIMUM G1 DUTY CYCLE (%)
V
FB
= 0V
REFER TO FIGURE 3
I
MAX
SINK CURRENT (µA)
98
97
96
95
94
93
92
91
–50
–25
0
25
75
50
TEMPERATURE (°C)
100
125
OUTPUT VOLTAGE (V)
Output Current Limit Threshold
vs Temperature
20
SOFT-START SOURCE CURRENT (µA)
19
OUTPUT CURRENT LIMIT (A)
18
17
16
15
14
13
12
11
10
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
–10
–11
–12
–13
–14
–15
–16
– 50 – 25
0
75
50
25
TEMPERATURE (°C)
100
125
SOFT-START SINK CURRENT (mA)
REFER TO FIGURE 12 AND NOTE 10 OF
THE ELECTRICAL CHARACTERISTICS
UNDERVOLTAGE LOCKOUT THRESHOLD VOLTAGE (V)
Undervoltage Lockout Threshold
Voltage vs Temperature
3.0
V
CC
OPERATING SUPPLY CURRENT (mA)
2.9
2.8
2.7
2.6
2.5
2.4
2.3
2.2
2.1
2.0
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
PV
CC
SUPPLY CURRENT (mA)
U W
3832 G10
3832 G13
3832 G16
I
MAX
Sink Current
vs Temperature
20
18
16
14
12
10
8
0.5
3.0
2.5
2.0
1.5
1.0
Output Overcurrent Protection
T
A
= 25°C
REFER TO FIGURE 12
6
4
– 50 – 25
0
0
75
50
25
TEMPERATURE (°C)
100
125
0
2
4
6 8 10 12 14 16 18 20
OUTPUT CURRENT (A)
3832 G12
3832 G11
Soft-Start Source Current
vs Temperature
–8
–9
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
Soft-Start Sink Current
vs (V
IFB
– V
IMAX
)
T
A
= 25°C
0
–150
–125
–100
–50
–75
V
IFB
– V
IMAX
(mV)
–25
0
3832 G15
3830 G14
V
CC
Operating Supply Current
vs Temperature
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
125
FREQSET FLOATING
90
80
70
60
50
40
30
20
10
0
PV
CC
Supply Current
vs Oscillator Frequency
T
A
= 25°C
G1 AND G2 LOADED
WITH 6800pF,
PV
CC1,2
= 12V
G1 AND G2
LOADED
WITH 1000pF,
PV
CC1,2
= 5V
G1 AND G2
LOADED
WITH 6800pF,
PV
CC1,2
= 5V
0
400
100
300
200
OSCILLATOR FREQUENCY (kHz)
500
3832 G18
3832 G17
sn3832 3832fs
5
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