TI PT8121

PT8120 Series
30-A 12-V Input Programmable
Integrated Switching Regulator
SLTS158B
(Revised 6/6/2002)
Features
•
•
•
•
Single Device: 30ADC
+12V-Input
High Efficiency: 92% @3.3V
Programmable Output:
(VRM Compatible 5-bit Codes)
• Multiphase Topology
• Output Remote Sense
• Over-Current Protection
Description
•
•
•
•
Thermal Shutdown
Standby On/Off Control
Space-Saving Package
Solderable Copper Case
Ordering Information
The PT8120 Excalibur™ power
modules are a family of high-output,
high-efficiency, fully integrated
switching regulators (ISRs), housed
in a solderable 31-pin space-saving
copper package. These modules
operate from a nominal input voltage
of +12V to provide up to 30A of
output current at output voltages as
low as 0.8V. The output voltage is
programmable via a 5-bit input code.
The PT8120 family incorporates
a state-of-the-art, 2-phase, multiple
power path topology. This extends
the output current range while providing superior transient response
and input current ripple performance.
The PT8120 family is designed
to power high-end computing and
signal processing applications, all of
which demand high output currents
at low supply voltages.
The modules have a number of
features to facilitate system integration. These include over-current
protection, thermal shutdown, an
on/off standby control, and an output
remote sense to compensate for
voltage drop between the regulator
and the load. In addition, the voltage programming codes for the
PT8121, PT8122, & PT8124 are
compatible with Intel’s® VRM
specifications.
PT8121H
PT8122H
PT8123H
PT8124H
PT8125H
=
=
=
=
=
1.3V
1.075V
0.8V
1.05V
4.5V
to 3.5V
to 1.85V
to 1.575V
to 1.825V
to 7.6V
PT Series Suffix (PT1234 x )
Case/Pin
Configuration
Vertical
Horizontal
SMD
Order
Suffix
N
A
C
Package
Code
(EKH)
(EKF)
(EKG)
(Reference the applicable package code drawing for
the dimensions and PC board layout)
PT812x Standard Application (See page 4 for PT8124 application schematic)
PROGRAMMING PINS
VID0
VID1
VID2
VID3
VID4
REMOTE SENSE
VID
Common
11
Lin
VIN
12–16
5
4
3
2
1
PT8120 Series
31
VOUT
23–30
(Except PT8124)
1µH
+
CIN
6
17–22
GND
STBY*
For technical support and more information, see inside back cover or visit www.ti.com
L
O
A
D
+
COUT
GND
Cin = Required 1500µF electrolytic
Cout = Required 660µF low ESR OS-Con®, or
1,200µF aluminum electrolytic
L in = Optional 1µH input choke
PT8120 Series
30-A 12-V Input Programmable
Integrated Switching Regulator
Pin-Out Information
(Except PT8124 †)
Pin Function
Pin Function
Pin Function
1
VID 0
12
Vin
22
GND
2
VID 1
13
Vin
23
Vout
3
VID 2
14
Vin
24
Vout
4
VID 3
15
Vin
25
Vout
5
VID 4
16
Vin
26
Vout
6
STBY *
17
GND
27
Vout
7
Do Not Connect
18
GND
28
Vout
8
Do Not Connect
19
GND
29
Vout
9
Do Not Connect
20
GND
30
Vout
10
Do Not Connect
21
GND
31
Remote Sense
11
VID Common
* For STBY pin:
Open
=Output Enabled
Ground =Output Disabled
† See page 4 for PT8124 pin-out
Output Voltage Programming Information
(Except PT8124)
PT8122
(VRM 9.0)
PT8121
(VRM 8.3/8.4)
VID 3
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
VID 2 VID 1 VID 0
1
1
1
1
1
0
1
0
1
1
0
0
0
1
1
0
1
0
0
0
1
0
0
0
1
1
1
1
1
0
1
0
1
1
0
0
0
1
1
0
1
0
0
0
1
0
0
0
VID 4=1
Vout
2.00V
2.10V
2.20V
2.30V
2.40V
2.50V
2.60V
2.70V
2.80V
2.90V
3.00V
3.10V
3.20V
3.30V
3.40V
3.50V
VID 4=0
Vout
1.30V
1.35V
1.40V
1.45V
1.50V
1.55V
1.60V
1.65V
1.70V
1.75V
1.80V
1.85V
1.90V
1.95V
2.00V
2.05V
VID 4=1
Vout
1.075V
1.100V
1.125V
1.150V
1.175V
1.200V
1.225V
1.250V
1.275V
1.300V
1.325V
1.350V
1.375V
1.400V
1.425V
1.450V
VID 4=0
Vout
1.475V
1.500V
1.525V
1.550V
1.575V
1.600V
1.625V
1.650V
1.675V
1.700V
1.725V
1.750V
1.775V
1.800V
1.825V
1.850V
PT8123
(Custom Code)
VID 4=1
Vout
0.800V
0.825V
0.850V
0.875V
0.900V
0.925V
0.950V
0.975V
1.000V
1.025V
1.050V
1.075V
1.100V
1.125V
1.150V
1.175V
VID 4=0
Vout
1.200V
1.225V
1.250V
1.275V
1.300V
1.325V
1.350V
1.375V
1.400V
1.425V
1.450V
1.475V
1.500V
1.525V
1.550V
1.575V
PT8125
(Custom Code)
VID 4=1
Vout
4.5V
4.6V
4.7V
4.8V
4.9V
5.0V
5.1V
5.2V
5.3V
5.4V
5.5V
5.6V
5.7V
5.8V
5.9V
6.0V
VID 4=0
Vout
6.1V
6.2V
6.3V
6.4V
6.5V
6.6V
6.7V
6.8V
6.9V
7.0V
7.1V
7.2V
7.3V
7.4V
7.5V
7.6V
Notes:
i) Logic 0 = Connect to VID Common
ii) Logic 1 = Open circuit (no pull-up resistors)
iii) VID3 and VID4 may not be changed while the unit is operating.
iv) See page 4 for PT8124 (VRM 8.5) programming information.
For technical support and more information, see inside back cover or visit www.ti.com
PT8120 Series
30-A 12-V Input Programmable
Integrated Switching Regulator
PT8121 /2 /3 /5 Specifications
(Unless otherwise stated T a =25°C, C in =1,500µF, Cout =660µF, V in =12V, & Io = Iomax )
PT8121 /2 /3 /5 Only
Characteristics
Symbols
Output Current
Io
Conditions
Natural convection or
60°C with 200LFM airflow
Min
Vo ≤3.5V
Vo ≥4.5V
0.1
0.1
(1)
(1)
Typ
Max
Units
—
—
30
28
A
V
Input Voltage Range
Vin
Over Io Range
10.8
—
13.2
Set-Point Voltage Tolerance
Vo tol
Over Vo range
—
±1
±2
%V
Line Regulation
∆Reg line
Over Vin range
—
±10
—
mV
Load Regulation
∆Regload
Over Io range
—
±10
—
mV
Temperature Variation
∆Reg temp
–40°C ≤T a ≤85°C
—
±0.5
—
%Vo
Total Output Voltage Variation
∆Votot
Includes set-point, line load,
–40°C ≤Ta ≤ 85°C
—
—
±3
%V
Efficiency
η
Io =15A
Vo =5.0V
Vo =3.3V
Vo =2.5V
Vo =1.8V
Vo =1.5V
Vo =1.2V
—
—
—
—
—
—
94
92
90
86
84
81
—
—
—
—
—
—
%
=5.0V
=3.3V
=2.5V
=1.8V
=1.5V
=1.2V
—
—
—
—
—
—
93
91
88
84
82
78
—
—
—
—
—
—
%
mV
Io =I omax
Vo
Vo
Vo
Vo
Vo
Vo
Vo Ripple (pk-pk)
Vr
20MHz bandwidth
—
20
—
Transient Response
ttr
1A/µs load step, 50% to 100% Iomax
—
50
—
µSec
∆Vtr
Vo over/undershoot
—
100
—
mV
Over-Current Threshold
I TRIP
Reset followed by auto-recovery
—
—
40
45
—
—
A
Switching Frequency
ƒs
Over load range
300
350
400
kHz
—
—
0.5
Open (2)
0.8
—
35
—
mA
—
30,000
µF
—
—
µF
—
+85 (5)
°C
Vo ≥4.5V
Vo ≤3.5V
Standby Control (pin 6)
Input High Voltage
Input Low Voltage
Input Low Current
Referenced to GND (pins 17–22)
VIH
VIL
I IL
Pin 6 to GND
—
-0.2
—
Standby Input Current
Iin standby
Pin 6 to GND
—
External Output Capacitance
Cout
See PT812x application schematic
660
External Input Capacitance
C in
See PT812x application schematic
1,500
Operating Temperature Range
Ta
Over Vin Range
–40
Storage Temperature
Ts
—
-40
—
+125
°C
Mechanical Shock
Per Mil-STD-883D, Method 2002.3
1 msec, Half Sine, mounted to a fixture
—
500
—
G’s
Mechanical Vibration
Mil-STD-883D, Method 2007.2
20-2000 Hz, soldered in PCB
—
20 (6)
—
G’s
—
55
—
grams
Weight
—
Vertical/Horizontal
Flammability
—
Materials meet UL 94V-0
(3)
(4)
V
mA
Notes: (1) ISR-will operate down to no load with reduced specifications.
(2) The Standby input (pin 6) has an internal pull-up. If it is left open-circuit the PT812x will operate when input power is applied. A low-leakage
MOSFET is recommended to control this input. The open-circuit voltage is nominally 5V. See application notes for interface considerations.
(3) The PT8120 regulators require a minimum of 660µF, low ESR ouput capacitance (1,200µF for standard aluminum electrolytic) for proper operation.
(4) For operation below 0°C, Cout must have stable characteristics. Use either low ESR tantalum or Oscon® capacitors.
(5) See safe Operating Area curves or consult factory for the appropriate derating.
(6) The case pins on the through-hole package types (suffixes N & A) must be soldered. For more information see the applicable package outline drawing.
Input Filter: An input filter inductor is optional for most applications. The inductor must be rated to handle the projected input current. A rating of 10ADC for
Vout ≤3.3V, and 15ADC for V out ≥4.5V is recommended. The input capacitance must be rated for a minimum of 1.6Arms of ripple current. For transient or dynamic
load applications, additional capacitance may be required. For more information consult the application note on capacitor selection.
For technical support and more information, see inside back cover or visit www.ti.com
PT8120 Series
30-A 12-V Input Programmable
Integrated Switching Regulator
PT8124 Voltage Programming Information
PT8124 Pin-Out Information
(VRM 8.5)
Pin Function
Pin Function
1
VID 25mV
17
GND
2
VID 0
18
GND
3
VID 1
19
GND
4
VID 2
20
GND
5
VID 3
21
GND
6
STBY
22
GND
7
Do Not Connect
23
Vout
8
Do Not Connect
24
Vout
9
Do Not Connect
25
Vout
10
Do Not Connect
26
Vout
11
VID Common
27
Vout
12
Vin
28
Vout
13
Vin
29
Vout
14
Vin
30
Vout
15
Vin
31
Remote Sense
16
Vin
VID 3
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
* For STBY pin:
Open
=Output Enabled
Ground =Output Disabled
VID 2 VID 1 VID 0
1
1
1
1
1
0
1
0
1
1
0
0
0
1
1
0
1
0
0
0
1
0
0
0
1
1
1
1
1
0
1
0
1
1
0
0
0
1
1
0
1
0
0
0
1
0
0
0
VID 25mV=0
Vout
1.300V
1.350V
1.400V
1.450V
1.500V
1.550V
1.600V
1.650V
1.700V
1.750V
1.800V
1.050V
1.100V
1.150V
1.200V
1.250V
VID 25mV=1
Vout
1.325V
1.375V
1.425V
1.475V
1.525V
1.575V
1.625V
1.675V
1.725V
1.775V
1.825V
1.075V
1.125V
1.175V
1.225V
1.275V
Notes:
i) Logic 0 = Connect to VID Common
ii) Logic 1 = Open circuit (no pull-up resistors)
iii) VID2 and VID3 may not be changed while the unit is operating.
PT8124 Standard Application
PROGRAMMING PINS
VID 25mV
VID 0
VID 1
VID 2
VID 3
REMOTE SENSE
VID
Common
11
Lin
VIN
3
2
1
31
VOUT
23–30
(Only)
1µH
+
STBY*
4
PT8124
12–16
CIN
GND
5
6
17–22
L
O
A
D
+
COUT
GND
Cin = Required 1500µF electrolytic
Cout = Required 660µF low ESR OS-Con®, or
1,200µF aluminum electrolytic
L in = Optional 1µH input choke
For technical support and more information, see inside back cover or visit www.ti.com
PT8120 Series
30-A 12-V Input Programmable
Integrated Switching Regulator
PT8124 Specifications
(Unless otherwise stated T a =25°C, Cin =1,500µF, C out =660µF, Vin =12V, & I o = I omax )
PT8124 Only
Characteristics
Symbols
Conditions
Min
Output Current
Io
Natural convection or
60°C with 200LFM airflow
Typ
Max
Units
0.1
—
30
A
Input Voltage Range
Vin
Over Io Range
Set-Point Voltage Tolerance
Vo tol
Over Vo range, I o =0.5A
10.8
—
13.2
V
—
±1
±2
Line Regulation
∆Reg line
Over Vin range
%V
—
±10
—
mV
Load Regulation (Droop)
∆Regload
Over Io range
—
2
—
mV/A
Temperature Variation
∆Reg temp
–40°C ≤Ta ≤85°C, , Io =0.5A
—
±0.5
—
%Vo
Total Output Voltage Variation
∆Votot
Includes set-point, line, load
–40°C ≤Ta ≤ 85°C
—
—
85 (2)
mV
Efficiency
η
Io =15A
Vo =1.8V
Vo =1.5V
Vo =1.2V
—
—
—
86
84
81
—
—
—
%
Io =I omax
Vo =1.8V
Vo =1.5V
Vo =1.2V
—
—
—
84
82
78
—
—
—
%
mV
(1)
Vo Ripple (pk-pk)
Vr
20MHz bandwidth
—
20
—
Transient Response
ttr
1A/µs load step, 50% to 100% Iomax
—
50
—
µSec
∆Vtr
Vo over/undershoot
—
50
—
mV
Over-Current Threshold
I TRIP
Reset followed by auto-recovery
—
47
—
A
Switching Frequency
ƒs
Over load range
300
350
400
kHz
Standby Control (pin 6)
Input High Voltage
Input Low Voltage
Input Low Current
VIH
VIL
I IL
Pin 6 to GND
—
-0.2
—
—
—
0.5
Open (3)
0.8
—
Standby Input Current
Iin standby
Pin 6 to GND
—
35
—
mA
External Output Capacitance
Cout
See PT8124 application schematic
660
—
30,000
µF
External Input Capacitance
C in
See PT8124 application schematic
1,500
—
—
µF
Operating Temperature Range
Ta
Over Vin Range
–40
—
+85 (6)
°C
Storage Temperature
Ts
—
-40
—
+125
°C
Mechanical Shock
Per Mil-STD-883D, Method 2002.3
1 msec, Half Sine, mounted to a fixture
—
500
—
G’s
Mechanical Vibration
Mil-STD-883D, Method 2007.2
20-2000 Hz, soldered in PCB
—
20 (7)
—
G’s
—
55
—
grams
Referenced to GND (pins 17–22)
Weight
—
Vertical/Horizontal
Flammability
—
Materials meet UL 94V-0
(4)
(5)
V
mA
Notes: (1) ISR-will operate down to no load with reduced specifications.
(2) Total output voltage variation includes load regulation droop, which is required for compliance with specification VRM 8.5-4
(3) The Standby input (pin 6) has an internal pull-up. If it is left open-circuit the PT812x will operate when input power is applied. A low-leakage
MOSFET is recommended to control this input. The open-circuit voltage is nominally 5V. See application notes for interface considerations.
(4) The PT8120 regulators require a minimum of 660µF, low ESR ouput capacitance (1,200µF for standard aluminum electrolytic) for proper operation.
(5) For operation below 0°C, Cout must have stable characteristics. Use either low ESR tantalum or Oscon® capacitors.
(6) See safe Operating Area curves or consult factory for the appropriate derating.
(7) The case pins on the through-hole package types (suffixes N & A) must be soldered. For more information see the applicable package outline drawing.
Input Filter: An input filter inductor is optional for most applications. The inductor must be rated to handle the projected input current. A rating of 10ADC for
Vout ≤3.3V, and 15ADC for V out ≥4.5V is recommended. The input capacitance must be rated for a minimum of 1.6Arms of ripple current. For transient or dynamic
load applications, additional capacitance may be required. For more information consult the application note on capacitor selection.
For technical support and more information, see inside back cover or visit www.ti.com
PT8120 Series
30-A 12-V Input Programmable
Integrated Switching Regulator
Characteristic Data; Vin =12V
Safe Operating Area; Vin =12V
(See Note A)
Efficiency vs Output Current
PT8120 Series, Vout =5V
90
100
VOUT
80
Ambient Temperature (°C)
90
Efficiency - %
(See Note B)
5V
3.3V
2.5V
1.8V
1.5V
1.2V
1.0V
0.8V
80
70
Airflow
70
400LFM
200LFM
120LFM
60LFM
Nat conv
60
50
40
30
60
20
0
6
12
18
24
0
30
6
12
Iout (A)
Output Ripple vs Output Current
24
30
PT8120 Series, Vout =3.3V
90
25
80
VOUT
5V
0.8V
3.3V
1.5V
15
10
Ambient Temperature (°C)
30
20
Ripple - mV
18
Iout (A)
5
Airflow
70
Nat conv
60LFM
120LFM
200LFM
400LFM
60
50
40
30
0
20
0
6
12
18
24
0
30
6
12
Iout (A)
18
24
30
Iout (A)
Power Dissipation vs Output Current
PT8120 Series, Vout =1.5V
15
90
Pd - Watts
VOUT
5V
3.3V
1.5V
0.8V
9
6
3
Ambient Temperature (°C)
80
12
Airflow
70
400LFM
200LFM
120LFM
60LFM
Nat conv
60
50
40
30
0
20
0
6
12
18
Iout (A)
24
30
0
6
12
18
24
30
Iout (A)
Note A: Characteristic data has been developed from actual products tested at 25°C. This data is considered typical data for the Converter.
Note B: SOA curves represent the conditions at which internal components are at or below the manufacturer’s maximum operating temperatures
For technical support and more information, see inside back cover or visit www.ti.com
Application Notes
PT8120 Series & PT8139
Capacitor Recommendations for the
PT8120 Series of Programmable ISRs
Input Capacitors
The recommended input capacitor(s) is determined by
1.6 Arms minimum ripple current rating and 1,500µF
minimum capacitance. Ripple current and Equivalent
Series Resistance (ESR) values are the major considerations
along with temperature when selecting the proper capacitor. The tantalum capacitors listed below cannot be used
on the input bus since they are not rated for 12V operation.
Output Capacitors
The minimum required output capacitance is 660µF
(organic/polymer), or 1,200 (aluminum electrolytic) with
a maximum ESR less than or equal to 50mΩ. Failure to
observe this requirement may lead to regulator instability or oscillation. Electrolytic capacitors have poor ripple
performance at frequencies greater than 400kHz, but
excellent low frequency transient response. Above the
ripple frequency ceramic decoupling capacitors are necessary to improve the transient response and reduce any
microprocessor high frequency noise components apparent
during higher current excursions. Preferred low ESR type
capacitor part numbers are identified in the Table 1 below.
Tantalum Characteristics
Tantalum capacitors are recommended on the output bus
but only AVX TPS Series, Sprague 593D/594/595 Series,
or Kemet T495/T510,520 Series. These capacitors are
recommended over other types due to their higher surge
current, excellent power dissipation and ripple current
ratings. As a caution, the TAJ Series by AVX is not recommended. This series exhibits considerably higher ESR,
reduced power dissipation and lower ripple current capability. The TAJ Series is also less reliable compared to the
TPS series when determining power dissipation capability.
Capacitor Table
Table 1 identifies the characteristics of capacitors from a
number of vendors with acceptable ESR and ripple current
(rms) ratings. The suggested minimum quantities per
regulator for both the input and output buses are identified.
This is not an extensive capacitor list. Capacitors from
other vendors are available with comparable specifications.
Those listed are for guidance. The RMS ripple current rating
and ESR (Equivalent Series Resistance at 100kHz) are the
critical parameters are necessary to insure both optimum
regulator performance and long capacitor life.
Table 1 Capacitors Characteristic Data
Capacitor Vendor/
Series
Capacitor Characteristics
Quantity
Working
Voltage
Value(µF)
(ESR) Equivalent
Series Resistance
105°C Maximum
Ripple
Current(Irms)
Physical
Size(mm)
Input
Bus
Output
Bus
Vendor Part Number
Panasonic
FC (Radial)
35V
25V
1500
1500
0.028Ω
0.029Ω
2490mA
2205mA
18× 20
16× 20
1
1
1
1
EEUFC1V152S
EEUFC1E152S
FC/FK (Surface Mount)
16V
25V
16V
4700
2200
2200
0.033Ω
0.028Ω
0.038Ω
2060mA
2490mA
2000mA
18×16.5
18×21.5
18×16.5
1
1
2
1
1
1
EEVFK1C472M
EEVFC1E222N
EEVFC1C222N
United Chemi-con
LXZ Series
35V
25V
16V
1800
1800
2700
0.028Ω
0.029Ω
0.029Ω
2490mA
2210mA
2210mA
18× 20
16×20
16× 20
1
1
1
1
1
1
LXZ35VB182M18X20LL
LXZ25VB182M16X20LL
LXZ16VB272M16X20LL
Nichicon
PW Series
25V
25V
1000
1800
0.038÷2Ω
0.029Ω
3200mA
2205mA
12.5x20
16x20
2
1
1
1
UPW1E102MHH
UPW1E182MHH6
PM Series
25V
1500
0.034Ω
1770mA
16×20
1
1
UPM1E152MHH6
Os-con:( Organic)
SS
SV (Surface Mount)
10V
10V
330
330
0.025Ω
0.020Ω
3500mA
3800mA
10×10.5
10.3×10.3
N/R(1)
N/R(1)
2
2
10SS330M (Vo<6V)
10SV330 (Vo<6V)
AVX Tantalum
TPS (Surface Mount)
10V
10V
330
330
0.1Ω÷2 =0.05Ω
0.06Ω÷2 =0.03Ω
>2500mA
>3000mA
7.3L
×5.7W
×4.1H
N/R(1)
N/R(1)
2
2
TPSE337M010R0100 (Vo<5V)
TPSV337M010R0060( Vo<5V)
Kemet
Polymer/Tantalum
T520Series
(Surface Mount)
10V
10V
330
330
0.040÷2Ω
0.040÷2Ω
1800mA
>1800mA
4.3W
×7.3L
×4.0H
N/R(1)
N/R(1)
2
2
T520X337M010AS (Vo<6V)
T520D330M006AS (Vo<4V)
Sprague Tantalum
594D Series
(Surface Mount)
10V
330
0.045÷2Ω
2360mA
7.2L
×6W
×4.1H
N/R(1)
2
594D337X0010R2T(Vo<5V)
Note: (N/R -Not recommended) The 10V-rated tantalum capacitors cannot be used on the input bus.
For technical support and more information, see inside back cover or visit www.ti.com
Application Notes
PT8120 Series & PT8139
Using the On/Off Standby Function of the
PT8120 Series of Programmable ISRs
The PT8120 series of programmable ISRs incorporates
an On/Off Standby function. This feature may be used
to turn the regulated output of the module off while input
voltage is applied. This places the module in “standby”
mode. The standby control may be used for power-up
sequencing, or wherever there is a requirement to control
the module’s output status from another circuit.
2. In the standby mode the output of the regulator is tristate, and the output voltage falls at the rate that the
load circuit discharges the output filter capacitors.
3. When the ground signal to the Standby pin is
removed, the regulator output initiates a soft-start
cycle by first asserting a low impedance to ground. If
an external voltage is applied to the output bus, it will
sink current and possibly over-stress the part.
The Standby function is provided by the STBY* control,
pin 6. If pin 6 is left open-circuit the regulator operates
normally, providing a regulated output when a valid supply voltage is applied to Vin (pins 10-16) with respect to
GND (pins 17-22). Connecting pin 6 to ground 1 places
the regulator in standby mode 2, and reduces the input
current to typically 35mA. Applying a ground signal to
pin 6 prior to power-up, will inhibit the output during
the period that input power is applied. When the ground
signal to pin 6 is removed, the regulator initiates a softstart to re-establish the set output voltage. 3 To ensure
that the regulator output is properly enabled, the STBY*
control pin must be open circuit.
Table 1 Standby Control Requirements 2
Parameter
Min
Typ
V IH
—
V IL
–0.2V
Turn-On Time
Turning Q 1 in Figure 1 off, removes the low-voltage
signal at pin 6. After approximately 5-ms the regulator
output rises and reaches full regulation within 40ms.
Fig. 2 shows the typical waveforms of a PT8121 following
the prompt turn-off of Q1. The turn-off of Q1 corresponds
to the rise in Vstby. The output voltage was set to 3.3V,
and the waveforms were measured with a 12V input source,
and 18A resistive load.
Figure 2
Max
Open Cct. 1
—
I STBY
0.8V
–0.5mA
Vo (1V/Div)
Notes:
1. The standby on a PT8120 series regulators must be
controlled with an open-collector (or open-drain)
transistor (See fig. 1). Do Not use a pull-up resistor.
Table 1 gives the STBY* pin parameters. The control
pin has an open-circuit voltage of 5Vdc. To shut the
regulator output off, the control pin must be “pulled” to
less than 0.8Vdc with a low-impedance sink to ground.
Iin (5A/Div)
Vstby (5V/Div)
HORIZ SCALE: 5ms/Div
Figure 1
VO SENSE
11
VIN
VID
Common
Lin
12–16
1µH
CIN
STBY
6
1 =Off
GND
Q1
BSS138
4
3
2
VID4 – VID0
PT8121
V IN
+
5
1
31
Sense
VOUT
VO =3.3V
23–30
GND
17–22
L
O
A
D
+
COUT
GND
For technical support and more information, see inside back cover or visit www.ti.com
Application Notes
PT8120 Series & PT8139
Pin-Coded Output Voltage Programming of the
30-A Rated PT8120 Series Regulators
4. If active devices are used to ground the voltage control
pins, low-level open drain MOSFETs should be used over
bipolar transistors. The inherent Vce(sat) in bipolar devices
introduces errors in the device’s internal voltage control
circuit. Discrete transistors such as the BSS138, 2N7002,
IRLML2402, are examples of appropriate devices.
The PT8120 series of Excalibur® ISRs incorporate a
pin-coded output voltage control. These regulators must
be programmed to a specific output voltage from a preset range defined by the regulator model. Programming
is achieved by selectively connecting the control inputs,
“VID0–VID4” (pins 1–5), to the “VID Common” (pin 11). 1
The programming code and voltage range for each model
is defined in the data sheet. Refer to the PT8120 Series
data sheet for more information. The program codes for
the PT8121, PT8122, and PT8124 models are also compatible with some of the “Voltage ID” codes defined by
Intel’s® VRM specifications. Figure 1 shows the pin-strap
connections for selecting the desired output voltage from
the program code range.
Active Voltage Programming:
Special precautions should be taken when making changes
to the voltage control progam code while the output is
active. It is recommended that the ISR be powered down
or held placed in standby. Changes made to the program
code while Vout is active induces high current transients
through the device. This is the result of the electrolytic
output capacitors being either charged or discharged to the
new output voltage set-point. The transient current can be
minimized by making only incremental changes to the
binary code, i.e. one LSB at a time. A minimum of 100µs
settling time between each program state is also recommended. Making non-incremental changes to VID3 and
VID4 with the output enabled is discouraged. The transients induced may activate the module’s over-current
protection. If the program code cannot be asserted prior
to power-up, pull pin 6, STBY*, to GND during the
period that the input voltage is applied. The release of
pin 6 will then to allow the device to initiate a soft-start
power-up to the program voltage.
Notes:
1. The programming convention is as follows:Logic 0:
Connect to pin 11 (VID Common).
Logic 1:
Open circuit/open drain (See notes 2, & 4)
2. Do not connect pull-up resistors to the voltage
programming pins.
3. To minimize output voltage error, use pin 11 (VID
Common) as the logic “0” reference. If the regulator is
used to power a VRM compatible microprocessor this
may not be practical. In this case connect pin 11 to pins
17–22, or the ground plane close to the regulator.
Figure 1
VID0
VID1
VID2
VID3
VO SENSE
VID4
11
VIN
5
Lin
12–16
1µH
3
2
1
6
31
Sense
PT8121
VIN
STBY
+
4
VID4 – VID0
VID
Common
VOUT
VO =2.5V
23–30
GND
17–22
CIN
GND
For technical support and more information, see inside back cover or visit www.ti.com
L
O
A
D
+
COUT
GND
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