LTC1753
5-Bit Programmable
Synchronous Switching
Regulator Controller for
Pentium
®
III Processor
FEATURES
s
s
s
s
s
s
s
s
s
DESCRIPTIO
s
s
s
5-Bit Digitally Programmable 1.3V to 3.5V Fixed
Output Voltage, VRM 8.4 Compliant
Fast Transient Response: 0% to 100% Duty Cycle
Phase Lead Compensation for Remote Sensing
Overtemperature Protection
Flags for Power Good and Overvoltage Fault
19A Output Current Capability from a 5V Supply
Dual N-Channel MOSFET Synchronous Driver
Initial Output Accuracy:
±1.5%
Excellent Output Accuracy:
±2%
Typ Over Line,
Load and Temperature Variations
High Efficiency: Over 95% Possible
Adjustable Current Limit Without External Sense
Resistors
Available in 2O-Lead SSOP and SW Packages
APPLICATIO S
s
s
Power Supply for Pentium
®
III, AMD-K6
®
-2, SPARC,
ALPHA and PA-RISC Microprocessors
High Power 5V to 1.3V-3.5V Regulators
The LTC
®
1753 is a high power, high efficiency switching
regulator controller optimized for 5V input to a digitally
programmable 1.3V-3.5V output. The internal 5-bit DAC
programs the output voltage from 1.3V to 2.05V in 50mV
increments and from 2.1V to 3.5V in 100mV increments. The
precision internal reference and an internal feedback system
provide an output accuracy of
±1.5%
at room temperature
and typically
±2%
over temperature, load current and line
voltage shifts. The LTC1753 uses a synchronous switching
architecture with two external N-channel output devices,
providing high efficiency and eliminating the need for a high
power, high cost P-channel device. Additionally, it senses the
output current across the on-resistance of the upper N-
channel FET, providing an adjustable current limit without an
external low value sense resistor.
The LTC1753 free-runs at 300kHz and can be synchronized
to a faster external clock if desired. It provides a phase lead
compensation scheme and under harsh loading conditions,
the PWM duty cycle can be momentarily forced to 0% or
100% to reduce the output voltage recovery time.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Pentium is a registered trademark of Intel Corporation.
AMD-K6 is a registered trademark of Advanced Micro Devices, Inc.
TYPICAL APPLICATIO
5.6k
PV
CC
12V
V
IN
5V
+
0.1µF
5.6k
10µF
600Ω
0.1µF
+
10µF
Q1A*
PWRGD
FAULT
CPU
5
VID0 TO VID4
OUTEN
COMP
R
C
15k
C
C
4700pF
SS
SGND
GND
SENSE
LTC1753
Q2A*
G2
V
FB
NC
Q2*
V
CC
I
MAX
PV
CC
G1
20Ω
I
FB
C
OUT
††
2700µF
×
5
Q1*
L
O
†
1.3µH
18A
V
OUT
1.3V TO
3.5V
14A
C1
150pF
C
SS
0.1µF
1µF
* SILICONIX SUD50N03-10
** SANYO 10MV1200GX
†
PANASONIC ETQP 6FIR3LFA
††
SANYO 6MV2700GX
Figure 1. 5V to 1.3V-3.5V Supply Application
U
+
C
IN
**
1200µF
×
4
U
U
+
1753 F01
1
LTC1753
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
G2
PV
CC
GND
SGND
V
CC
SENSE
I
MAX
I
FB
SS
1
2
3
4
5
6
7
8
9
20 G1
19 OUTEN
18 VID0
17 VID1
16 VID2
15 VID3
14 VID4
13 PWRGD
12 FAULT
11 V
FB
Supply Voltage
V
CC
........................................................................ 7V
PV
CC
................................................................... 14V
Input Voltage
I
FB
(Note 2) ............................................ PV
CC
+ 0.3V
I
MAX
........................................................ – 0.3V to 9V
All Other Inputs ...................... – 0.3V to (V
CC
+ 0.3V)
Digital Output Voltage ................................. – 0.3V to 9V
I
FB
Input Current (Notes 2, 3) .......................... – 100mA
Junction Temperature .......................................... 125°C
Operating Temperature Range ..................... 0°C to 70°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec.)................. 300°C
ORDER PART
NUMBER
LTC1753CG
LTC1753CSW
COMP 10
G PACKAGE
SW PACKAGE
20-LEAD PLASTIC SSOP 20-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 100°C/ W (G)
T
JMAX
= 125°C,
θ
JA
= 100°C/ W (SW)
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
CC
= 5V, PV
CC
= 12V, unless otherwise noted. (Note 3)
SYMBOL
V
CC
PV
CC
V
FB
PARAMETER
Supply Voltage
Supply Voltage for G1, G2
Internal Feedback Voltage
1.3V Output Voltage
2.1V Initial Output Voltage
3.5V Initial Output Voltage
With Respect to Rated Output Voltage (Figure 2)
– 20 (– 1.5%)
– 27 (– 1.5%)
– 42 (– 1.5%)
– 52 (– 1.5%)
– 26 (– 2%)
– 36 (– 2%)
– 56 (– 2%)
– 70 (– 2%)
–5
±1
q
q
q
q
q
CONDITIONS
q
q
MIN
4.5
TYP
MAX
6
13.2
UNITS
V
V
V
V
V
0.5
0.8
1.34
20 (+ 1.5%)
27 (+ 1.5%)
42 (+ 1.5%)
52 (+ 1.5%)
26 (+ 2%)
36 (+ 2%)
56 (+ 2%)
70 (+ 2%)
V
OUT
1.3V Initial Output Voltage
1.8V Initial Output Voltage
2.8V Initial Output Voltage
3.5V Initial Output Voltage
1.3V Initial Output Voltage
1.8V Initial Output Voltage
2.8V Initial Output Voltage
3.5V Initial Output Voltage
Output Load Regulation
Output Line Regulation
Positive Power Good Trip Point
Negative Power Good Trip Point
FAULT Trip Point
Operating Supply Current
Shutdown Supply Current
Supply Current
Internal Oscillator Frequency
V
COMP
at Minimum Duty Cycle
V
COMP
at Maximum Duty Cycle
q
q
q
q
∆V
OUT
V
PWRGD
V
FAULT
I
CC
I
PVCC
f
OSC
V
SAWL
V
SAWH
I
OUT
= 0 to 14A (Figure 2)
V
IN
= 4.75V to 5.25V, I
OUT
= 0 (Figure 2)
% Above Output Voltage (Note 4) (Figure 2)
% Below Output Voltage (Note 4) (Figure 2)
% Above Output Voltage (Note 4) (Figure 2)
OUTEN = V
CC
= 5V (Note 5)(Figure 3)
OUTEN = 0, VID0 to VID4 Floating (Figure 3)
PV
CC
= 12V, OUTEN = V
CC
(Note 6) (Figure 3)
PV
CC
= 12V, OUTEN = 0, VID0 to VID4 Floating
(Figure 4)
(Note 11)
(Note 11)
q
–6
8
3
–3
13
800
130
15
1
6
18
1200
250
250
300
1.8
2.8
350
2
U
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
%
%
%
µA
µA
mA
µA
kHz
V
V
W
U
U
W W
W
LTC1753
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
CC
= 5V, PV
CC
= 12V, unless otherwise noted. (Note 3)
SYMBOL
G
ERR
g
mERR
BW
ERR
I
IMAX
I
SS
I
SSIL
I
SSHIL
t
SSHIL
t
PWRGD
t
PWRBAD
t
FAULT
V
OTDD
V
SHDN
t
r
, t
f
t
NOL
V
IH
V
IL
R
SENSE
R
VID
I
SINK
PARAMETER
Error Amplifier Open-Loop DC Gain
Error Amplifier Transconductance
Error Amplifier – 3dB Bandwidth
I
MAX
Sink Current
Soft-Start Source Current
Maximum Soft-Start Sink Current
Under Current Limit
Soft-Start Sink Current Under Hard
Current Limit
Hard Current Limit Hold Time
Power Good Response Time↑
Power Good Response Time↓
FAULT Response Time
Overtemperature Driver Disable
Shutdown
Driver Rise and Fall Time
Driver Nonoverlap Time
VID0 to VID4 Input High Voltage
VID0 to VID4 Input Low Voltage
SENSE Input Resistance
VID0 to VID4 Internal Pull-Up
Resistance
Digital Output Sink Current
q
q
CONDITIONS
(Note 7)
(Note 7)
COMP = Open (Note 11)
V
IMAX
= V
CC
V
SS
= 0V, V
IMAX
= 0V, V
IFB
= V
CC
V
SENSE
= V
OUT
, V
IMAX
= V
CC
, V
IFB
= 0V
(Notes 8, 9), V
SS
= V
CC
V
SENSE
= 0V, V
IMAX
= V
CC
, V
IFB
= 0V
V
SENSE
= 0V, V
IMAX
= 4V, V
IFB
↓
from 5V
V
SENSE
↑
from 0V to Rated V
OUT
V
SENSE
↓
from Rated V
OUT
to 0V
V
SENSE
↑
from Rated V
OUT
to V
CC
OUTEN↓, VID0 to VID4 = 0 (Note 10) (Figure 3)
OUTEN↓, VID0 to VID4 = 0 (Note 10) (Figure 3)
(Figure 4)
(Figure 4)
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
MIN
40
0.9
150
– 16
30
20
TYP
54
1.6
400
190
– 12
60
45
500
MAX
2.3
230
–8
150
UNITS
dB
millimho
kHz
µA
µA
µA
mA
µs
0.5
200
200
1.6
1
500
500
1.7
90
2
1000
1000
1.8
0.8
150
ms
µs
µs
V
V
ns
ns
V
30
2
100
0.8
108
V
kΩ
kΩ
mA
10
10
20
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
When I
FB
is taken below GND, it will be clamped by an internal diode.
This pin can handle input currents greater than 100mA below GND without
latchup. In the positive direction, it is not clamped to V
CC
or PV
CC
.
Note 3:
All currents into device pins are positive; all currents out of the
device pins are negative. All voltages are referenced to ground unless
otherwise specified.
Note 4:
The Power Good and FAULT trip thresholds are tested at the 1.8V
output voltage code. The Power Good and FAULT trip thresholds are
guaranteed by design for all other output voltage codes to the same
specification.
Note 5:
The LTC1753 goes into the shutdown mode if VID0 to VID4 are
floating. Due to the internal pull-up resistors, there will be an additional
0.25mA/pin if any of the VID0 to VID4 pins are pulled low.
Note 6:
Supply current in normal operation is dominated by the current
needed to charge and discharge the external FET gates. This will vary with
the LTC1753 operating frequency, supply voltage and the external FETs
used.
Note 7:
The open-loop DC gain and transconductance from the SENSE pin to
COMP pin will be (G
ERR
)(1.26/3.3) and (g
mERR
)(1.26/3.3) respectively.
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:
Under typical soft current limit, the net soft-start discharge current
will be 60µA (I
SSIL
) + [– 12µA(I
SS
)]
≅
48µA. The soft-start sink-to-source
current ratio is designed to be 5:1.
Note 10:
When VID0 to VID4 are all HIGH, the LTC1753 will be forced to
shut down internally. The OUTEN trip voltages are guaranteed by design for
all other input codes.
Note 11:
This parameter is guaranteed by design and correlation and is not
tested in production.
3
LTC1753
TYPICAL PERFOR A CE CHARACTERISTICS
Typical 1.3V V
OUT
Distribution
50
TOTAL SAMPLE SIZE = 500
40
40
NUMBER OF UNITS
NUMBER OF UNITS
EFFICIENCY (%)
30
25°C
20
100°C
10
0
1.275
1.285
1.305 1.315
1.295
OUTPUT VOLTAGE (V)
Load Regulation
2.825
REFER TO TYPICAL APPLICATION
2.820 CIRCUIT FIGURE 1
V = 5V, PV
CC
= 12V, T
A
= 25°C
2.815
IN
OUTPUT VOLTAGE (V)
2.810
2.805
2.800
2.795
2.790
2.785
2.780
2.775
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
OUTPUT CURRENT (A)
1753 G04
OUTPUT VOLTAGE (V)
2.810
2.805
2.800
2.795
2.790
2.785
2.780
2.775
4.75
4.85
5.05
5.15
4.95
INPUT VOLTAGE (V)
5.25
1753 G05
OUTPUT VOLTAGE (V)
1.78
1.76
1.74
1.72
1.70
1.68
1.66
1.64
1.62
1.60
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
2.1
1.9
1.7
1.5
1.3
1.1
0.9
– 50 –25
ERROR AMPLIFIER OPEN-LOOP DC GAIN (dB)
1.80
OVER-TEMPERATURE DRIVER DISABLE (V)
ERROR AMPLIFIER TRANSCONDUCTANCE (millimho)
Overtemperature Driver Disable
vs Temperature
4
U W
1753 G07
Typical 2.8V V
OUT
Distribution
50
TOTAL SAMPLE SIZE = 500
100
90
80
25°C
30
100°C
20
70
60
50
40
30
10
20
10
1.325
1753 G01
Efficiency vs Load Current
A
B
REFER TO TYPICAL APPLICATION
CIRCUIT FIGURE 1
V
IN
= 5V, PV
CC
= 12V, V
OUT
= 2.8V,
C
OUT
= 330µF
×
7, L
O
= 2µH
A: Q1 = 1
×
SUD50N03-10
Q2 = 1
×
SUD50N03-10
B: Q1 = 2
×
SUD50N03-10
Q2 = 1
×
SUD50N03-10
NO FAN
Q1 IS MOUNTED ON 1IN
2
COPPER AREA
0
0.3
2
4
6
8
10
LOAD CURRENT (A)
12
14
0
2.75
0
2.77
2.81
2.83
2.79
OUTPUT VOLTAGE (V)
2.85
1753 G02
1753 G03
Line Regulation
2.825
2.820
2.815
REFER TO TYPICAL APPLICATION
CIRCUIT FIGURE 1
OUTPUT = NO LOAD
T
A
= 25°C
2.860
2.850
2.840
2.830
2.820
2.810
2.800
2.790
2.780
2.770
2.760
2.750
Output Temperature Drift
2.740
– 50 – 25
50
0
75
25
TEMPERATURE (°C)
100
125
1753 G06
Error Amplifier Transconductance
vs Temperature
2.3
60
Error Amplifier Open-Loop
DC Gain vs Temperature
55
50
45
50
25
75
0
TEMPERATURE (°C)
100
125
40
–50
–25
75
0
25
50
TEMPERATURE (°C)
100
125
1753 G08
1753 G09
LTC1753
TYPICAL PERFOR A CE CHARACTERISTICS
Oscillator Frequency
vs Temperature
350
340
OSCILLATOR FREQUENCY (kHz)
I
MAX
SINK CURRENT (µA)
220
210
200
190
180
170
160
150
–50
SOFT START SOURCE CURRENT (µA)
330
320
310
300
290
280
270
260
250
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
V
CC
Operating Supply Current
vs Temperature
1.2
V
CC
OPERATING SUPPLY CURRENT (mA)
V
CC
SHUTDOWN SUPPLY CURRENT (µA)
1.1
1.0
0.9
0.8
0.7
0.6
V
CC
= 5V
f
OSC
= 300kHz
200
175
150
125
100
75
50
– 50 – 25
0
75
50
25
TEMPERATURE (°C)
100
125
PV
CC
SUPPLY CURRENT (mA)
0.5
– 50 –25
50
25
75
0
TEMPERATURE (°C)
Output Over Current Protection
3.0
2.5
Q1 CASE = 90°C, V
OUT
= 2.8V
Q1 = 2
×
MTD20N03HDL
Q2 = 1
×
MTD20N03HDL
R
IMAX
= 2.7k, R
IFB
= 20Ω,
SS CAP = 0.01µF
OUTPUT VOLTAGE (V)
2.0
1.5
1.0
SHORT-CIRCUIT
CURRENT
0.5
0
0
2
4
6
8 10 12 14
OUTPUT CURRENT (A)
16
18
U W
1753 G10
I
MAX
Sink Current
vs Temperature
–8
–9
–10
–11
–12
–13
–14
–15
Soft-Start Source Current
vs Temperature
–25
75
0
50
25
TEMPERATURE (°C)
100
125
–16
– 50 – 25
50
25
75
0
TEMPERATURE (°C)
100
125
1753 G11
1753 G12
V
CC
Shutdown Supply Current
vs Temperature
250
225
70
60
50
40
30
20
10
0
PV
CC
Supply Current
vs Gate Capacitance
PV
CC
= 12V
T
A
= 25°C
100
125
0
2000
6000
GATE CAPACITANCE (pF)
4000
8000
1753 G15
1753 G13
1753 G14
Transient Response, V
OUT
= 2.8V
V
OUT
50mV/DIV
10
I
LOAD
5A/DIV
0
50µs/DIV
1753 G17
1753 G16
5
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