LTC3704
Wide Input Range, No R
SENSE
TM
Positive-to-Negative DC/DC Controller
FEATURES
s
s
s
DESCRIPTIO
s
s
s
s
s
s
s
s
s
s
High Efficiency Operation (No Sense
Resistor Required)
Wide Input Voltage Range: 2.5V to 36V
Current Mode Control Provides Excellent Transient
Response
High Maximum Duty Cycle (Typ 92%)
±1%
Internal Voltage Reference
±2%
RUN Pin Threshold with 100mV Hysteresis
Micropower Shutdown: I
Q
= 10µA
Programmable Switching Frequency
(50kHz to 1MHz) with One External Resistor
Synchronizable to an External Clock Up to 1.3
×
f
OSC
User-Controlled Pulse Skip or Burst Mode
®
Operation
Internal 5.2V Low Dropout Voltage Regulator
Capable of Operating with a Sense Resistor for High
Output Voltage Applications (V
DS
>36V)
Small 10-Lead MSOP Package
The LTC
®
3704 is a wide input range, current mode,
positive-to-negative DC/DC controller that drives an
N-channel power MOSFET and requires very few external
components. Intended for low to high power applications,
it eliminates the need for a current sense resistor by
utilizing the power MOSFET’s on-resistance, thereby maxi-
mizing efficiency.
The IC’s operating frequency can be set with an external
resistor over a 50kHz to 1MHz range, and can be synchro-
nized to an external clock using the MODE/SYNC pin.
Burst Mode operation at light loads, a low minimum
operating supply voltage of 2.5V and a low shutdown
quiescent current of 10µA make the LTC3704 ideally
suited for battery-operated systems.
For applications requiring constant frequency operation,
the Burst Mode operation feature can be defeated using
the MODE/SYNC pin. Higher than 36V switch voltage
applications are possible with the LTC3704 by connecting
the SENSE pin to a resistor in the source of the power
MOSFET.
The LTC3704 is available in the 10-lead MSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
No R
SENSE
is a trademark of Linear Technology Corporation.
APPLICATIO S
s
s
s
s
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SLIC Power Supplies
Telecom Power Supplies
Portable Electronic Equipment
Cable and DSL Modems
Router Supplies
TYPICAL APPLICATIO
R1
1M
1
2
RUN
I
TH
LTC3704
R
C
3k
3
4
5
C
C1
4.7nF
R
T
80.6k
1%
R
FB1
1.21k
1%
R
FB2
3.65k
1%
NFB
FREQ
MODE/SYNC
INTV
CC
GATE
GND
SENSE
V
IN
•
L1*
10
9
C
DC
47µF
V
IN
5V to 15V
V
OUT
–5.0V
3A to 5A
L2*
•
EFFICIENCY (%)
8
7
6
D1
C
VCC
4.7µF
C
IN
47µF
M1
C
OUT
100µF
(X2)
GND
3704 TA01
C
IN
, C
DC
: TDK C5750X5R1C476M
C
OUT
: TDK C5750X5R0J107M
C
VCC
: TAIYO YUDEN LMK316BJ475ML
D1: MBRD835L (ON SEMICONDUCTOR)
L1, L2: BH ELECTRONICS BH510-1009
M1: Si4884 (SILICONIX/VISHAY)
Figure 1. High Efficiency Positive to Negative Supply
sn3704 3704fs
U
Conversion Efficiency
100
90
80
70
60
V
IN
= 10V
50
40
30
20
0.001
0.01
1.0
0.1
OUTPUT CURRENT (A)
10
3704 TA01b
U
U
V
IN
= 5V
V
IN
= 15V
1
LTC3704
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
TOP VIEW
RUN
I
TH
NFB
FREQ
MODE/
SYNC
1
2
3
4
5
10
9
8
7
6
SENSE
V
IN
INTV
CC
GATE
GND
V
IN
Voltage ............................................... – 0.3V to 36V
INTV
CC
Voltage ........................................... – 0.3V to 7V
INTV
CC
Output Current ........................................ 50mA
GATE Voltage ........................... – 0.3V to V
INTVCC
+ 0.3V
I
TH
Voltage ............................................... – 0.3V to 2.7V
NFB Voltage .............................................. –2.7V to 2.7V
RUN, MODE/SYNC Voltages ....................... – 0.3V to 7V
FREQ Voltage ............................................– 0.3V to 1.5V
SENSE Pin Voltage ................................... – 0.3V to 36V
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Junction Temperature (Note 3) ............................ 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
LTC3704EMS
MS PACKAGE
10-LEAD PLASTIC MSOP
MS PART MARKING
LTYT
T
JMAX
= 125°C,
θ
JA
= 120°C/ W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
IN
= V
INTVCC
= 5V, V
RUN
= 1.5V, R
T
= 80k, V
MODE/SYNC
= 0V, unless otherwise specified.
SYMBOL
V
IN(MIN)
I
Q
PARAMETER
Minimum Input Voltage
Input Voltage Supply Current
Continuous Mode
Burst Mode Operation, No Load
Shutdown Mode
Rising RUN Input Threshold Voltage
Falling RUN Input Threshold Voltage
q
CONDITIONS
MIN
2.5
TYP
MAX
UNITS
V
Main Control Loop
(Note 4)
V
MODE/SYNC
= 5V, V
ITH
= 0.75V
V
MODE/SYNC
= 0V, V
ITH
= 0.2V (Note 5)
V
RUN
= 0V
1.223
1.198
50
V
ITH
= 0.2V (Note 5)
q
550
250
10
1.348
1.248
100
1
–1.218
–1.212
–1.230
7.5
0.002
q
1000
500
20
1.273
1.298
150
100
–1.242
–1.248
15
0.02
V
RUN+
V
RUN–
V
RUN(HYST)
I
RUN
V
NFB
I
NFB
∆V
NFB
∆V
IN
∆V
NFB
∆V
ITH
g
m
V
ITH(BURST)
I
SENSE(ON)
I
SENSE(OFF)
RUN Pin Input Threshold Hysteresis
RUN Input Current
Negative Feedback Voltage
NFB Pin Input Current
Line Regulation
Load Regulation
Error Amplifier Transconductance
Burst Mode Operation I
TH
Pin Voltage
SENSE Pin Current (GATE High)
SENSE Pin Current (GATE Low)
V
ITH
= 0.2V (Note 5)
2.5V
≤
V
IN
≤
30V
V
MODE/SYNC
= 0V, V
TH
= 0.5V to 0.90V (Note 5)
I
TH
Pin Load =
±5µA
(Note 5)
Falling I
TH
Voltage (Note 5)
Duty Cycle < 20%
V
SENSE
= 0V
V
SENSE
= 30V
120
–1
– 0.1
650
0.3
150
40
0.1
180
75
5
V
SENSE(MAX)
Maximum Current Sense Input Threshold
sn3704 3704fs
2
U
µA
µA
µA
V
V
V
mV
nA
V
V
µA
%/V
%
µmho
V
mV
µA
µA
W
U
U
W W
W
LTC3704
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
IN
= V
INTVCC
= 5V, V
RUN
= 1.5V, R
FREQ
= 80k, V
MODE/SYNC
= 0V, unless otherwise specified.
SYMBOL
Oscillator
f
OSC
D
MAX
f
SYNC/
f
OSC
t
SYNC(MIN)
t
SYNC(MAX)
V
IL(MODE)
V
IH(MODE)
R
MODE/SYNC
V
FREQ
V
INTVCC
∆V
INTVCC
∆V
IN1
∆V
INTVCC
∆V
IN2
V
LDO(LOAD)
V
DROPOUT
I
INTVCC
GATE Driver
t
r
t
f
GATE Driver Output Rise Time
GATE Driver Output Fall Time
C
L
= 3300pF (Note 7)
C
L
= 3300pF (Note 7)
17
8
100
100
ns
ns
Oscillator Frequency
Oscillator Frequency Range
Maximum Duty Cycle
Recommended Maximum Synchronized
Frequency Ratio
MODE/SYNC Minimum Input Pulse Width
MODE/SYNC Maximum Input Pulse Width
Low Level MODE/SYNC Input Voltage
High Level MODE/SYNC Input Voltage
MODE/SYNC Input Pull-Down Resistance
Nominal FREQ Pin Voltage
INTV
CC
Regulator Output Voltage
INTV
CC
Regulator Line Regulation
INTV
CC
Regulator Line Regulation
INTV
CC
Load Regulation
INTV
CC
Regulator Dropout Voltage
Bootstrap Mode INTV
CC
Supply
Current in Shutdown
V
IN
= 7.5V
7.5V
≤
V
IN
≤
15V
15V
≤
V
IN
≤
30V
0
≤
I
INTVCC
≤
20mA
V
IN
= 5V, INTV
CC
Load = 20mA
RUN = 0V, SENSE = 5V
–2
5.0
1.2
50
0.62
5.2
8
70
– 0.2
280
10
20
5.4
25
200
f
OSC
= 300kHz (Note 6)
V
SYNC
= 0V to 5V
V
SYNC
= 0V to 5V
R
FREQ
= 80k
250
50
87
92
1.25
25
0.8/f
OSC
0.3
300
350
1000
97
1.30
ns
ns
V
V
kΩ
V
V
mV
mV
%
mV
µA
kHz
kHz
%
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
ELECTRICAL CHARACTERISTICS
Low Dropout Regulator
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2:
The LTC3704E is 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 3:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
T
J
= T
A
+ (P
D
• 120°C/W)
Note 4:
The dynamic input supply current is higher due to power MOSFET
gate charging (Q
G
• f
OSC
). See Applications Information.
Note 5:
The LTC3704 is tested in a feedback loop that servos V
NFB
to the
reference voltage with the I
TH
pin forced to a voltage between 0V and 1.4V
(the no load to full load operating voltage range for the I
TH
pin is 0.3V to
1.23V).
Note 6:
In a synchronized application, the internal slope compensation
gain is increased by 25%. Synchronizing to a significantly higher ratio will
reduce the effective amount of slope compensation, which could result in
subharmonic oscillation for duty cycles greater than 50%.
Note 7:
Rise and fall times are measured at 10% and 90% levels.
sn3704 3704fs
3
LTC3704
TYPICAL PERFOR A CE CHARACTERISTICS
NFB Voltage vs Temp
–1.25
–1.231
NFB CURRENT (µA)
–1.24
NFB VOLTAGE (V)
NFB VOLTAGE (V)
–1.23
–1.22
–1.21
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3704
G01
Shutdown Mode I
Q
vs V
IN
30
20
SHUTDOWN MODE I
Q
(µA)
SHUTDOWN MODE I
Q
(µA)
20
Burst Mode I
Q
(µA)
10
0
0
10
20
V
IN
(V)
30
Burst Mode I
Q
vs Temperature
500
18
16
400
Burst Mode I
Q
(µA)
TIME (ns)
I
Q
(mA)
300
200
100
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3704 G07
4
U W
NFB Voltage Line Regulation
8.0
7.9
7.8
7.7
7.6
7.5
7.4
7.3
7.2
7.1
–1.229
0
5
10
15
20
V
IN
(V)
25
30
35
NFB Pin Current vs Temperature
–1.230
7.0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3704 G03
3704 G02
Shutdown Mode I
Q
vs Temperature
V
IN
= 5V
Burst Mode I
Q
vs V
IN
600
500
15
400
300
200
100
10
5
40
3704 G04
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3704 G05
0
0
10
20
V
IN
(V)
30
40
3704 G06
Dynamic I
Q
vs Frequency
C
L
= 3300pF
I
Q(TOT)
= 550µA + Qg • f
Gate Drive Rise and Fall Time
vs C
L
60
50
14
12
10
8
6
4
40
RISE TIME
30
20
FALL TIME
10
2
0
0
200
400
600
800
FREQUENCY (kHz)
1000
1200
0
0
2000
4000
6000 8000
C
L
(pF)
10000 12000
3704 G09
3704
G08
sn3704 3704fs
LTC3704
TYPICAL PERFOR A CE CHARACTERISTICS
RUN Thresholds vs V
IN
1.5
1.40
RUN THRESHOLDS (V)
1.4
RUN THRESHOLDS (V)
R
T
(kΩ)
0
25 50 75 100 125 150
TEMPERATURE (°C)
3704
G11
1.3
1.2
0
10
20
V
IN
(V)
30
Frequency vs Temperature
325
320
GATE FREQUENCY (kHz)
155
160
310
305
300
295
290
285
280
275
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3704
G13
150
SENSE PIN CURRENT (µA)
315
MAX SENSE THRESHOLD (mV)
INTV
CC
Load Regulation
T
A
= 25°C
5.2
DROPOUT VOLTAGE (mV)
INTV
CC
VOLTAGE (V)
INTV
CC
VOLTAGE (V)
5.1
5.0
0
10
20
30 40
50 60
INTV
CC
LOAD (mA)
70
80
U W
3704 G10
3704
G16
RUN Thresholds vs Temperature
1000
R
T
vs Frequency
1.35
1.30
100
1.25
40
1.20
–50 –25
10
0 100 200 300 400 500 600 700 800 900 1000
FREQUENCY (kHz)
3704
G12
Maximum Sense Threshold
vs Temperature
45
SENSE Pin Current vs Temperature
GATE HIGH
V
SENSE
= 0V
40
145
140
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3704 G14
35
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3704 G15
INTV
CC
Line Regulation
5.4
500
INTV
CC
Dropout Voltage
vs Current, Temperature
450
150°C
400
350
300
250
200
150
100
50
25°C
125°C
75°C
T
A
= 25°C
5.3
5.2
0°C
–50°C
5.1
0
5
10
15
20 25
V
IN
(V)
30
0
35
40
0
5
10
15
INTV
CC
LOAD (mA)
20
3704 G18
3704 G17
sn3704 3704fs
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