LTC3734
Single-Phase,
High Efficiency DC/DC
Controller for Intel Mobile CPUs
FEATURES
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DESCRIPTIO
Wide Input Voltage Range: 4V to 30V
±1%
Output Voltage Accuracy
6-Bit IMVP-IV VID Code: V
OUT
= 0.7V to 1.708V
Intel Compatible Power Saving Mode (PSIB)
Power Good Output with Adaptive Masking
Lossless Voltage Positioning
Resistor Programmable V
OUT
at Boot-Up and
Deeper Sleep State
Resistor Programmable Deep Sleep Offset
Programmable Fixed Frequency: 210kHz to 550kHz
Adjustable Soft-Start Current Ramping
Foldback Output Current Limit
Short-Circuit Shutdown Timer with Defeat Option
Overvoltage Protection
Available in 32-Lead 5mm
×
5mm
×
0.8mm (Profile)
QFN Package
The LTC
®
3734 is a single-phase synchronous step-down
switching regulator controller that drives all N-channel
power MOSFETs in a constant frequency architecture. The
output voltage is programmable by six VID bits during
normal operation and by external resistors during initial
boot-up and deeper sleep state. The LTC3734 drives its
output stage at frequencies up to 550kHz. Powerful on-
chip gate drivers eliminate the need for external gate driver
ICs, thus simplifying the design.
An Intel compatible PSIB input is provided to select between
two modes of operation. Fully enhanced synchronous mode
achieves a very small output ripple and very fast transient
response while power saving mode realizes very high ef-
ficiency. OPTI-LOOP
®
compensation allows the transient
response to be optimized for a wide range of output capaci-
tance and ESR values.
The LTC3734 is available in a small 5mm
×
5mm QFN
package. For 2-phase applications refer to the LTC3735.
, LTC and LT are registered trademarks of Linear Technology Corporation.
OPTI-LOOP is a registered trademark of Linear Technology Corporation.
APPLICATIO S
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Mobile and Desktop Computers
Internet Servers
TYPICAL APPLICATIO
MCH_PG
DPRSLPVR
STP_CPUB
PSIB
FREQSET
6-BIT VID
VID5-VID0
TG
SW
BG
PGND
SENSE
+
SENSE
–
M1
0.8μH
D1
0.002Ω
M2
100pF
R
C
3k
C
C
680pF
0.1μF
PGOOD
LTC3734
RBOOT
I
TH
RDPRSLP
RUN/SS
RDPSLP
SGND
V
OA+
OAOUT
V
OA–
12.7k
56.2k
1.27M
13.3k
13.3k
1.27M
4.5V TO 7V
4.7μF BAT54A
PV
CC
BOOST
0.47μF
SW
SV
CC
4.5V TO 7V
0.1μF
3734 F01
Figure 1. High Current Step-Down Converter
3734f
U
C
IN
10μF
35V
×4
V
IN
5V TO 24V
U
U
+
C
OUT
270μF
2V
×3
V
OUT
0.7V TO 1.708V
20A
1
LTC3734
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
DPRSLPVR
FREQSET
MCH_PG
PGOOD
BOOST
SV
CC
PSIB
V
FB
Input Supply Voltage (PV
CC
, SV
CC
) ............. 7V to – 0.3V
Topside Driver Voltages (BOOST) ..............38V to – 0.3V
Switch Voltage (SW) ....................................32V to – 5V
Boosted Driver Voltages (BOOST-SW) ........7V to – 0.3V
DPRSLPVR, STP_CPUB, MCH_PG, PGOOD,
RDPRSLP, RDPSLP, RBOOT Voltages ........5V to – 0.3V
RUN/SS, FREQSET, PSIB Voltages ..............7V to – 0.3V
VID0-VID5 Voltages .....................................5V to – 0.3V
V
FB
Voltage ................................................. 2V to – 0.3V
V
OA+
, V
OA–
Voltage ................................... 3.6V to –0.3V
Peak Gate Drive Current <1μs (TG, BG) ..................... 5A
Operating Ambient Temperature Range
(Note 2) .................................................. – 40°C to 85°C
Junction Temperature (Note 3) ............................. 125°C
Storage Temperature Range ................. – 65°C to 125°C
Reflow Peak Body Temperature ............................ 245°C
32 31 30 29 28 27 26 25
V
OA
+
1
24 TG
23 SW
22 PV
CC
21 BG
33
20 PGND
19 VID5
18 VID4
17 VID3
9 10 11 12 13 14 15 16
RBOOT
VID0
VID1
VID2
RDPSLP
RUN/SS
I
TH
NC
V
OA–
2
OAOUT 3
STP_CPUB 4
SGND 5
SENSE
+
6
SENSE
–
7
RDPRSLP 8
UH PACKAGE
32-LEAD PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 34°C/W
EXPOSED PAD (PIN 33) IS GROUND
MUST BE SOLDERED TO PCB
ORDER PART
NUMBER
LTC3734EUH
UH PART
MARKING
3734
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL
Reference
V
SENSEMAX
V
LOADREG
PARAMETER
Regulated Feedback Voltage
Maximum Current Sense Threshold
Output Voltage Load Regulation
Main Control Loop
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
PVCC
= V
SVCC
= 5V, V
RUN/SS
= 5V unless otherwise noted.
CONDITIONS
I
TH
Voltage = 0.5V; Measured at V
FB
(Note 4)
I
TH
Voltage = Max; V
CM
= 1.7V
(Note 4)
Measured in Servo Loop,
ΔI
TH
Voltage: 1.2V to 0.7V
Measured in Servo Loop,
ΔI
TH
Voltage: 1.2V to 2V
V
PVCC
= V
SVCC
= 4.5V to 7V
0.57
V
PSIB
= 0V
Measured with Respect to V
FB
= 0.6V
I
TH
= 1.2V, Sink/Source 25μA (Note 4)
I
TH
= 1.2V, (g
m
• Z
L
; No Ext Load) (Note 4)
VID = 010110, I
TH
= 0.5V (0°C – 85°C)
VID = 010110, I
TH
= 0.5V (Note 2)
●
●
●
●
●
MIN
TYP
0.600
MAX
UNITS
V
59
72
0.1
– 0.1
0.02
0.6
– 0.5
0.66
6
3
1.356
1.356
85
0.5
– 0.5
0.1
0.63
–1
0.68
7.5
1.370
1.376
V
REFLNREG
V
PSIB
I
PSIB
V
OVL
g
m
g
mOL
V
ACTIVE
Reference Voltage Line Regulation
Forced Continuous Threshold
Forced Continuous Current
Output Overvoltage Threshold
Transconductance Amplifier g
m
Transconductance Amplifier Gain
Output Voltage in Active Mode
0.64
4.5
1.342
1.336
mmho
V/mV
V
V
2
U
mV
%
%
%/V
V
μA
V
3734f
W
U
U
W W
W
LTC3734
ELECTRICAL CHARACTERISTICS
SYMBOL
I
Q
PARAMETER
Input DC Supply Current
Normal Mode
Shutdown
Undervoltage RUN/SS Reset
Soft-Start Charge Current
RUN/SS Pin ON Threshold
RUN/SS Pin Latchoff Threshold
RUN/SS Discharge Current
Shutdown Latch Disable Current
Total Sense Pins Source Current
Maximum Duty Factor
Top Gate Transition Time:
Rise Time
Fall Time
Bottom Gate Transition Time:
Rise Time
Fall Time
(Note 5)
V
RUN/SS
= 0V
V
CC
Lowered Until the RUN/SS Pin is Pulled Low
V
RUN/SS
= 1.9V
V
RUN/SS
Rising
V
RUN/SS
Rising from 3V
V
RUN/SS
Ramping Negative
Soft Short Condition V
FB
= 0.375V, V
RUN/SS
= 4.5V
V
FB
= 0.375V, V
RUN/SS
= 4.5V
V
SENSE
– = V
SENSE
+ = 0V
In Dropout
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
– 85
95
–5
3.2
–2.3
1.0
2
20
3.7
–1.5
1.5
3.9
3.2
–1.5
1.5
– 60
98.5
30
40
60
50
50
60
100
5.33
(Note 8)
●
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
PVCC
= V
SVCC
= 5V, V
RUN/SS
= 5V unless otherwise noted.
CONDITIONS
MIN
TYP
MAX
3
100
4.2
– 0.8
1.9
UNITS
mA
μA
V
μA
V
V
V
μA
5
μA
μA
%
90
90
90
90
ns
ns
ns
ns
ns
ns
ns
kΩ
0.25
0.3
0.7
±1
V
FREQSET
= 0V
V
FREQSET
= 1.2V
V
FREQSET
= 0V
V
FREQSET
≥
2.4V
I
PGOOD
= 2mA
V
PGOOD
= 5V
V
FB
with Respect to Set Output Voltage
V
FB
Ramping Negative
V
FB
Ramping Positive
–7
7
100
– 10
10
110
15
320
190
490
–2
355
210
550
0.1
–1
390
240
610
0.3
±1
– 13
13
120
%
V
V
μA
μA
kHz
kHz
kHz
V
μA
%
%
μs
cycles
UVR
I
RUN/SS
V
RUN/SS
V
RUN/SSLO
I
SCL
I
SDLHO
I
SENSE
DF
MAX
TG t
r
TG t
f
BG t
r
BG t
f
TG/BG t
1D
BG/TG t
2D
t
ON(MIN)
R
ATTEN
ATTEN
ERR
VID
THLOW
VID
THHIGH
VID
LEAK
Oscillator
I
FREQSET
f
NOM
f
LOW
f
HIGH
V
PGL
I
PGOOD
V
PG
V
RUN/SSARM
RUN/SS Pin Latchoff Arming
Top Gate Off to Bottom Gate On Delay C
LOAD
= 3300pF (Note 6)
Synchronous Switch-On Delay Time
Bottom Gate Off to Top Gate On Delay C
LOAD
= 3300pF (Note 6)
Top Switch-On Delay Time
Minimum On-Time
VID Top Resistance
Resistive Divider Error
VID0 to VID5 Logic Threshold Low
VID0 to VID5 Logic Threshold High
VID0 to VID5 Leakage
FREQSET Input Current
Nominal Frequency
Lowest Frequency
Highest Frequency
PGOOD Voltage Low
PGOOD Leakage Current
PGOOD Trip Level
– 0.25
Tested with a Square Wave (Note 7)
VID Parameters
PGOOD Output
t
MASK
t
DELAY
PGOOD Mask Timer
MCH_PG Delay Time
3734f
3
LTC3734
ELECTRICAL CHARACTERISTICS
SYMBOL
IB
VOS
CM
CMRR
ICL
AVOL
GBP
SR
VO(MAX)
PARAMETER
Input Bias Current
Input Offset Voltage Magnitude
Common Mode Input Voltage Range
Common Mode Rejection Ratio
Output Source Current
Open-Loop DC Gain
Gain-Bandwidth Product
Slew Rate
Maximum High Output Voltage
Operational Amp
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
PVCC
= V
SVCC
= 5V, V
RUN/SS
= 5V unless otherwise noted.
CONDITIONS
MIN
TYP
15
VOA+ = VOA– 1.2V, IOUT = 1mA
0
IOUT = 1mA
IOUT = 1mA
IOUT = 1mA
RL = 2k
IOUT = 1mA
46
10
70
35
30
2
5
PVCC – 1.2PVCC – 0.9
0.8
MAX
200
5
PVCC – 1.4
UNITS
nA
mV
V
dB
mA
V/mV
MHz
V/μs
V
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
The LTC3734E 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:
LTC3734EUH: T
J
= T
A
+ (P
D
• 34°C/W)
Note 4:
The LTC3734 is tested in a feedback loop that servos V
ITH
to a
specified voltage and measures the resultant V
FB
.
Note 5:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 6:
Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 7:
The minimum on-time condition corresponds to the on inductor
peak-to-peak ripple current
≥
40% I
MAX
(see Minimum On-Time
Considerations in the Applications Information section).
Note 8:
The ATTEN
ERR
specification is in addition to the output voltage
accuracy specified at VID code = 010110.
TYPICAL PERFOR A CE CHARACTERISTICS
Active Mode Efficiency
(VID = 1.186V, PSI = 0) (Figure 9)
100
90
90
EFFICIENCY (%)
V
IN
= 20V
80
V
IN
= 7.5V
EFFICIENCY (%)
80
EFFICIENCY (%)
70
60
60
0
2
4
I
OUT
(A)
6
4
U W
8
3735 GO1
Deeper Sleep Mode Efficiency
(Figure 9)
100
Efficiency vs Input Voltage
(Figure 9)
I
OUT
= 20A
V
OUT
= 1.6V
V
IN
= 7.5V
90
V
IN
= 20V
80
70
70
10
60
0.01
0.1
I
OUT
(A)
1
10
3734 G02
50
5
15
10
INPUT VOLTAGE (V)
20
3734 G03
3734f
LTC3734
TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs SV
CC
Voltage
and Mode
2500
ON
2000
SUPPLY CURRENT (μA)
1500
V
SENSE
(mV)
V
SENSE
(mV)
0
20
40
60
DUTY FACTOR (%)
80
100
3734 G05
1000
500
SHUTDOWN
0
4
5
6
SV
CC
VOLTAGE (V)
7
3734 G04
Maximum Current Sense Threshold
vs V
RUN/SS
(Soft-Start)
80
70
60
V
SENSE
(mV)
72
V
SENSE(CM)
= 1.25V
V
SENSE
(mV)
V
SENSE
(mV)
50
40
30
20
10
0
0
1
2
3
V
RUN/SS
(V)
4
5
3734 G07
Load Regulation (without AVP)
0.0
V
PSIB
= 5V
V
IN
= 15V
FIGURE 1
100
NORMALIZED V
OUT
(%)
–0.1
–0.2
I
SENSE
(μA)
–0.3
–0.4
0
5
U W
Maximum Current Sense Threshold
vs Duty Factor
75
80
70
60
Maximum Current Sense Threshold
vs Percent of Nominal Output
Voltage (Foldback)
50
50
40
30
20
10
25
0
0
50
0
100
25
75
PERCENT OF NOMINAL OUTPUT VOLTAGE (%)
3734 G06
Maximum Current Sense Threshold
vs Sense Common Mode Voltage
76
90
80
70
60
50
40
30
20
10
64
0
–10
–20
60
0
1
3
4
2
COMMON MODE VOLTAGE (V)
5
3734 G08
Current Sense Threshold
vs I
TH
Voltage
68
–30
0
0.5
1
1.5
V
ITH
(V)
2
2.5
3734 G09
SENSE Pins Total Source Current
50
0
–50
15
10
LOAD CURRENT (A)
20
25
3734 G10
–100
0
2
4
6
3734 G12
V
SENSE
COMMON MODE VOLTAGE (V)
3734f
5
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