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LT1585

Datasheet LT1585, LT1584, LT1587 Datasheet (Linear Technology)

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LT1584/LT1585/LT1587
FEATURES
■
Fast Transient Response
■
Guaranteed Dropout Voltage at Multiple Currents
■
Load Regulation: 0.05% Typ
■
Trimmed Current Limit
■
On-Chip Thermal Limiting
■
Standard 3-Pin Power Package
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APPLICATIONS
■
PentiumTM Processor Supplies
■
PowerPCTM Supplies
■
Other 2.5V to 3.6V Microprocessor Supplies
■
Low Voltage Logic Supplies
■
Battery-Powered Circuitry
■
Post Regulator for Switching Supply
LT1585/7CM, LT1584/5/7CT Adjustable LT1585/7CM-3.3, LT1584/5/7CT-3.3 3.3V Fixed LT1585CM-3.38, LT1584/5CT-3.38 3.38V Fixed LT1585/7CM-3.45, LT1584/5/7CT-3.45 3.45V Fixed LT1585/7CM-3.6, LT1584/5/7CT-3.6 3.6V Fixed
7A, 4.6A, 3A Low Dropout
Fast Response
Positive Regulators
Adjustable and Fixed
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DESCRIPTION
The LT®1584/LT1585/LT1587 are low dropout three­terminal regulators with 7A, 4.6A and 3A output current capability, respectively. Design has been optimized for low voltage applications where transient response and mini­mum input voltage are critical. Similar to the LT1083/4/5 family, it has lower dropout voltage and faster transient response. These improvements make it ideal for low volt­age microprocessor applications requiring a regulated
2.5V to 3.6V output with an input supply below 7V. Current limit is trimmed to ensure specified output current
and controlled short-circuit current. On-chip thermal lim­iting provides protection against any combination of over­load that would create excessive junction temperatures.
The LT1585/LT1587 are available in both the through-hole and surface mount versions of the industry standard 3-pin TO-220 power package. The LT1584 is available in the through-hole 3-pin TO-220 power package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Pentium is a trademark of Intel Corporation. PowerPC is a trademark of IBM Corporation.
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TYPICAL APPLICATION
3.3V, 7A, 4.6A, 3A Regulator
LT1584-3.3
≥ 4.75V
V
IN
* REQUIRED FOR STABILITY LT1584: C2 = 22µF, LT1585/LT1587: C2 = 10µF
NOTE: MICROPROCESSOR APPLICATIONS WITH LOAD TRANSIENTS OF 3.8A REQUIRE OUTPUT DECOUPLING CAPACITANCE > 1300µF ON FIXED VOLTAGE PARTS TO ACHIEVE < 50mV OF DEVIATION FROM NOMINAL OUTPUT. CONSULT FACTORY FOR DETAILS
+
C1 10µF
LT1585-3.3 LT1587-3.3
+
3.3V 7A, 4.6A, 3A
C2* SOLID TANTALUM
1585 TA01
Dropout Voltage vs Output Current
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
INPUT/OUTPUT DIFFERENTIAL (V)
0.6
0.5 0
OUTPUT CURRENT (A)
I
FULL LOAD
1585 TA02
1
LT1584/LT1585/LT1587
WW
W
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ABSOLUTE MAXIMUM RATINGS
VIN............................................................................. 7V
Operating Junction Temperature Range
Control Section.................................... 0°C to 125°C
Power Transistor ................................. 0°C to 150°C
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W
PACKAGE/ORDER INFORMATION
FRONT VIEW
3
2
1
M PACKAGE
3-LEAD PLASTIC DD PAK
θJA = 30°C/W* θJA = 50°C/W
FRONT VIEW
3
2
1
VIN  V
OUT
 ADJ
VIN  V
OUT
 GND
ORDER PART
NUMBER
LT1585CM LT1587CM
LT1585CM-3.3 LT1585CM-3.38
LT1585CM-3.45 LT1585CM-3.6 LT1587CM-3.3
M PACKAGE
3-LEAD PLASTIC DD PAK
θJA = 30°C/W* θJA = 50°C/W
LT1587CM-3.45 LT1587CM-3.6
FRONT VIEW
T PACKAGE
3-LEAD PLASTIC TO-220
FRONT VIEW
T PACKAGE
3-LEAD PLASTIC TO-220
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
UUU
PRECONDITIONI G
100% Thermal Limit Functional Test
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ORDER PART
3
2
1
3
2
1
VIN
V
OUT
ADJ
VIN
V
OUT
GND
LT1584CT-3.3 LT1585CT-3.3
LT1587CT-3.3 LT1584CT-3.38 LT1585CT-3.38
NUMBER
LT1584CT LT1585CT LT1587CT
LT1584CT-3.45 LT1585CT-3.45 LT1587CT-3.45 LT1584CT-3.6 LT1585CT-3.6 LT1587CT-3.6
* With package soldered to 0.5 square inch copper area over backside
ground plane or internal power plane. θ >40°C/W with other mounting techniques.
can vary from 20°C/W to
JA
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
Reference Voltage LT1584 1.5V ≤ (VIN – V
LT1585 1.5V ≤ (VIN – V LT1587 1.5V ≤ (V
Output Voltage LT1584-3.3 4.75V ≤ VIN ≤ 6.3V, 0mA ≤ I
LT1585-3.3 4.75V ≤ VIN ≤ 7V, 0mA ≤ I LT1587-3.3 4.75V ≤ VIN ≤ 7V, 0mA ≤ I
LT1584-3.38 4.75V ≤ VIN ≤ 6.38V, 0mA ≤ I LT1585-3.38 4.75V ≤ VIN ≤ 7V, 0mA ≤ I
LT1584-3.45 4.75V ≤ VIN ≤ 6.45V, 0mA ≤ I LT1585-3.45 4.75V ≤ VIN ≤ 7V, 0mA ≤ I LT1587-3.45 4.75V ≤ VIN ≤ 7V, 0mA ≤ I
LT1584-3.6 4.75V ≤ VIN ≤ 7V, 0mA ≤ I LT1584-3.6 4.80V ≤ VIN ≤ 7V, 0mA ≤ I LT1584-3.6 4.80V ≤ VIN ≤ 6.6V, 0mA ≤ I LT1584-3.6 4.85V ≤ V
1.5V ≤ (VIN – V
IN
4.75V ≤ V
) ≤ 3V, 10mA ≤ I
OUT
) ≤ 5.75V, 10mA ≤ I
OUT
) ≤ 5.75V, 10mA ≤ I
OUT
– V
) ≤ 5.75V, 10mA ≤ I
OUT
≤ 7V, 0mA ≤ I
IN
≤ 6.6V, 0mA ≤ I
IN
≤ 7A
OUT
≤ 4.6A, TJ ≥ 25°C
OUT
≤ 4A, TJ < 25°C
OUT
≤ 3A ● 1.225 (– 2%) 1.250 1.275 (+2%) V
OUT
≤ 7A
OUT
≤ 4.6A, TJ ≥ 25°C
OUT
≤ 4A, TJ < 25°C
OUT
≤ 3A ● 3.235 (– 2%) 3.300 3.365 (+2%) V
OUT
≤ 7A
OUT
≤ 4A ● 3.313 (– 2%) 3.380 3.465 (+2.5%) V
OUT
≤ 7A
OUT
≤ 4A
OUT
≤ 3A ● 3.381 (– 2%) 3.450 3.519 (+2%) V
OUT
≤ 6A ● 3.400 (– 5.5%) 3.600 3.672 (+2%) V
OUT
≤ 6A ● 3.450 (– 4%) 3.600 3.672 (+2%) V
OUT
≤ 7A ● 3.431 (– 4.7%) 3.600 3.672 (+ 2%) V
OUT
≤ 7A ● 3.481 (– 3.3%) 3.600 3.672 (+ 2%) V
OUT
2
LT1584/LT1585/LT1587
ELECTRICAL CHARACTERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
Output Voltage LT1585/7-3.6 4.75V ≤ VIN ≤ 7V, 0mA ≤ I
LT1585/7-3.6 4.80V ≤ VIN ≤ 7V, 0mA ≤ I LT1585-3.6 4.80V ≤ VIN ≤ 7V, 0mA ≤ I LT1585-3.6 4.85V ≤ V
Line Regulation LT1584/5/7 2.75V ≤ VIN ≤ 7V, I (Notes 1, 2) LT1584/5/7-3.3 4.75V ≤ VIN ≤ 7V, I
LT1584/5-3.38 4.75V ≤ VIN ≤ 7V, I LT1584/5/7-3.45 4.75V ≤ V LT1584/5/7-3.6 4.75V ≤ VIN ≤ 7V, I
Load Regulation LT1584/5/7 (VN – V
≤ 7V, 0mA ≤ I
IN
OUT OUT OUT
≤ 7V, I
IN
OUT
OUT OUT
) = 3V, TJ = 25°C, 10mA ≤ I
(Notes 1, 2, 3) LT1584/5/7-3.3 VIN = 5V, TJ = 25°C, 0mA ≤ I
LT1584/5-3.38 VIN = 5V, TJ = 25°C, 0mA ≤ I LT1584/5/7-3.45 VIN = 5V, TJ = 25°C, 0mA ≤ I LT1584/5/7-3.6 VIN = 5.25V, TJ = 25°C, 0mA ≤ I
Dropout Voltage LT1585/7 ∆V
LT1585/7-3.3 ∆V LT1585-3.38 ∆V LT1585/7-3.45 ∆V LT1585/7-3.6 ∆V
LT1585 ∆V LT1585-3.3 ∆V LT1585-3.38 ∆V
LT1585-3.45 ∆V LT1585-3.6 ∆V
LT1584 ∆V LT1584-3.3 ∆V LT1584-3.38 ∆V LT1584-3.45 ∆V LT1584-3.6 ∆V
= 1%, I
REF
= 1%, I
OUT
= 1%, I
OUT
= 1%, I
OUT
= 1%, I
OUT
= 1%, I
REF
∆V
= 1%, I
REF
= 1%, I
OUT
∆V
= 1%, I
OUT
= 1%, I
OUT
= 1%, I
OUT
= 1%, I
OUT
= 1%, I
REF
= 1%, I
OUT
= 1%, I
OUT
= 1%, I
OUT
= 1%, I
OUT
T
≥ 25°C ● 1.200 1.300 V
J
= 3A
OUT
= 3A
OUT
= 3A
OUT
= 3A
OUT
= 3A ● 1.150 1.300 V
OUT
= 4.6A, TJ ≥ 25°C
OUT
= 4A, TJ < 25°C
OUT
= 4.6A, TJ ≥ 25°C
OUT
= 4A, TJ < 25°C
OUT
= 4A
OUT
= 4A
OUT
= 4A ● 1.200 1.400 V
OUT
= 6A
OUT
= 6A
OUT
= 6A
OUT
= 6A
OUT
= 6A
OUT
TJ < 25°C ● 1.200 1.350 V
LT1584 ∆V LT1584-3.3 ∆V LT1584-3.38 ∆V LT1584-3.45 ∆V LT1584-3.6 ∆V
Current Limit LT1584 (VIN – V (Note 3) LT1584-3.3 (VIN – V
LT1584-3.38 (VIN – V LT1584-3.45 (V LT1584-3.6 (VIN – V
LT1585 (VIN – V LT1585-3.3 (V
IN
IN
REF OUT OUT OUT OUT
– V
– V
= 1%, I
= 1%, I = 1%, I = 1%, I = 1%, I
OUT OUT OUT OUT OUT
OUT) OUT)
= 7A
OUT
= 7A
OUT
= 7A
OUT
= 7A
OUT
= 7A ● 1.250 1.400 V
OUT
) = 3V ) = 3V ) = 3V ) = 3V ) = 3V ● 7.100 8.250 A
= 5.5V
= 5.5V TJ ≥ 25°C ● 4.600 5.25 A TJ < 25°C ● 4.100 5.25 A
LT1585-3.38 (VIN – V LT1585-3.45 (V
IN
LT1585-3.6 (VIN – V LT1587 (V
LT1587-3.3 (V LT1587-3.45 (V LT1587-3.6 (V
IN IN IN IN
= 5.5V
OUT)
– V
= 5.5V
OUT)
= 5.5V ● 4.100 4.750 A
OUT)
– V
) = 5.5V
OUT
– V
) = 5.5V
OUT
– V
) = 5.5V
OUT
– V
) = 5.5V ● 3.100 3.750 A
OUT
≤ 3A ● 3.474 (– 3.5%) 3.600 3.672 (+ 2%) V
OUT
≤ 3A ● 3.528 (– 2%) 3.600 3.672 (+2%) V
OUT
≤ 4A ● 3.450 (– 4%) 3.600 3.672 (+ 2%) V
OUT
≤ 4A ● 3.492 (– 3%) 3.600 3.672 (+2%) V
OUT
= 10mA = 0mA = 0mA = 0mA = 0mA ● 0.005 0.2 %
≤ I
OUT
FULL LOAD
FULL LOAD
0.05 0.3 %
● 0.05 0.5 %
OUT OUT OUT
≤ I ≤ I ≤ I
OUT
FULL LOAD FULL LOAD FULL LOAD
≤ I
3
LT1584/LT1585/LT1587
ELECTRICAL CHARACTERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
Adjust Pin Current LT1584/5/7 ● 55 120 µA Adjust Pin Current LT1584 1.5V ≤ (V
Change (Note 3) LT1585/7 1.5V ≤ (V Minimum LT1584/5/7 1.5V ≤ (V
Load Current Quiescent Current LT1584/5/7-3.3 V
LT1584/5-3.38 V LT1584/5/7-3.45 V LT1584/5/7-3.6 V
IN IN IN IN
Ripple Rejection LT1584 f = 120Hz, C
LT1584-3.3 f = 120Hz, C LT1584-3.38 f = 120Hz, C LT1584-3.45 f = 120Hz, C LT1584-3.6 f = 120Hz, C LT1585 f = 120Hz, C
I
OUT
f = 120Hz, C I
OUT
LT1585-3.3 f = 120Hz, C
I
OUT
f = 120Hz, C I
OUT
LT1585-3.38 f = 120Hz, C LT1585-3.45 f = 120Hz, C LT1585-3.6 f = 120Hz, C LT1587 f = 120Hz, C LT1587-3.3 f = 120Hz, C LT1587-3.45 f = 120Hz, C LT1587-3.6 f = 120Hz, C
Thermal Regulation LT1584/5/7 TA = 25°C, 30ms pulse
LT1584/5/7-3.3 TA = 25°C, 30ms pulse LT1584/5-3.38 TA = 25°C, 30ms pulse LT1584/5/7-3.45 T
= 25°C, 30ms pulse
A
LT1584/5/7-3.6 TA = 25°C, 30ms pulse 0.004 0.02 %/W
Temperature Stability ● 0.5 % Long-Term Stability TA = 125°C, 1000 Hrs. 0.03 1.0 % RMS Output Noise TA = 25°C, 10Hz ≤ f ≤ 10kHz 0.003 %
(% of V
OUT
)
Thermal Resistance LT1584 T Package: Control Circuitry/Power Transistor 0.65/2.7 °C/W Junction to Case LT1585 T Package: Control Circuitry/Power Transistor 0.7/3.0 °C/W
LT1585 M Package: Control Circuitry/Power Transistor 0.7/3.0 °C/W LT1587 T Package: Control Circuitry/Power Transistor 0.7/3.0 °C/W LT1587 M Package: Control Circuitry/Power Transistor 0.7/3.0 °C/W
– V
IN IN
IN
) ≤ 3V, 10mA ≤ I
OUT
– V
) ≤ 5.75V, 10mA ≤ I
OUT
– V
) ≤ 5.75V ● 210 mA
OUT
OUT
≤ I
FULL LOAD
OUT
≤ I
FULL LOAD
● 0.2 5 µA
= 5V = 5V = 5V = 5V ● 813 mA
= 25µF Tant., (V
OUT
= 25µF Tant., VIN = 5.8V, I
OUT
= 25µF Tant., VIN = 5.88V, I
OUT
= 25µF Tant., VIN = 5.95V, I
OUT
= 25µF Tant., VIN = 6.1V, I
OUT
= 25µF Tant., (V
OUT
IN
IN
– V
– V
) = 2.5V, I
OUT
OUT
OUT
) = 3V,
OUT
OUT OUT
= 7A
= 7A = 7A
= 7A
OUT
= 7A
= 4.6A, TJ ≥ 25°C
= 25µF Tant., (V
OUT
IN
– V
OUT
) = 3V,
= 4A, TJ < 25°C
= 25µF Tant., VIN = 6.3V,
OUT
= 4.6A, TJ ≥ 25°C
= 25µF Tant., VIN = 6.3V,
OUT
= 4A, TJ < 25°C
= 25µF Tant., VIN = 6.38V, I
OUT
= 25µF Tant., VIN = 6.45V, I
OUT
= 25µF Tant., VIN = 6.6V, I
OUT
= 25µF Tant., (V
OUT
= 25µF Tant., VIN = 6.3V, I
OUT
= 25µF Tant., VIN = 6.45V, I
OUT
= 25µF Tant., VIN = 6.6V, I
OUT
IN
– V
OUT
= 4A
OUT
= 4A
OUT
= 4A
OUT
) = 3V, I
OUT
OUT
OUT
= 3A
OUT
= 3A
= 3A
= 3A ● 60 72 dB
The
● denotes specifications which apply over the specified operating
temperature range. Note 1: See thermal regulation specifications for changes in output voltage
due to heating effects. Load and line regulation are measured at a constant junction temperature by low duty cycle pulse testing.
Note 2: Line and load regulation are guaranteed up to the maximum power dissipation (25W for the LT1584 in T package, 26.5W for the LT1585 in T package, 18W for the LT1587 in T package). Power dissipation is determined by input/output differential and the output current. Guaranteed maximum output power will not be available over the full input/output voltage range.
4
Note 3: I
FULL LOAD
as a function of input-to-output voltage. I LT1584, 4.6A at T
is defined as the maximum value of output load current
≥ 25°C and 4A at TJ < 25°C for the LT1585/LT1585-3.3
J
FULL LOAD
is equal to 7A for the
and 3A for the LT1587. The remaining LT1585 fixed voltage versions are 4A.
The LT1585 and LT1587 have constant current limit with changes in input-to-output voltage. The LT1584 has variable current limit which decreases about 4A as input-to-output voltage increases from 3V to 7V.
W
TEMPERATURE (°C)
–0.20
OUTPUT VOLTAGE DEVIATION (%)
–0.10
0
0.10
–0.15
–0.05
0.05
–25 25 75 125
LT1584 • TPC03
175–50–75 0 50 100 150
∆I = 7A
TEMPERATURE (°C)
–0.20
OUTPUT VOLTAGE DEVIATION (%)
–0.10
0
0.10
–0.15
–0.05
0.05
–25 25 75 125
LT1584 • TPC03
175–50–75 0 50 100 150
∆I = 4.6A
TEMPERATURE (°C)
–0.20
OUTPUT VOLTAGE DEVIATION (%)
–0.10
0
0.10
–0.15
–0.05
0.05
–25 25 75 125
LT1584 • TPC09
175–50–75 0 50 100 150
∆I = 3A
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TYPICAL PERFORMANCE CHARACTERISTICS
LT1584/LT1585/LT1587
LT1584 Dropout Voltage vs Output Current
1.5 GUARANTEED
1.4 TEST POINTS
1.3
1.2
1.1
1.0
0.9
0.8
DROPOUT VOLTAGE (V)
0.7
0.6
0.5
0
2
1
OUTPUT CURRENT (A)
LT1585 Dropout Voltage vs Output Current
1.5 GUARANTEED
1.4
TEST POINTS
1.3
1.2
1.1
1.0
0.9
0.8
DROPOUT VOLTAGE (V)
0.7
0.6
0.5
1
0
2
OUTPUT CURRENT (A)
T = 25°C
3
T = 25°C
4
T = –5°C
T = 125°C
3
5
LTC1584 • TPC01
T = –5°C
T = 125°C
4
LT1585 • TPC04
LT1584 Short-Circuit Current vs Input/Output Differential
10
8
6
4
2
SHORT-CIRCUIT CURRENT (A)
0
7
6
0
T = 125°C T = 25°C T = –5°C 
2
1 INPUT/OUTPUT DIFFERENTIAL (V)
3
MINIMUM
4
5
LT1584 • TPC02
7
6
LT1585 Short-Circuit Current vs Temperature
6.0
5.5
5.0
4.5
SHORT-CIRCUIT CURRENT (A)
4.0 –50
–25
5
–75
50
0 TEMPERATURE (°C)
75
25
100
125
LT1584 • TPC05
150
175
LT1584 Load Regulation vs Temperature
LT1585 Load Regulation vs Temperature
LT1587 Dropout Voltage vs Output Current
1.5 GUARANTEED
1.4
TEST POINTS
1.3
1.2
1.1
1.0
0.9
0.8
DROPOUT VOLTAGE (V)
0.7
0.6
0.5
T = 25°C
T = 125°C
0
0.5
1.5 2.0
1.0
OUTPUT CURRENT (A)
T = –5°C
2.5
LT1584 • TPC07
3.0
LT1587 Short-Circuit Current vs Temperature
5.0
4.5
4.0
3.5
SHORT-CIRCUIT CURRENT (A)
3.0 –50
–75
–25
50
0
25
TEMPERATURE (°C)
LT1587 Load Regulation vs Temperature
75
100
125
175
150
LT1584 • TPC05
5
LT1584/LT1585/LT1587
TEMPERATURE (°C)
–75
OUTPUT VOLTAGE (V)
3.60
3.65
3.70
125
LT1584 • TPC12
3.55
3.50
3.45
3.40
3.35
3.30
3.25
3.20 –25
25
75
–50 150
0
50
100
175
V
OUT
= 3.6V
V
OUT
= 3.45V
V
OUT
= 3.38V
V
OUT
= 3.3V
TEMPERATURE (°C)
–75
QUIESCENT CURRENT (mA)
9
11
13
125
LT1584 • TPC15
7
5
8
10
12
6
4 3
–25
25
75
–50 150
0
50
100
175
W
U
TYPICAL PERFORMANCE CHARACTERISTICS
LT1584/5/7 Reference Voltage vs Temperature
1.275
1.270
1.265
1.260
1.255
1.250
1.245
1.240
REFERENCE VOLTAGE (V)
1.235
1.230
1.255 –25
–50 150
–75
0
25
50
TEMPERATURE (°C)
LT1584/5/7 Minimum Load Current vs Temperature
5
4
3
2
1
MINIMUM LOAD CURRENT (mA)
0
–25
–75
0
–50 150
25
50
TEMPERATURE (°C)
Output Voltage vs Temperature Using Adjustable LT1584/5/7
3.70 V
SET WITH 1% RESISTORS
OUT
3.65
3.60
3.55
3.50
3.45
3.40
3.35
OUTPUT VOLTAGE (V)
3.30
3.25
75
100
125
175
LT1584 • TPC10
3.20
–25
–75
–50 150
V
= 3.6V
OUT
V
= 3.45V
OUT
V
= 3.38V
OUT
V
= 3.3V
OUT
0 TEMPERATURE (°C)
75
25
50
100
125
LT1584 • TPC11
175
LT1584/5/7 Adjust Pin Current vs Temperature
100
90 80 70
60
50 40 30
ADJUST PIN CURRENT (µA)
20 10
0
–25
75
100
125
LT1584 • TPC13
175
–75
0
–50 150
TEMPERATURE (°C)
75
100
125
25
50
175
LT1584 • TPC14
LT1584/5/7-3.XX Output Voltage vs Temperature
LT1584/5/7-3.XX Quiescent Current vs Temperature
LT1584/5/7 Ripple Rejection vs Frequency
90
80
70
60
50
40
30
RIPPLE REJECTION (dB)
20
10
6
LT1584: (VIN – V LT1585/87: (V
0.5V ≤ V
= I
I
OUT
0
10 1k 10k 100k
RIPPLE
FULL LOAD
100
FREQUENCY (Hz)
IN
≤ 2V
OUT
– V
) ≤ 2.5V
) ≤ 3V
OUT
LT1584 • TPC16
LT1585/7 Maximum Power Dissipation*
30
LT1585
25
20
LT1587
15
POWER (W)
10
5
0
50
60 70
*AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE *AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE
90 110 120 130 140 150
80 100
CASE TEMPERATURE (˚C)
LT1584 • TPC17
LT1584 Maximum Power Dissipation*
30
25
20
15
POWER (W)
10
5
0
70 90 110 130
CASE TEMPERATURE (°C)
LT1584 • TPC18
1506050 80 100 120 140
WW
SI PLIFIED SCHE ATIC
V
IN
THERMAL
LIMIT
ADJ
GND
FOR FIXED VOLTAGE DEVICE
LT1584/LT1585/LT1587
+
–
V
OUT
LT1584 • BD
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APPLICATIONS INFORMATION
General
The LT1584/LT1585/LT1587 family of three-terminal regulators is easy to use and has all the protection features expected in high performance linear regulators. The de­vices are short-circuit protected, safe-area protected, and provide thermal shutdown to turn off the regulators should the junction temperature exceed about 150°C. The LT1584/LT1585/LT1587 family includes adjustable and fixed voltage versions.
These ICs are pin compatible with the LT1083/LT1084/ LT1085 family of linear regulators but offer lower dropout voltage and faster transient response. The trade-off for this improved performance is a 7V maximum supply voltage. Similar to the LT1083/LT1084/LT1085 family, the LT1584/ LT1585/LT1587 regulators require an output capacitor for stability. However, the improved frequency compensation permits the use of capacitors with much lower ESR while still maintaining stability. This is critical in addressing the needs of modern, low voltage, high speed microprocessors.
Current generation microprocessors cycle load current from almost zero to amps in tens of nanoseconds. Output voltage tolerances are tighter and include transient re­sponse as part of the specification. The LT1584/LT1585/
LT1587 family is specifically designed to meet the fast current load-step requirements of these microprocessors and saves total cost by needing less output capacitance in order to maintain regulation.
Stability
The circuit design in the LT1584/LT1585/LT1587 family requires the use of an output capacitor as part of the frequency compensation. For all operating conditions, the addition of a 22µF solid tantalum or a 100µF aluminum electrolytic on the output ensures stability. Normally, the LT1584/LT1585/LT1587 can use smaller value capacitors. Many different types of capacitors are available and have widely varying characteristics. These capacitors differ in capacitor tolerance (sometimes ranging up to ±100%), equivalent series resistance, equivalent series inductance, and capacitance temperature coefficient. The LT1584/ LT1585/LT1587 frequency compensation optimizes fre­quency response with low ESR capacitors. In general, use capacitors with an ESR of less than 1Ω.
On the adjustable LT1584/LT1585/LT1587, bypassing the adjust terminal improves ripple rejection and transient response. Bypassing the adjust pin increases the required output capacitor value. The value of 22µF tantalum or
7
LT1584/LT1585/LT1587
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APPLICATIONS INFORMATION
100µF aluminum covers all cases of bypassing the adjust terminal. With no adjust pin bypassing, smaller values of capacitors provide equally good results.
Normally, capacitor values on the order of several hundred microfarads are used on the output of the regulators to ensure good transient response with heavy load current changes. Output capacitance can increase without limit and larger values of output capacitance further improve the stability and transient response of the LT1584/LT1585/ LT1587 family.
Large load current changes are exactly the situation pre­sented by modern microprocessors. The load current step contains higher order frequency components that the output decoupling network must handle until the regulator throttles to the load current level. Capacitors are not ideal elements and contain parasitic resistance and inductance. These parasitic elements dominate the change in output voltage at the beginning of a transient load step change. The ESR of the output capacitors produces an instanta­neous step in output voltage (∆V = ∆I × ESR). The ESL of the output capacitors produces a droop proportional to the rate of change of output current (V = L × ∆I/∆t). The output capacitance produces a change in output voltage propor­tional to the time until the regulator can respond (∆V = ∆t × ∆I/C). These transient effects are illustrated in Figure 1.
ESR EFFECTS
network is actually inside the microprocessor socket cav­ity. In addition, use large power and ground plane areas to minimize distribution drops.
A possible stability problem that occurs in monolithic linear regulators is current limit oscillations. The LT1585/LT1587 essentially have a flat current limit over the range of input supply voltage. The lower current limit rating and 7V maximum supply voltage rating for these devices permit this characteristic. Current limit oscillations are typically nonexistent, unless the input and output decoupling ca­pacitors for the regulators are mounted several inches from the terminals. The LT1584 differs from the LT1585/ LT1587 and provides current limit foldback as input-to­output differential voltage increases. This safe-area char­acteristic exhibits a negative impedance because increas­ing voltage causes output current to decrease. Negative resistance during current limit is not unique to the LT1584 devices and is present on many power IC regulators. The value of the negative resistance is a function of how fast the current limit is folded back as input-to-output voltage increases. This negative resistance can react with capaci­tors and inductors on the input and output to cause oscillation during current limit. Depending on the values of series resistances, the overall system may end up unstable. However, the oscillation causes no problem and the IC remains protected. In general, if this problem occurs and is unacceptable, increasing the amount of output capacitance helps dampen the system.
ESL EFFECTS
SLOPE, =
V
∆I
t
C
POINT AT WHICH REGULATOR
TAKES CONTROL
Figure 1
CAPACITANCE EFFECTS
LT1584 • F01
The use of capacitors with low ESR, low ESL, and good high frequency characteristics is critical in meeting the output voltage tolerances of these high speed microprocessors. These requirements dictate a combination of high quality, surface mount tantalum capacitors and ceramic capaci­tors. The location of the decoupling network is critical to transient response performance. Place the decoupling network as close as possible to the processor pins because trace runs from the decoupling capacitors to the processor pins are inductive. The ideal location for the decoupling
8
Protection Diodes
In normal operation, the LT1584/LT1585/LT1587 family does not require any protection diodes. Older three-termi­nal regulators require protection diodes between the out­put pin and the input pin or between the adjust pin and the output pin to prevent die overstress.
On the adjustable LT1584/LT1585/LT1587, internal resis­tors limit internal current paths on the adjust pin. Therefore, even with bypass capacitors on the adjust pin, no protec­tion diode is needed to ensure device safety under short­circuit conditions.
A protection diode between the input and output pins is usually not needed. An internal diode between the input and output pins on the LT1584/LT1585/LT1587 family can
LT1584/LT1585/LT1587
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APPLICATIONS INFORMATION
handle microsecond surge currents of 50A to 100A. Even with large value output capacitors it is difficult to obtain those values of surge currents in normal operation. Only with large values of output capacitance, such as 1000µ F to 5000µ F, and with the input pin instantaneously shorted to ground can damage occur. A crowbar circuit at the input of the LT1584/LT1585/LT1587 can generate those levels of current, and a diode from output to input is then recom­mended. This is shown in Figure 2. Usually, normal power supply cycling or system “hot plugging and unplugging” will not generate current large enough to do any damage.
The adjust pin can be driven on a transient basis ±7V with respect to the output, without any device degradation. As with any IC regulator, exceeding the maximum input-to­output voltage differential causes the internal transistors to break down and none of the protection circuitry is then functional.
D1
1N4002
(OPTIONAL)
maximum supply voltage. When power is first applied, the input voltage rises and the output voltage follows the input. The input-to-output voltage remains small and the regula­tor can supply large output currents. This action permits the regulator to start-up into very heavy loads.
With higher input voltages, a problem can occur where the removal of an output short does not permit the output voltage to recover. This problem is not unique to the LT1584 devices and is present on the LT1083/LT1084/ LT1085 family and older generation linear regulators. The problem occurs with a heavy output load, a high input voltage, and a low output voltage. An example is immedi­ately after the removal of a short circuit. The load line of such a load may intersect the output current curve at two points. If this happens, two stable output operating points exist for the regulator. With this double intersection, the power supply may require cycling down to zero and back up again to make the output recover. This situation does not occur with the LT1585/LT1587 because no foldback circuitry is required to provide safe-area protection.
LT1584-3.3
V
IN
+
V
IN
+
C1 10µF
C1 10µF
IN OUT
GND
D1
1N4002
(OPTIONAL)
LT1584
IN OUT
ADJ
+
C
ADJ
Figure 2
V
C2 22µF
OUT
V
C2 22µF
LT1584 • F02
OUT
+
+
R1
R2
Overload Recovery
The LT1584 devices have safe-area protection similar to the LT1083/LT1084/LT1085. The safe-area protection de­creases current limit as input-to-output voltage increases. This behavior keeps the power transistor inside a safe operating region for all values of input-to-output voltage. The LT1584 protection circuitry provides some output current at all values of input-to-output voltage up to the 7V
Ripple Rejection
The typical curve for ripple rejection reflects values for the LT1584/LT1585/LT1587 fixed output voltage parts be­tween 3.3V and 3.6V. In applications that require improved ripple rejection, use the adjustable devices. A bypass capacitor from the adjust pin to ground reduces the output ripple by the ratio of V
/1.25V. The impedance of the
OUT
adjust pin capacitor at the ripple frequency should be less than the value of R1 (typically in the range of 100Ω to 120Ω) in the feedback divider network in Figure 2. There­fore, the value of the required adjust pin capacitor is a function of the input ripple frequency. For example, if R1 equals 100Ω and the ripple frequency equals 120Hz, the adjust pin capacitor should be 22µ F. At 10kHz, only 0.22µ F is needed.
Output Voltage
The LT1584/LT1585/LT1587 adjustable regulators develop a 1.25V reference voltage between the output pin and the adjust pin (see Figure 3). Placing a resistor R1 between these two terminals causes a constant current to flow through R1 and down through R2 to set the overall output voltage. Normally, this current is the specified minimum
9
LT1584/LT1585/LT1587
LT1584
OUTINV
IN
ADJ
R
P
PARASITIC
LINE RESISTANCE
R1*
*CONNECT R1 TO CASE CONNECT R2 TO LOAD
LT1584 • F05
R
L
R2*
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APPLICATIONS INFORMATION
load current of 10mA. The current out of the adjust pin adds to the current from R1 and is typically 55µA. Its output voltage contribution is small and only needs consideration when very precise output voltage setting is required.
V
IN
+
C1 10µF
V
= V
(1 + R2/R1) + I
OUT
REF
Figure 3. Basic Adjustable Regulator
Load Regulation
It is not possible to provide true remote load sensing because the LT1584/LT1585/LT1587 are three-terminal devices. Load regulation is limited by the resistance of the wire connecting the regulators to the load. Load regulation per the data sheet specification is measured at the bottom of the package.
IN
55µA
I
ADJ
LT1584
ADJ
ADJ
OUT
(R2)
V
V
REF
+
R1
R2
OUT
C2 22µF
LT1585 • F03
The connection shown in Figure 5 does not multiply RP by the divider ratio. As an example, RP is about four milliohms per foot with 16-gauge wire. This translates to 4mV per foot at 1A load current. At higher load currents, this drop represents a significant percentage of the overall regula­tion. It is important to keep the positive lead between the regulator and the load as short as possible and to use large wire or PC board traces.
Figure 5. Connection for Best Load Regulation
For fixed voltage devices, negative side sensing is a true
Thermal Considerations
Kelvin connection with the ground pin of the device re­turned to the negative side of the load. This is illustrated in Figure 4.
R
P
PARASITIC
LINE RESISTANCE
R
L
V
IN
LT1584-3.3
IN OUT
GND
The LT1584/LT1585/LT1587 family protects the device under overload conditions with internal power and thermal limiting circuitry. However, for normal continuous load conditions, do not exceed maximum junction temperature ratings. It is important to consider all sources of thermal resistance from junction-to-ambient. These sources in­clude the junction-to-case resistance, the case-to-heat sink interface resistance, and the heat sink resistance.
LT1585 • F04
Thermal resistance specifications have been developed to more accurately reflect device temperature and ensure safe
Figure 4. Connection for Best Load Regulation
operating temperatures. The electrical characteristics sec­tion provides a separate thermal resistance and maximum
For adjustable voltage devices, negative side sensing is a true Kelvin connection with the bottom of the output divider returned to the negative side of the load. The best load regulation is obtained when the top of resistor divider R1 connects directly to the regulator output and not to the load. Figure 5 illustrates this point. If R1 connects to the load, the effective resistance between the regulator and the load is:
RP × (1 + R2/R1), RP = Parasitic Line Resistance
junction temperature for both the control circuitry and the power transistor. Older regulators, with a single junction­to-case thermal resistance specification, use an average of the two values provided here and allow excessive junction temperatures under certain conditions of ambient tem­perature and heat sink resistance. Calculate the maximum junction temperature for both sections to ensure that both thermal limits are met.
Junction-to-case thermal resistance is specified from the IC junction to the bottom of the case directly below the die.
10
LT1584/LT1585/LT1587
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APPLICATIONS INFORMATION
This is the lowest resistance path for heat flow. Proper mounting ensures the best thermal flow from this area of the package to the heat sink. Linear Technology strongly recommends thermal compound at the case-to-heat sink interface. Use a thermally conductive spacer if the case of the device must be electrically isolated and include its contribution to the total thermal resistance. Please consult “Mounting Considerations for Power Semiconductors”
1990 Linear Applications Handbook, Volume I
RR3-1 to RR3-20. The output connects to the case of all devices in the LT1584/LT1585/LT1587 series.
For example, using an LT1585CT-3.3 (TO-220, commer­cial) and assuming:
VIN(Max Continuous) = 5.25V (5V + 5%), V I
= 4.6A
OUT
TA = 70°C, θ
θ
CASE-TO-HEAT SINK
HEAT SINK
= 4°C/W
= 1°C/W (with Thermal Compound)
, Pages
OUT
= 3.3V,
Power dissipation under these conditions is equal to:
PD = (V
IN
– V
OUT
)(I
) = (5.25 – 3.3)(4.6) = 9W
OUT
Junction temperature will be equal to:
TJ = TA + PD(θ
HEAT SINK
+ θ
CASE-TO-HEAT SINK
+ θJC)
For the Control Section:
TJ = 70°C + 9W (4°C/W + 1°C/W + 0.7°C/W) = 121.3°C
121.3°C < 125°C = T
(Control Section Commercial
JMAX
range)
For the Power Transistor:
TJ = 70°C + 9W (4°C/W + 1°C/W + 3°C/W) = 142°C 142°C < 150°C = T
(Power Transistor Commercial
JMAX
Range)
In both cases the junction temperature is below the maxi­mum rating for the respective sections, ensuring reliable operation.
U
TYPICAL APPLICATIONS N
Recommended LT1587-3.45 Circuit for the Intel 486TM DX4TM Overdrive Microprocessor
≥ 4.75V
IN
Minimum Parts Count LT1585 Adjustable Circuit
for the Intel Pentium VRE Processor
THERMALLOY
7020B-MT
4.75V TO
5.25V C1 TO C3
220µF
10V
AVX TPS
3 EACH
AVX X7R 0805
486 and DX4 are trademarks of Intel Corporation.
+
330nF
IN
LT1585CT
C4
16V
OUT
ADJ
C1
+
10µF 10V
IN
OUTV
LT1587-3.45
GND
R1 110Ω
0.1%
R2 197Ω
0.1%
+
AVX CORP. (803) 448-9411 THERMALLOY INC. (214) 243-4321
DO NOT SUBSTITUTE COMPONENTS.
PLACE AT MICROPROCESSOR SOCKET V
C2
+
22µF 10V
PLACE IN MICROPROCESSOR
SOCKET CAVITY
C5 TO C10 100µF 10V AVX TPS 4 EACH
C3 TO C6
+
47µF 10V
ESR OF THE 47µF IS <0.1Ω
C11 TO C20 1µF 16V AVX Y5V 0805 24 EACH
3.50V
4.6A
1584/5/7 TA04
C7 TO C15
0.1µF
PINS
CC
3.45V 3A
C16 TO C24
0.01µF
LT1584 • TA03
V
OUT
50mV/DIV
I
OUT
2A/DIV
LT1585 Transient Response for 3.8A Load Current Step*
100µs/DIV
*TRANSIENT RESPONSE MEASURED WITH AN INTEL
POWER VALIDATOR. V POWER VALIDATOR
IS MEASURED AT THE
OUT
LT1584 • TA05
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen­tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
11
LT1584/LT1585/LT1587
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TYPICAL APPLICATIONS N
Guaranteed LT1584/LT1431 Circuit for the Intel 90MHz and 100MHz Pentium Processors
(Meets Intel Specifications with Worst-Case Tolerances)
THERMALLOY
3
C1
0.1µF
NOTES: UNLESS OTHERWISE SPECIFIED
1. ALL RESISTOR VALUES ARE OHMS,  1/8W, 5%
2. ALL CAPACITORS ARE 50V, 20%
3. ALL POLARIZED CAPACITORS ARE AVX  TYPE TPS OR EQUIVALENT
4. INPUT CAPACITANCE MAY BE REDUCED  IF THE 5V SUPPLY IS WELL BYPASSED
5. FOR 100MHz PENTIUM PROCESSOR, INPUT VOLTAGE MUST BE AT LEAST
4.85V AT THE REGULATOR INPUT
6. FOR PENTIUM VRE PROCESSOR,  R4 NOT INSTALLED – FOR 3.3V OUTPUT, INSTALL 0Ω JUMPER RESISTOR R4
7. R3A TO R3E ARE B.I. TECHNOLOGY 627V100
5V
SEE NOTE 5
C2 TO C4
+
220µF 10V AVX TPS 3 EACH
7021B-MT
ADJ
1
33pF
NPO
OUT
C5
3
4
2
R1 1k
2
COMP COL
+
V
LT1431S
R
T
SGND FGND
56
REF
R
1
M
R2
1k
8
7
C6
0.01µF
SEE NOTE 6
R3D 83Ω
4
R3C 800Ω 
3
R3B
1.35k
2
 R3A
1.15k
1
IN
LT1584
LT1584/LT1431 Transient Response
for 3.8A Load Current Step*
R4
R3E
117Ω
SEE NOTE 7
SGND PGND
PLACE IN MICROPROCESSOR
SOCKET CAVITY
V
OUT
+
C7 100µF 10V
SENSE
PGND
LT1584 • TA06
65
+
C8 TO C13 100µF 10V AVX TPS 4 EACH
+
C14 TO C23 1µF 16V AVX Y5V 0805 24 EACH
V
OUT
50mV/DIV
*TRANSIENT RESPONSE
I
OUT
2A/DIV
100µs/DIV
LT1584 • TA07
MEASURED WITH AN INTEL POWER VALIDATOR. V
IS MEASURED AT THE
OUT
POWER VALIDATOR
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
LT1083/84/85 7.5A, 5A, 3A Low Dropout Linear Regulators Fixed Output at 3.3V, 3.6V, 5V and 12V, VIN to 25V LT1083/84/85 7.5A, 5A, 3A Low Dropout Linear Regulators Adjustable Output with up to 30V (VIN – V LT1086 1.5A Low Dropout Linear Regulator Both Fixed and Adjustable Versions, (VIN – V LT1521 300mA Low Dropout Linear Regulator with 12µA Quiescent Both Fixed and Adjustable Versions, Surface Mount
Current and Shutdown Package Available
LT1529 3A Low Dropout Linear Regulator with 50µA Quiescent Both Fixed and Adjustable Versions, Surface Mount
Current and Shutdown Package Available
LT1580 7A Very Low Dropout Linear Regulator 540mV Dropout at 7A, Remote Sensing
) Differential
OUT
) to 30V
OUT
12
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900
●
FAX
: (408) 434-0507
●
TELEX
: 499-3977
LT/GP 0395 10K • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 1995
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