ON NCP1592 3 v to 6 v input, 6 a output synchronous buck pwm switcher with integrated fet Datasheet

NCP1592
3 V to 6 V Input, 6 A Output
Synchronous Buck PWM
Switcher with Integrated
FETs
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NCP1592 is a low input voltage 6 A synchronous buck converter
that integrates both 30 mW high side and low side MOSFETs.
NCP1592 is designed for space sensitive and high efficiency
applications. The main features include: a high performance voltage
error amplifier; an under−voltage−lockout circuit to prevent start−up
until the input voltage reaches 3 V; an internally or externally
programmable soft−start circuit to limit inrush currents; and a power
good output monitor signal. NCP1592 is available in thermally
enhanced 28−pin TSSOP package.
MARKING
DIAGRAM
TSSOP−28 EP
CASE 948BG
Features
A
L
Y
W
G
•
•
•
•
•
•
Application
• Low−Voltage, High−Density Distributed Power Systems
• High Performance Point of Load Regulation for DSPs, FPGAs,
•
•
ASICs and Microprocessors
Broadband, Networking and Optical Communications Infrastructure
Portable Computing/Notebook PCs
Input
= Assembly Location
= Wafer Lot
= Year
= Work Week
= Pb−Free Package
EFFICIENCY
• 30 mW, 12 A Peak MOSFET Switches for High to Efficiency at 6 A
Continuous Output Source or Sink Current
Adjustable Output Voltage Down to 0.891 V With 1.0% Accuracy
Wide PWM Frequency: Fixed 350 kHz, 550 kHz or Adjustable
280 kHz to 700 kHz
Synchronizable to 700 kHz
Load Protected by Peak Current Limit and Thermal Shutdown
Integrated Solution Reduces Board Area and Component Count
This is a Pb−Free Device
1592G
ALYW
VI = 5 V,
VO = 3.3 V
LOAD CURRENT (A)
Figure 1. Efficiency at 350 kHz
VIN
Output
PH
NCP1592
ORDERING INFORMATION
BOOT
See detailed ordering and shipping information in the package
dimensions section on page 18 of this data sheet.
PGND
VBIAS
AGND
VSENSE
COMP
Figure 2. Typical Application Circuit
© Semiconductor Components Industries, LLC, 2012
July, 2012 − Rev. 1
1
Publication Order Number:
NCP1592/D
SS/ENA
NCP1592
VIN
−
+
Enable
Comparator
2.5 ms
Falling
and
Rising
Edge
Deglitch
Thermal
Shutdown
150C
Falling
Edge
Deglitch
Figure 3. Typical Application Circuit
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2
VSENSE
Reference
Vref = 0.891V
(Internal Slow−Start Time = 3.35 ms)
Internal/External
Slow−start
−
Hysteresis 160 mV 2.5 ms
2.95 V
Hysteresis 30 mV
VIN UVLO
Comparator
VIN
+
1.2 V
5 mA
COMP
Error
Amplifier
_
+
SS_DIS
RT
OSC
PWM
Comparator
+
−
SHUTDOWN
SYNC
REG
ILIM
Comparator
−
+
VIN
SHUTDOWN
Powergood
Comparator
S
R Q
PH
Adaptive Dead−Time
and
Control Logic
SHUTDOWN
Hysteresis 30 mV
0.9*Vref
VSENSE
100 ns
Leading
Edge
Blanking
VBIAS
VBIAS
−
+
AGND
35 ms
Falling
Edge
Deglitch
30 mW
30 mW
PWRGD
PGND
PH
BOOT
VIN
LOUT
CO
3V − 6V
Vo
NCP1592
BLOCK DIAGRAM
NCP1592
AGND
1
28
RT
VSENSE
2
27
SYNC
COMP
3
26
SS/ENA
PWRGD
4
25
VBIAS
BOOT
5
24
VIN
PH
6
23
VIN
PH
7
22
VIN
PH
8
21
VIN
PH
9
20
VIN
PH
10
19
PGND
PH
11
18
PGND
PH
12
17
PGND
PH
13
16
PGND
14
15
PGND
PH
Thermal
PAD
(Top View)
Figure 4. Pin Connections
PIN DESCRIPTION
Pin No.
Symbol
Description
1
AGND
2
VSENSE
3
COMP
4
PWRGD
5
BOOT
6 ~ 14
PH
15 ~ 19
PGND
Power ground. High current return for the low−side driver and power MOSFET. Connect PGND with large
copper areas to the input and output supply returns, and negative terminals of the input and output capacitors.
A single point connection to AGND is recommended.
20 ~ 24
VIN
Input supply for the power MOSFET switches and internal bias regulator . Bypass VIN pins to PGND with X5R
or higher quality 10 mF ceramic capacitors.
25
VBIAS
Internal bias voltage output. 0.1 mF ~ 1.0 mF low ESR ceramic capacitor is recommended to connect between
VBIAS to AGND.
26
SS/ENA
Soft start/enable input/output. Dual function pin which provides logic input to enable/disable device operation
and capacitor input to externally set the start−up time.
27
SYNC
Synchronization input. Dual function pin which provides logic input to synchronize to an external oscillator or
pin select between two internally set switching frequencies. When used to synchronize to an external signal, a
resistor must be connected to the RT pin.
28
RT
Frequency setting resistor input. Connect a resistor from RT to AGND to set the switching frequency. When
using the SYNC pin, set the RT value for a frequency at or slightly lower than the external oscillator frequency.
Analog ground. Return for compensation network/output divider, slow−start capacitor. VBIAS capacitor, RT
resistor, and SYNC pin. Connect PowerPAD to AGND.
Error amplifier inverting input. Connect to output voltage through compensation network/output divider.
Error amplifier output. Connect frequency compensation network from COMP to VSENSE.
Power good open drain output. High when VSENSE ≥ 90% Vref otherwise PWRGD is low. Note that output is
low when SS/ENA is low or the internal shutdown signal is active.
Bootstrap output. 0.022 mF ~ 0.1 mF ceramic capacitor is recommended to connect between BOOT and PH
generates floating drive for the high−side FET drive.
Phase output. Junction of the internal high−side and low−side power MOSFETs, and output inductor.
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NCP1592
MAXIMUM RATINGS Over operating free−air temperature range unless otherwise noted
Rating
Symbol
Min
Max
Unit
VIN
−0.3
7
V
SS / ENA
−0.3
7
V
SYNC
−0.3
7
V
RT
−0.3
6
V
VSENSE
−0.3
4
V
High side drive supply voltage
BOOT
−0.3
PH+7
V
Output voltage range
VBIAS
−0.3
7
V
Compensation Voltage
COMP
−0.3
7
V
Power Good open collector voltage
PWRGD
−0.3
7
V
Power Switching Node Transient voltage excursion
PH
(Note 4)
−3
10
V
Internally Limited
A
Main supply voltage input
Soft start and enable voltage
Synchronization voltage
Frequency setting voltage
Output divided voltage sense
Power Switching Node Source current
PH
Compensation Source current
COMP
0
6
mA
Regulated voltage Source current
VBIAS
0
6
mA
Power Switching node sink current
PH
0
12
A
Compensation Sink current
COMP
0
6
mA
Soft start and enable Sink current
SS/ENA
0
10
mA
Power Good open collector Sink current
PWRGD
0
10
mA
Voltage differential
AGND to
PGND
−0.3
0.3
V
Operating Junction Temperature Range (Note 1)
TJ
−40
150
°C
Operating Ambient Temperature Range
TA
−40
85
°C
Storage Temperature Range
Tstg
−55
150
°C
Thermal Characteristics (Note 2)
TSSOP 28−pin EP Plastic Package
Maximum Power Dissipation @ TA = 25°C
Thermal Resistance Junction−to−Air with Solder
Thermal Resistance Junction−to−Air without Solder
PD
RqJA
RqJA
5.49
18.2
40.5
W
°C/W
°C/W
RF
260 peak
°C
Lead Temperature Soldering (10 sec):
Reflow (SMD styles only) Pb−Free (Note 3)
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
1. 1: The maximum package power dissipation limit must not be exceeded.
PD +
T J(max) * T A
R qJA
2. The value of qJA is measured with the device mounted on a 3in x 3in, 4 layer, 0.062 inch FR−4 board with 1.5 oz. copper on the top and
bottom layers and 0.5 ounce copper on the inner layers, in a still air environment with TA = 25°C. The PCB part layout had 12 thermal vias
(see Recommended Land Pattern in applications section of this data sheet
3. 60−180 seconds minimum above 237°C.
4. 10 V transients allowed for , 10 ns.
RECOMMENDED OPERATING CONDITIONS
Rating
Symbol
Min
Input voltage
VI
Operating junction temperature
TJ
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4
Typ
Max
Unit
3
6
V
–40
125
°C
NCP1592
ELECTRICAL CHARACTERISTICS Over operating free−air temperature range unless otherwise noted
Parameter
Symbol
Test Conditions
Min
Typ
MAX
Unit
3
6
V
Power Supply, VIN
VIN Operation Voltage
Quiescent Current
VIN
I(QSW 350)
Fs = 350 kHz, SYNC ≤ 0.8 V, RT
open, PH pin open
3.5
11.2
mA
I(QSW 550)
Fs = 550 kHz, SYNC ≥ 2.5 V, RT
open, PH pin open
4.0
16
mA
I(QSD)
Shutdown, SS / ENA = 0 V
1
1.4
mA
2.95
3.0
V
UNDERVOLTAGE LOCKOUT
Start Threshold
Stop Threshold
UVLO Hysteresis
Rising and falling edge deglitch
(Note 5)
UVLOR
UVLOF
2.7
2.8
V
UVLOHYST
110
160
mV
2.5
ms
UVLORTD
BIAS VOLTAGE
Output Voltage
Vbias
Output Current (Note 6)
IVbias
IVbias = 0
2.7
2.8
2.90
V
100
mA
0.900
V
IL = 3 A, Fs = 350 kHz, TJ = 85°C
0.04
%/V
IL = 3 A, Fs = 550 kHz, TJ = 85°C
0.04
IL = 0 A to 6 A, Fs = 350 kHz,
TJ = 85°C
0.03
IL = 0 A to 6 A, fs = 550 kHz,
TJ = 85°C
0.03
CUMULATIVE REFERENCE
Reference Voltage Accuracy
Vref
0.882
0.891
REGULATION
Line regulation (Notes 6 and 7)
Load regulation (Notes 5 and 7)
%/A
OSCILLATOR
Internally set
Externally set
High level threshold
Low level threshold
External synchronization pulse
duration (Note 5)
Frequency range (Note 5)
Ramp valley (Note 5)
FREQSYNC_LOW
SYNC ≤ 0.8 V, RT open
280
350
420
FREQ_HIGH
SYNC ≥ 2.5 V, RT open
440
550
660
FREQ180RT
RT = 180 kW (1% resistor to
AGND) (Note 5)
252
280
308
FREQ100RT
RT = 100 kW (1% resistor to
AGND)
460
500
540
FREQ68RT
RT = 68 kW (1% resistor to
AGND) (Note 5)
663
700
762
SYNCH
2.5
0.8
50
SYNCFREQ
330
kHz
V
SYNCL
SYNCMIN
kHz
V
ns
700
kHz
RAMP_Bot
0.441
V
Peak−to−peak ramp amplitude
(Note 5)
RAMP_AMP
1
V
Minimum controllable on time
(Note 5)
MIN_COT
Maximum duty cycle
5.
6.
7.
8.
200
DMAX
90%
Guaranteed by design.
Static resistive loads only.
Specified by the circuit used in Figure 14.
Matched MOSFETs low−side RDS(on) production tested, high−side RDS(on) specified by design.
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5
ns
NCP1592
ELECTRICAL CHARACTERISTICS Over operating free−air temperature range unless otherwise noted
Parameter
Symbol
Test Conditions
Min
Typ
MAX
Unit
OLG
1 kW COMP to AGND (Note 5)
90
110
dB
Unity gain bandwidth
UGBW
Parallel 10 kW, 160 pF COMP to
AGND (Note 5)
3
5
MHz
Common mode input voltage
range
CMIVR
Powered by internal LDO
(Note 5)
0
IVSENSE
VSENSE = Vref
ERROR AMPLIFIER
Open loop voltage gain
Input bias current
60
VBIAS
V
250
nA
Output voltage slew rate
(Positives)
EASRP
3.0
4.5
V/ms
Output voltage slew rate
(Negatives)
EASRN
2.07
3.0
V/ms
PWM COMPARATOR
PWM comparator propagation
delay time, PWM comparator
input to PH pin (excluding
deadtime)
COMPDLY
10 mV overdrive (Note 5)
70
85
ns
1.20
1.40
V
SLOW−START/ENABLE
Enable threshold voltage
ENTH
0.82
Enable hysteresis voltage
ENHYS
0.03
V
Falling edge deglitch (Note 5)
EN_DLY
2.5
ms
Internal soft−start time
Charge current
Discharge current
2.18
3.35
4.1
EN_ICH
SSI
SS/ENA = 0 V
3
5
8
ms
mA
EN_IDSCH
SS/ENA = 1.2 V, VI = 2.7 V
2.3
3.1
5.4
mA
POWER GOOD
VSENSE falling
90
%Vref
Power good hysteresis voltage
(Note 5)
3
%Vref
Power good falling edge deglitch
(Note 5)
39
ms
Power good threshold voltage
Output saturation voltage
PWRGD
I(sink) = 2.5 mA
Leakage current
PWRGD
VI = 5.5 V
166
225
mV
3
mA
CURRENT LIMIT
Current limit trip point
VI = 3 V, output shorted (Note 5)
7.2
10
VI = 6 V, Output shorted (Note 5)
10
12
A
Current limit leading edge
blanking time (Note 5)
100
ns
Current limit total response time
(Note 5)
200
ns
THERMAL SHUTDOWN
Thermal shutdown trip point
(Note 5)
135
150
165
°C
Hysteresis (Note 5)
10
OUTPUT POWER MOSFETs
Power MOSFETs RDS(on) High
Side
5.
6.
7.
8.
VI = 6 V (Note 8)
26
47
mW
VI = 3 V (Note 8)
30
61
mW
Guaranteed by design.
Static resistive loads only.
Specified by the circuit used in Figure 14.
Matched MOSFETs low−side RDS(on) production tested, high−side RDS(on) specified by design.
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NCP1592
TYPICAL CHARACTERISTICS
34
32
30
28
26
24
22
20
18
−40 −25 −10
5
20
35
50 65
80
28
26
24
22
20
18
5
20
35
50 65
80
95 110 125
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 5. Drain−Source ON−State Resistance
vs Junction Temperature
Figure 6. Drain−Source ON−State Resistance
vs Junction Temperature
750
800
650
SYNC ≥ 2.5 V
550
450
SYNC ≤ 0.8 V
350
250
−40 −25 −10
5
20
35
50 65
80
RT = 68 kW
700
600
RT = 100 kW
500
400
RT = 180 kW
300
200
−40 −25 −10
95 110 125
5
20
35
50 65
80
95 110 125
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 7. Internally Set Oscillator Frequency
vs Junction Temperature
Figure 8. Externally Set Oscillator Frequency
vs Junction Temperature
895
5
DEVICE POWER LOSSES (W)
Vref−VOLTAGE REFERENCE (mV)
VIN = 5 V
30
16
−40 −25 −10
95 110 125
EXTERNALLY SET OSCILLATOR
FREQUENCY (kHz)
INTERNALLY SET OSCILLATOR FREQUENCY (kHz)
32
VIN = 3.3 V
DRAIN SOURCE ON−STATE
RESISTANCE (mW)
DRAIN SOURCE ON−STATE
RESISTANCE (mW)
36
893
891
889
887
885
−40 −25 −10
5
20
35
50
65
80
95 110 125
TJ = 125°C
FS = 700 kHz
4.5
4
3.5
3
2.5
VI = 3.3 V
2
1.5
VI = 5 V
1
0.5
0
0
1
2
3
4
5
6
7
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 9. Voltage Reference vs Junction
Temperature
Figure 10. Device Power Losses at TJ = 1255C
vs Load Current
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8
NCP1592
TYPICAL CHARACTERISTICS
Vref−VOLTAGE REFERENCE (V)
895
TA = 85°C
IO = 3 A
893
FS = 550 kHz
891
889
887
885
3
3.5
4
4.5
5
5.5
6
VI, NPUT VOLTAGE (V)
140
160
120
140
100
120
GAIN (dB)
80
100
Phase
60
80
40
60
Gain
20
40
0
RL = 10 kW
CL = 160 pF
TA = 25°C
−20
−40
1
10
100
20
0
−20
10M 100M
1k
10k
100k 1M
F, FREQUENCY (Hz)
Figure 12. Error Amplifier Open Loop
Response
INTERNAL SLOW−START TIME (ms)
3.9
3.8
3.7
3.6
3.5
3.4
−40 −25 −10
5
20
35
50
65
80
95 110 125
TJ, JUNCTION TEMPERATURE (°C)
Figure 13. Internal Slow−Start Time vs
Junction Temperature
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PHASE MARGIN (°)
Figure 11. Output Voltage Regulation vs. Input
Voltage
NCP1592
APPLICATION INFORMATION
exposed thermal PowerPAD underneath the integrated
circuit package must be soldered to the printed−circuit
board.
Figure 14 shows the schematic diagram for a typical
NCP1592 application. The NCP1592 (U1) can provide
greater than 6 A of output current at a nominal output
voltage of 3.3 V. For proper thermal performance, the
VI
C2
+
C8
10 mF
U1
NCP1592
200 mF
10 V
28
R2
10 kW
VIN
RT
VIN
27
SYNC
VIN
26
VIN
SS/ENA
C1
0.047 mF
VIN
25
PH
VBIAS
C4
0.1 mF PWRGD
PH
4
PH
PWRGD
3
PH
PH
COMP
PH
PH
PH
2
PH
VSENSE
BOOT
PGND
C5
C3
PGND
1
6.8 nF
PGND
AGND
PGND
68 pF
PGND
24
23
22
21
L1
4.7μH
20
14
+ C9
13
+
C10
Vo
C 11
100 pF
12
470 mF
470 mF
11
4V
4V
10
9
8
7
6
5
19
18
C7
0.047 mF
17
16
15
POWERPAD
R1
9.76 kW
R2
3.74 kW
R5
1.18 kW
C6
12 nF
R4
10 kW
Figure 14. Application Circuit
COMPONENT SELECTION
FEEDBACK CIRCUIT
The resistor divider network of R3 and R4 sets the output
voltage for the circuit at 3.3 V. R4, along with R1, R5, C3,
C5, and C6 form the loop compensation network for the
circuit. For this design, a Type 3 topology is used.
INPUT FILTER
The input to the circuit is a nominal 5 VDC. The input
filter C2 is a 220 μF POSCAP capacitor, with a maximum
allowable ripple current of 3 A. C8 provides high frequency
decoupling of the NCP1592 from the input supply and must
be located as close as possible to the device. Ripple current
is carried in both C2 and C8, and the return path to PGND
must avoid the current circulating in the output capacitors
C9 and C10.
OPERATING FREQUENCY
In the application circuit, the 350 kHz operation is
selected by leaving RT and SYNC open. Connecting a
180 kW to 68 kW resistor between RT (pin 28) and analog
ground can be used to set the switching frequency to
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NCP1592
Use vias to connect this ground area to any internal ground
planes. Additional vias are also used at the ground side of the
input and output filter capacitors. The AGND and PGND
pins are tied to the PCB ground by connecting them to the
ground area under the device as shown. The only
components that tie directly to the power ground plane are
the input capacitors, the output capacitors, the input voltage
decoupling capacitor, and the PGND pins of the NCP1592.
Use a separate wide trace for the analog ground signal path.
The analog ground is used for the voltage set point divider,
timing resistor RT, slow−start capacitor and bias capacitor
grounds. Connect this trace directly to AGND (Pin 1).
The PH pins are tied together and routed to the output
inductor. Since the PH connection is the switching node, the
inductor is located close to the PH pins. The area of the PCB
conductor is minimized to prevent excessive capacitive
coupling. Connect the boot capacitor between the phase
node and the BOOT pin as shown. Keep the boot capacitor
close to the IC and minimize the conductor trace lengths.
Connect the output filter capacitor(s) as shown between
the VOUT trace and PGND. It is important to keep the loop
formed by the PH pins, LOUT, COUT and PGND as small
as practical.
Place the compensation components from the VOUT
trace to the VSENSE and COMP pins. Do not place these
components too close to the PH trace. Due to the size of the
IC package and the device pin−out, they must be routed
close, but maintain as much separation as possible while still
keeping the layout compact.
Connect the bias capacitor from the VBIAS pin to analog
ground using the isolated analog ground trace. If a
slow−start capacitor or RT resistor is used, or if the SYNC
pin is used to select 350 kHz operating frequency, connect
them to this trace.
280 kHz to 700 kHz. To calculate the RT resistor, use the
equation below:
R+
500 kHz
Switching Frequency
100 [kW]
(eq. 1)
OUTPUT FILTER
The output filter is composed of a 4.7 μH inductor and two
470 μF capacitors. The inductor is a low dc resistance
(12 mW) type, Coiltronics UP3B−4R7. The capacitors used
are 4 V POSCAP types with a maximum ESR of 0.040 W.
The feedback loop is compensated so that the unity gain
frequency is approximately 25 kHz.
PCB LAYOUT
Figure 15 shows a generalized PCB layout guide for
NCP1592.
The VIN pins are connected together on the
printed−circuit board (PCB) and bypassed with a low−ESR
ceramic−bypass capacitor. Care should be taken to minimize
the loop area formed by the bypass capacitor connections,
the VIN pins, and the NCP1592 ground pins. The minimum
recommended bypass capacitance is 10 mF ceramic
capacitor with a X5R or X7R dielectric and the optimum
placement is closest to the VIN pins and the PGND pins.
The NCP1592 has two internal grounds (analog and
power). Inside the NCP1592, the analog ground ties to all of
the noise sensitive signals, while the power ground ties to the
noisier power signals. Noise injected between the two
grounds can degrade the performance of the NCP1592,
particularly at higher output currents. However, ground
noise on an analog ground plane can also cause problems
with some of the control and bias signals. Therefore,
separate analog and power ground traces are recommended.
There is an area of ground on the top layer directly under the
IC, with an exposed area for connection to the PowerPAD.
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NCP1592
Figure 15. Recommended Land Pattern For 28−Pin PowerPAD
LAYOUT CONSIDERATIONS FOR THERMAL
PERFORMANCE
desired. Connection from the exposed area of the
PowerPAD to the analog ground
plane layer must be made using 0.013 inch diameter vias
to avoid solder wicking through the vias. Eight vias must be
in the PowerPAD area with four additional vias located
under the device package. The size of the vias under the
package, but not in the exposed thermal pad area, can be
increased to 0.018. Additional vias beyond the twelve
recommended that enhance thermal performance must be
included in areas not under the device package.
For operation at full rated load current, the analog ground
plane must provide an adequate heat dissipating area. A
3−inch by 3−inch plane of 1 copper is recommended, though
not mandatory, depending on ambient temperature and
airflow. Most applications have larger areas of internal
ground plane available, and the PowerPAD must be
connected to the largest area available. Additional areas on
the top or bottom layers also help dissipate heat, and any area
available must be used when 6 A or greater operation is
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NCP1592
Minimum recommended Thermal Vias: 8x
0.013 Diameter Inside PowerPAD area 4 x
0.018 Diameter Under Device as Shown.
Additional 0.018 Diameter Vias May Be Used
if Top Side Analog Ground Area is Extended.
Connect Pin 1 to Analog Ground
q0.0130
Plane in this Area for Optimum Performance
q0.0180
0.0600
0.0150
0.0339
0.0650
0.0256
0.0500
0.2090
0.0500
0.3820
0.3478
0.0500
0.0650
0.0339
Minimum Recommended Exposed
Minimum recommended Top
Side Analog Ground Area
0.1700
Copper Area for PowerPAD, 5 mm
0.1340
Stencils May Require 10%
Larger Area
0.0630
0.0400
Figure 16. Recommended Land Pattern For 28−Pin PowerPAD
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NCP1592
PERFORMANCE GRAPHS
100
100
VO = 3.3 V
VO = 2.5 V
90
VO = 1.8 V
80
EFFICIENCY (%)
EFFICIENCY (%)
90
VO = 1.2 V
70
VI = 3.3 V
f = 550 kHz
L = 4.7 mH
TA = 25°C
60
50
0
1
2
3
4
5
VO = 1.2 V
70
VI = 5 V
f = 550 kHz
L = 4.7 mH
TA = 25°C
60
50
7
6
VO = 1.8 V
80
IO, OUTPUT CURRENT (A)
0
1
2
3
4
5
IO, OUTPUT CURRENT (A)
Figure 17. Efficiency vs Output Current
Figure 18. Efficiency vs Output Current
1.004
VI = 5 V
VO = 3.3 V
TA = 25°C
Fs = 550 kHz
LOAD REGULATION
1.003
1.002
1.001
1
0.999
0.998
0.997
0.996
0
1
2
3
4
5
6
IO, OUTPUT CURRENT (A)
Figure 20. Loop Response
Figure 19. Load Regulation vs Input Voltage
AMBIENT TEMPERATURE (°C)
125
115
VI = 5.0 V
105
95
TA = 125°C
Fs = 700 kHz
VI = 3.3 V
85
75
65
55
45
35
25
0
1
2
3
4
5
6
6
7
8
Figure 22. Output Ripple Voltage
IL, LOAD CURRENT (A)
Figure 21. Ambient Temperature vs Load
Current
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7
NCP1592
PERFORMANCE GRAPHS
1.002
IOUT, OUTPUT CURRENT
1.0015
1.001
0A
3A
6A
1.0005
1
0.9995
0.999
0.9985
0.998
4
4.5
5
5.5
VI, INPUT VOLTAGE (V)
6
Figure 23. Line Regulation vs Output Current
Figure 24. Load Transient Response
Figure 25. Slow Start Timing
Figure 26 shows the schematic diagram for a reduced size,
high frequency application using the NCP1592. The
NCP1592 (U1) can provide up to 6 A of output current at a
nominal output voltage of 1.8 V. A small size 0.56 μH
inductor is used and the switching frequency is set to
680 kHz by R1. The compensation network is optimized for
fast transient response as shown in Figure 27. For good
thermal performance, the PowerPAD underneath the
integrated circuit NCP1592 needs to be soldered well to the
printed−circuit board.
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NCP1592
VI
C1
10 mF
C2
10 mF
C2
10 mF
C1
10 mF
U1
NCP1592
R1
68.1 kW
28
VIN
RT
VIN
27
SYNC
C3
22 nF
VIN
26
VIN
SS/ENA
C4
100 nF
VIN
25
PH
VBIAS
PH
4
PWRGD
C5
1 nF
R2
3.4 kW
PH
3
PH
PH
COMP
PH
C6
150 pF
PH
PH
2
PH
VSENSE
R5
90.9 kW
BOOT
PGND
R3
332 W
R6
10 kW
PGND
1
PGND
AGND
PGND
C12
5.6 nF
PGND
24
23
22
21
20
14
13
12
11
10
9
8
7
L1
1 mH
6
+
5
19
18
470 mF
C7
100 nF
17
15
POWERPAD
Figure 26. Small Size, High Frequency Design
Figure 27. Transient Response, 1.5 to 4.5 A Step
15
R4
10 W
16
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C9
C 11
1000 pF
Vo
C10
10 mF
NCP1592
DETAILED DESCRIPTION
UNDERVOLTAGE LOCK OUT (UVLO)
VBIAS REGULATOR (VBIAS)
The NCP1592 incorporates an under voltage lockout
circuit to keep the device disabled when the input voltage
(VIN) is insufficient. During power up, internal circuits are
held inactive until VIN exceeds the nominal UVLO
threshold voltage of 2.95 V. Once the UVLO start threshold
is reached, device start−up begins. The device operates until
VIN falls below the nominal UVLO stop threshold of 2.8 V.
Hysteresis in the UVLO comparator, and a 2.5 μs rising and
falling edge deglitch circuit reduce the likelihood of shutting
the device down due to noise on VIN.
The VBIAS regulator provides internal analog and digital
blocks with a stable supply voltage over variations in
junction temperature and input voltage.
A high quality, low−ESR, ceramic bypass capacitor is
required on the VBIAS pin. X7R or X5R grade dielectrics
are recommended because their values are more stable over
temperature. The bypass capacitor must be placed close to
the VBIAS pin and returned to AGND.
External loading on VBIAS is allowed, with the caution
that internal circuits require a minimum VBIAS of 2.70 V,
and external loads on VBIAS with ac or digital switching
noise may degrade performance. The VBIAS pin may be
useful as a reference voltage for external circuits.
SLOW−START/ENABLE (SS/ENA)
The slow−start/enable pin provides two functions. First,
the pin acts as an enable (shutdown) control by keeping the
device turned off until the voltage exceeds the start threshold
voltage of approximately 1.2 V. When SS/ENA exceeds the
enable threshold, device start−up begins. The reference
voltage fed to the error amplifier is linearly ramped up from
0 V to 0.891 V in 3.35 ms. Similarly, the converter output
voltage reaches regulation in approximately 3.35 ms.
Voltage hysteresis and a 2.5−μs falling edge deglitch
circuit reduce the likelihood of triggering the enable
due to noise.
The second function of the SS/ENA pin provides an
external means of extending the slow−start time with a
low−value capacitor connected between SS/ENA and
AGND.
Adding a capacitor to the SS/ENA pin has two effects on
start−up. First, a delay occurs between release of the
SS/ENA pin and start−up of the output. The delay is
proportional to the slow−start capacitor value and lasts until
the SS/ENA pin reaches the enable threshold. The start−up
delay is approximately:
t d + C (SS)
1.2 V
5 mA
VOLTAGE REFERENCE
The voltage reference system produces a precise Vref
signal by scaling the output of a temperature stable bandgap
circuit. During manufacture, the bandgap and scaling
circuits are trimmed to produce 0.891 V at the output of the
error amplifier, with the amplifier connected as a voltage
follower. The trim procedure adds to the high precision
regulation of the NCP1592, since it cancels offset errors in
the scale and error amplifier circuits.
0SCILLATOR AND PWM RAMP
The oscillator frequency can be set to internally fixed
values of 350 kHz or 550 kHz using the SYNC pin as a static
digital input. If a different frequency of operation is required
for the application, the oscillator frequency can be
externally adjusted from 280 to 700 kHz by connecting a
resistor between the RT pin and AGND and floating the
SYNC pin. The switching frequency is approximated by the
following equation, where R is the resistance from RT to
AGND:
(eq. 2)
Switching Frequency +
Second, as the output becomes active, a brief ramp−up at
the internal slow−start rate may be observed before the
externally set slow−start rate takes control and the output
rises at a rate proportional to the slow−start capacitor. The
slow−start time set by the capacitor is approximately:
t (SS) + C (SS)
0.7 V
5 mA
100 kW
R
500 [kHz] (eq. 4)
External synchronization of the PWM ramp is possible
over the frequency range of 330 kHz to 700 kHz by driving
a synchronization signal into SYNC and connecting a
resistor from RT to AGND. Choose a resistor between the
RT and AGND which sets the free running frequency to 80%
of the synchronization signal. The following table
summarizes the frequency selection configurations:
(eq. 3)
The actual slow−start time is likely to be less than the
above approximation due to the brief ramp−up at the internal
rate.
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NCP1592
Switching Frequency
Sync Pin
RT Pin
350 kHz, internally set
Float or AGND
Float
550 kHz, internally set
≥2.5 V
Float
Externally set 280 kHz to 700 kHz
Float
R= 180 kW to 68 kW
Externally synchronized frequency
Synchronization signal
R = RT value for 80% of external
synchronization frequency
ERROR AMPLIFIER
repeated each cycle in which the current limit comparator is
tripped.
The high performance, wide bandwidth, voltage error
amplifier sets the NCP1592 apart from most dc/dc
converters. The user is given the flexibility to use a wide
range of output L and C filter components to suit the
particular application needs. Type 2 or type 3 compensation
can be employed using external compensation components.
DEAD−TIME CONTROL AND MOSFET DRIVERS
Adaptive dead−time control prevents shoot−through
current from flowing in both N−channel power MOSFETs
during the switching transitions by actively controlling the
turn−on times of the MOSFET drivers. The high−side driver
does not turn on until the voltage at the gate of the low−side
FET is below 2 V. While the low−side driver does not turn
on until the voltage at the gate of the high−side MOSFET is
below 2 V.
The high−side and low−side drivers are designed with
300 mA source and sink capability to quickly drive the
power MOSFETs gates. The low−side driver is supplied
from VIN, while the high−side driver is supplied from the
BOOT pin. A bootstrap circuit uses an external BOOT
capacitor and an internal 2.5 W bootstrap switch connected
between the VIN and BOOT pins. The integrated bootstrap
switch improves drive efficiency and reduces external
component count.
PWM CONTROL
Signals from the error amplifier output, oscillator, and
current limit circuit are processed by the PWM control logic.
Referring to the internal block diagram, the control logic
includes the PWM comparator, OR gate, PWM latch, and
portions of the adaptive dead−time and control logic block.
During steady−state operation below the current limit
threshold, the PWM comparator output and oscillator pulse
train alternately reset and set the PWM latch. Once the PWM
latch is reset, the low−side FET remains on for a minimum
duration set by the oscillator pulse width. During this period,
the PWM ramp discharges rapidly to its valley voltage.
When the ramp begins to charge back up, the low−side FET
turns off and high−side FET turns on. As the PWM ramp
voltage exceeds the error amplifier output voltage, the PWM
comparator resets the latch, thus turning off the high−side
FET and turning on the low−side FET. The low−side FET
remains on until next oscillator pulse discharges the PWM
ramp.
During transient conditions, the error amplifier output
could be below the PWM ramp valley voltage or above the
PWM peak voltage. If the error amplifier is high, the PWM
latch is never reset, and the high−side FET remains on until
the oscillator pulse signals the control logic to turn the
high−side FET off and the low−side FET on. The device
operates at its maximum duty cycle until the output voltage
rises to the regulation set−point, setting VSENSE to
approximately the same voltage as VREF. If the error
amplifier output is low, the PWM latch is continually reset
and the high−side FET does not turn on. The low−side FET
remains on until the VSENSE voltage decreases to a range
that allows the PWM comparator to change states. The
NCP1592 is capable of sinking current continuously until
the output reaches the regulation set−point.
If the current limit comparator trips for longer than 100 ns,
the PWM latch resets before the PWM ramp exceeds the
error amplifier output. The high−side FET turns off and
low−side FET turns on to decrease the energy in the output
inductor and consequently output current. This process is
OVERCURRENT PROTECTION
The cycle−by−cycle current limiting is achieved by
sensing the current flowing through the high−side MOSFET
and comparing this signal to a preset overcurrent threshold.
The high side MOSFET is turned off within 200 ns of
reaching the current limit threshold. A 100 ns leading edge
blanking circuit prevents current limit false tripping.
Current limit detection occurs only when current flows from
VIN to PH when sourcing current to the output filter. Load
protection during current sink operation is provided by
thermal shutdown.
THERMAL SHUTDOWN
The device uses the thermal shutdown to turn off the
power MOSFETs and disable the controller if the junction
temperature exceeds 150°C. The device is released from
shutdown automatically when the junction temperature
decreases to 10°C below the low thermal shutdown trip
point, and starts up under control of the slow−start circuit.
Thermal shutdown provides protection when an overload
condition is sustained for several milliseconds. With a
persistent fault condition, the device cycles continuously;
starting up by control of the soft−start circuit, heating up due
to the fault condition, and then shutting down upon reaching
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NCP1592
the UVLO threshold or SS/ENA is low, or a thermal
shutdown occurs. When VIN ≥ UVLO threshold, SS/ENA
≥ enable threshold, and VSENSE > 90% of Vref, the open
drain output of the PWRGD pin is high. A hysteresis voltage
equal to 3% of Vref and a 35 μs falling edge deglitch circuit
prevent tripping of the power good comparator due to high
frequency noise.
the thermal shutdown trip point. This sequence repeats until
the fault condition is removed.
POWER−GOOD (PWRGD)
The power good circuit monitors for under voltage
conditions on VSENSE. If the voltage on VSENSE is 10%
below the reference voltage, the open−drain PWRGD output
is pulled low. PWRGD is also pulled low if VIN is less than
ORDERING INFORMATION
Device
NCP1592PAR2G
Temperature
Range (5C)
−40 to +125
Package
Shipping†
TSSOP−28 EP
(Pb−Free)
2500 / Tape & Reel
†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging
Specifications Brochure, BRD8011/D.
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NCP1592
PACKAGE DIMENSIONS
TSSOP28 9.7x4.4 EP
CASE 948BG
ISSUE O
NOTE 6
B
28
E1
NOTE 5
PIN ONE
LOCATION
b
15
c1
ÇÇÇÇ
ÇÇÇÇ
E
1
2X 14 TIPS
TOP VIEW
0.05 C
A2
NOTE 4
DETAIL A
B
0.10 C
28X
b
0.10 C B A
C
SEATING
PLANE
NOTE 3
SIDE VIEW
M
c
A
28X
NOTE 8
0.20 C B A
NOTE 6
D
SECTION B−B
c
14
A
e
ÉÉÉ
ÇÇÇ
ÇÇÇ
ÉÉÉ
b1
B
END VIEW
NOTES:
1. DIMENSIONS AND TOLERANCING PER
ASME Y14.5M, 1994.
2. DIMENSIONS IN MILLIMETERS.
3. DIMENSION b DOES NOT INCLUDE DAMBAR
PROTRUSION. DAMBAR PROTRUSION
SHALL BE 0.07 MAX AT MAXIMUM MATERIAL
CONDITION. DAMBAR CANNOT BE LOCATED
ON THE LOWER RADIUS OF THE FOOT. MINIMUM SPACE BETWEEN PROTRUSION AND
ADJACENT LEAD IS 0.07.
4. DIMENSION D DOES NOT INCLUDE MOLD
FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE
BURRS SHALL NOT EXCEED 0.15 PER SIDE.
DIMENSION D IS DETERMINED AT DATUM
PLANE H.
5. DIMENSION E1 DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT
EXCEED 0.25 PER SIDE. DIMENSION E1 IS
DETERMINED AT DATUM PLANE H.
6. DATUMS A AND B TO BE DETERMINED AT
DATUM PLANE H.
7. A1 IS DEFINED AS THE VERTICAL DISTANCE
FROM THE SEATING PLANE TO THE LOWEST POINT ON THE PACKAGE BODY.
8. SECTION B−B TO BE DETERMINED AT 0.10
TO 0.25 FROM THE LEAD TIP.
D2
H
L2
E2
A1
L
NOTE 7
C
GAUGE
PLANE
DETAIL A
BOTTOM VIEW
RECOMMENDED
SOLDERING FOOTPRINT*
28X
6.47
1.15
2.70
6.70
1
28X
0.65
PITCH
0.30
DIMENSIONS: MILLIMETERS
*For additional information on our Pb−Free strategy and soldering
details, please download the ON Semiconductor Soldering and
Mounting Techniques Reference Manual, SOLDERRM/D.
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DIM
A
A1
A2
b
b1
c
c1
D
D2
E
E1
E2
e
L
L2
M
MILLIMETERS
MIN
MAX
−−−
1.20
0.00
0.15
0.80
1.05
0.19
0.30
0.19
0.25
0.09
0.20
0.09
0.16
9.60
9.80
5.21
6.17
6.40 BSC
4.30
4.50
1.44
2.40
0.65 BSC
0.45
0.75
0.25 BSC
0_
8_
NCP1592
ON Semiconductor and
are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC owns the rights to a number of patents, trademarks,
copyrights, trade secrets, and other intellectual property. A listing of SCILLC’s product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent−Marking.pdf. SCILLC
reserves the right to make changes without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any
particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without
limitation special, consequential or incidental damages. “Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications
and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC
does not convey any license under its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for
surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where
personal injury or death may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and
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any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture
of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
PUBLICATION ORDERING INFORMATION
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Phone: 303−675−2175 or 800−344−3860 Toll Free USA/Canada
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For additional information, please contact your local
Sales Representative
NCP1592/D