ON NCP1530DM27R2 600 ma pwm/pfm step-down converter with external synchronization pin Datasheet

NCP1530
600 mA PWM/PFM
Step−Down Converter with
External Synchronization Pin
The NCP1530 is a PWM/PFM non−synchronous step−down
(Buck) DC−DC converter for usage in systems supplied from 1−cell
Li−ion, or 2 or more cells Alkaline/NiCd/NiMH batteries. It can
operate in Constant−Frequency PWM mode or PWM/PFM mode in
which the controller will automatically switch to PFM mode
operation at low output loads to maintain high efficiency. The
switching frequency can also be synchronized to external clock
between 600 kHz and 1.2 MHz. The maximum output current is up
to 600 mA. Applying an external synchronizing signal to SYN pin
can supersede the PFM operation.
The NCP1530 consumes only 47 A (typ) of supply current
(VOUT = 3.0 V, no switching) and can be forced to shutdown mode by
bringing the enable input (EN) low. In shutdown mode, the regulator
is disabled and the shutdown supply current is reduced to
0.5 A (typ). Other features include built−in undervoltage lockout,
internal thermal shutdown, an externally programmable soft−start
time and output current limit protection. The NCP1530 operates
from a maximum input voltage of 5.0 V and is available in a space
saving, low profile Micro8 package.
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MARKING
DIAGRAM
Micro8
DM SUFFIX
CASE 846A
8
1
xxxx
A
L
Y
W
• Pb−Free Package is Available
• High Conversion Efficiency, up to 92% at VIN = 4.3 V,
•
•
•
•
•
•
•
•
•
= Specific Device Code
= Assembly Location
= Wafer Lot
= Year
= Work Week
PIN CONNECTIONS
Features
•
•
•
xxxx
ALYW
VOUT = 3.3 V, IOUT = 300 mA
Current−Mode PWM Control
Automatic PWM/PFM Mode for Current Saving at Low Output Loads
Internal Switching Transistor Support 600 mA Output Current
(VIN = 5.0 V, VOUT = 3.3 V)
High Switching Frequency (600 kHz), Support Small Size Inductor
and Capacitor, Ceramic Capacitors Can be Used
Synchronize to External Clock Signal up to 1.2 MHz
100% Duty Cycle for Maximum Utilization of the Supply Source
Programmable Soft−Start Time through External Chip Capacitor
Externally Accessible Voltage Reference
Built−In Input Undervoltage Lockout
Built−In Output Overvoltage Protection
Power Saving Shutdown Mode
Space Saving, Low Profile Micro8 Package
VIN
1
8
LX
SYN
2
7
VREF
SS
3
6
VOUT
GND
4
5
EN
(Top View)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 14 of this data sheet.
Typical Applications
•
•
•
•
•
•
PDAs
Digital Still Camera
Cellular Phone and Radios
Portable Test Equipment
Portable Scanners
Portable Audio Systems
 Semiconductor Components Industries, LLC, 2004
November, 2004 − Rev. 3
1
Publication Order Number:
NCP1530/D
NCP1530
L1 5.6 H
VIN = 2.8 V to 5.0 V
VIN
VOUT = 3.0 V
LX
D1
MBRM120ET3
NCP1530
SYN
SS
VOUT
VREF
*CSS
EN
GND
CIN
22 F
*CVREF
1.0 F
COUT
22 F
*Optional Component
Figure 1. Typical Step−Down Converter Application
VIN 1
EN 5
ENABLE
DETECT
THERMAL
SHUTDOWN
MASTER ENABLE
UVLO
ISEN
SYN 2
MODE
SELECTION
SYNC
DETECT
AND
TIMING
BLOCK
ISEN
MODE
ISEN
ILIMIT
ISEN
−
+
DRV
−
OV
+
8 LX
0.04
VREF
CONTROL
LOGIC
−
FB
50 nA
−
OTA
+
+
6 VOUT
−
SS 3
VOLTAGE
REFERENCE
AND
SOFT−START
+
VREF
FB
10 pF
VREF 7
4 GND
Figure 2. Simplified Functional Block Diagram
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2
NCP1530
PIN FUNCTION DESCRIPTIONS
Pin
Symbol
Description
1
VIN
Unregulated Supply Input.
2
SYN
Oscillator Synchronization and Mode Selection Input.
SYNC = GND (Automatic PWM/PFM mode) The converter operates at 600 kHz fixed−frequency PWM mode
primarily, and automatically switches to variable−frequency PFM mode at small output loads for power saving.
SYNC = VIN (Constant−Frequency PWM mode) The converter operates at 600 kHz fixed−frequency PWM mode
always.
SYNC = External clock signal between 600 to 1200 kHz. The converter will be synchronized with the external
clock signal.
The SYNC pin is internally pulled to GND.
3
SS
Soft−Start Timing control pin. An external soft−start capacitor can be connected to this pin if extended soft−start is
required. A 50 nA current will be sourced from this pin to charge up the capacitor during startup and gently ramps
the device into service to prevent output voltage overshoot. If this pin is floated, built−in 500 s (typ.) soft−start
will be activated.
4
GND
5
EN
6
VOUT
Feedback Terminal. The output voltage is sensed by this pin.
7
VREF
Connected to voltage reference decoupling capacitor. For noise non−sensitive applications, the internal voltage
reference can operate without decoupling capacitor.
8
LX
Ground Terminal.
Active−High Enable Input. Active to enable the device. Bring this pin to GND and the quiescent current is reduced
to less than 0.5 A. This pin is internally pulled to VIN.
Inductor Terminal. This pin is connected to the drains of the internal P−channel switching transistors. The inductor
must be connected between this pin and the output terminal.
MAXIMUM RATINGS
Rating
Symbol
Value
Unit
Power Supply (Pin 1)
VIN
−0.3 to 6
V
Input/Output Pins (Pins 2−4 & Pins 7−8)
VIO
−0.3 to 6
V
Thermal Characteristics
Micro8 Plastic Package
Thermal Resistance, Junction−to−Air
RJA
240
°C/W
TJ
0 to +150
°C
Operating Junction Temperature Range
Operating Ambient Temperature Range
TA
0 to +85
°C
Storage Temperature Range
Tstg
−55 to +150
°C
Maximum ratings are those values beyond which device damage can occur. Maximum ratings applied to the device are individual stress limit values
(not normal operating conditions) and are not valid simultaneously. If these limits are exceeded, device functional operation is not implied, damage
may occur and reliability may be affected.
1. This device series contains ESD protection and exceeds the following tests:
Human Body Model (HBM) 2.0 kV per JEDEC standard: JESD22−A114.
Machine Model (MM) 200 V per JEDEC standard: JESD22−A115.
2. Latchup Current Maximum Rating: 150 mA per JEDEC standard: JESD78.
3. Moisture Sensitivity Level (MSL): 1 per IPC/JEDEC standard: J−STD−020A.
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3
NCP1530
ELECTRICAL CHARACTERISTICS (VIN = VR + 1.0 V, test circuit, refer to Figure 1, CSS = NC and CVREF = 1.0 F, TA = 25°C for
typical value, 0°C ≤ TA ≤ 85°C for min/max values unless otherwise noted.) *VR is the factory−programmed output voltage setting.
Characteristic
Symbol
Min
Typ
Max
Unit
VIN
1.1 VR
−
5.0
V
2.425
2.619
2.910
3.201
2.5
2.7
3.0
3.3
2.575
2.781
3.090
3.399
IOUT(max)
600
−
−
mA
IIN
−
45
95
A
ISHDN
−
0.5
1.0
A
ILX
−
−
1.0
A
RDS(ON)
−
0.3
0.5
fOSC
480
600
720
kHz
Maximum PWM Duty Cycle (Note 5)
DMAX−PWM
−
−
100
%
PFM to PWM Switch−Over Current Threshold
(VIN = 4.5 V, SYN Pin NC, L = 5.6 H, COUT = 22 F) (Note 5)
NCP1530DM25R2
NCP1530DM27R2
NCP1530DM30R2
NCP1530DM33R2
IPFM−PWM
PWM to PFM Switch−Over Current Threshold
(VIN = 4.5 V, SYN Pin NC, L = 5.6 H, COUT = 22 F) (Note 5)
NCP1530DM25R2
NCP1530DM27R2
NCP1530DM30R2
NCP1530DM33R2
IPWM−PFM
Input Voltage
Output Voltage (Iload = 150 mA, VR + 1.0 V < VIN < 5.0 V) (Note 4)
NCP1530DM25R2
NCP1530DM27R2
NCP1530DM30R2
NCP1530DM33R2
VOUT
Maximum Output Current (VIN = 5.0 V, VOUT = 3.0 V) (Note 5)
Supply Current (VIN = VR + 1.0 V, No Load, EN and SYN Pins NC)
Shutdown Supply Current (VIN = 5.0 V, No Load, VEN = 0 V)
LX Pin Leakage Current (No Load, VEN = 0 V)
Internal P−FET ON Resistance at LX Pin
(VIN = VR + 1.0 V, ILoad = 150 mA)
Oscillator Frequency
(VIN = VEN = VR + 1.0 V, ILoad = 100 mA, SYN Pin NC)
V
mA
−
−
−
−
83
90
100
102
−
−
−
−
mA
−
−
−
−
27
38
39
48
−
−
−
−
VUVLO
−
2.0
2.45
V
VREF
1.184
1.20
1.216
V
Reference Voltage Temperature Coefficient
(VIN = VR + 1.0 V, CVREF = 1.0 F) (Note 5)
TCVREF
−
0.03
−
mV/°C
Reference Voltage Load Current
(VIN = VR + 1.0 V, CVREF = 1.0 F) (Note 6)
IVREF
5.0
−
−
mA
Enable Logic High Threshold Voltage (VIN = VR + 1.0 V, ILoad = 0 mA)
VEN−H
−
1.5
1.85
V
Input Undervoltage Lockout Threshold
Reference Voltage (VIN = VR + 1.0 V, CVREF = 1.0 F)
Enable Logic Low Threshold Voltage (VIN = VR + 1.0 V, ILoad = 0 mA)
VEN−L
0.5
1.2
−
V
tPWM−ON
−
100
−
ns
%VOV
−
6.0
12
%
PWM Cycle−by−Cycle Current Limit (Note 5)
ILIM
−
1.5
−
A
Built−in Soft−Start Time (VOUT = 3.0 V, SS Pin NC) (Note 5)
tSS
−
500
−
s
Thermal Shutdown Threshold (VIN = 3.5 V, ILoad = 0 mA) (Note 5)
THSHD
−
145
−
°C
Thermal Shutdown Hysteresis (VIN = 3.5 V, ILoad = 0 mA) (Note 5)
THHSYS
−
15
−
°C
PWM Minimum On−Time (Note 5)
PWM OV Protection Level
4. Tested at VIN = VR + 1.0 V in production only. Full VIN range guaranteed by design.
5. Parameter guaranteed by design only, not tested in production.
6. Loading capability decreases with VOUT decreases.
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NCP1530
TYPICAL OPERATING CHARACTERISTICS (VIN = VR + 1.0 V, test circuit, refer to Figure 1, CSS = NC and CVREF = 1.0 F, TA =
25°C for typical value, 0°C ≤ TA ≤ 85°C for min/max values unless otherwise noted.) *VR is the factory−programmed output voltage setting.
2.60
2.80
ILoad = 150 mA
VOUT, OUTPUT VOLTAGE (V)
VOUT, OUTPUT VOLTAGE (V)
ILoad = 150 mA
2.55
VIN = 3.5 V
2.50
VIN = 5.0 V
2.45
2.40
0
17
34
51
68
2.75
VIN = 3.7 V
2.70
2.60
85
VIN = 5.0 V
2.65
0
TA, AMBIENT TEMPERATURE (°C)
ILoad = 150 mA
VOUT, OUTPUT VOLTAGE (V)
VOUT, OUTPUT VOLTAGE (V)
68
85
3.40
3.05
VIN = 4.0 V
3.00
VIN = 5.0 V
2.95
0
17
34
51
68
ILoad = 150 mA
3.35
VIN = 4.3 V
3.30
VIN = 5.0 V
3.25
3.20
85
0
TA, AMBIENT TEMPERATURE (°C)
17
34
51
68
85
TA, AMBIENT TEMPERATURE (°C)
Figure 6. Output Voltage vs. Ambient Temperature
(VOUT = 3.3 V)
Figure 5. Output Voltage vs. Ambient Temperature
(VOUT = 3.0 V)
90
500
ISHDN, SHUTDOWN CURRENT (nA)
IIN, SUPPLY CURRENT (A)
51
Figure 4. Output Voltage vs. Ambient Temperature
(VOUT = 2.7 V)
3.10
VIN = VR + 1.0 V
ILoad = 0 mA
75
60
3.0
3.0VV
3.3 V
45
2.5 V
30
34
TA, AMBIENT TEMPERATURE (°C)
Figure 3. Output Voltage vs. Ambient Temperature
(VOUT = 2.5 V)
2.90
17
0
17
34
2.7 V
51
68
400
300
3.3 V
200
100
0
85
VIN = 5.0 V
ILoad = 0 mA
2.5 V
0
TA, AMBIENT TEMPERATURE (°C)
17
34
51
68
85
TA, AMBIENT TEMPERATURE (°C)
Figure 7. Supply Current vs. Ambient Temperature
Figure 8. Shutdown Current vs. Ambient Temperature
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5
750
RDS(ON), P−FET ON RESISTANCE ()
0.50
VIN = VREN=VR + 1.0 V
ILoad = 0 mA
SYN Pin = NC
675
3.0 V
3.3 V
600
2.5 V
2.7 V
525
450
0
17
34
51
68
85
2.7 V
3.0 V
0.30
0.20
0.10
0
17
PWM
80
60
40
PFM
20
3.5
68
4.0
4.5
5.0
100
PWM
80
60
40
PFM
20
0
3.5
ILOAD, OUTPUT LOADING CURRENT (mA)
PWM
80
60
40
PFM
20
4.5
4.5
5.0
Figure 12. PWM/PFM Switchover Current
Thresholds vs. Input Voltage (VOUT = 2.7 V)
L = 5.6 H, COUT = 22 F
SYN Pin = NC
4.25
4.0
VIN, INPUT VOLTAGE (V)
140
100
85
L = 5.6 H, COUT = 22 F
SYN Pin = NC
120
Figure 11. PWM/PFM Switchover Current
Thresholds vs. Input Voltage (VOUT = 2.5 V)
ILOAD, OUTPUT LOADING CURRENT (mA)
51
140
VIN, INPUT VOLTAGE (V)
0
4.0
34
Figure 10. P−FET ON Resistance
vs. Ambient Temperature
L = 5.6 H, COUT = 22 F
SYN Pin = NC
120
3.3 V
2.5 V
Figure 9. Oscillator Frequency
vs. Ambient Temperature
100
0
0.40
TA, AMBIENT TEMPERATURE (°C)
140
120
VIN = VREN=VR + 1.0 V
ILoad = 0 mA
SYN Pin = NC
TA, AMBIENT TEMPERATURE (°C)
ILOAD, OUTPUT LOADING CURRENT (mA)
ILOAD, OUTPUT LOADING CURRENT (mA)
fOSC, OSCILLATOR FREQUENCY (kHz)
NCP1530
4.75
5.0
140
120
L = 5.6 H, COUT = 22 F
SYN Pin = NC
100
PWM
80
60
40
PFM
20
0
4.25
VIN, INPUT VOLTAGE (V)
4.5
4.75
VIN, INPUT VOLTAGE (V)
Figure 13. PWM/PFM Switchover Current
Thresholds vs. Input Voltage (VOUT = 3.0 V)
Figure 14. PWM/PFM Switchover Current
Thresholds vs. Input Voltage (VOUT = 3.3 V)
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5.0
NCP1530
100
100
PWM/PFM
80
90
SYN 600 kHz
, EFFICIENCY (%)
, EFFICIENCY (%)
90
SYN 1.2 MHz
70
60
PWM
PWM/PFM
80
SYN 600 kHz
SYN 1.2 MHz
70
PWM
60
L = 5.6 H, COUT = 22 F
50
1
10
100
L = 5.6 H, COUT = 22 F
50
1
1000
ILOAD, OUTPUT LOAD CURRENT (mA)
10
100
1000
ILOAD, OUTPUT LOAD CURRENT (mA)
Figure 15. Efficiency vs. Output Load Current
(VIN = 3.5 V, VOUT = 2.5 V)
Figure 16. Efficiency vs. Output Load Current
(VIN = 5.0 V, VOUT = 2.5 V)
100
100
PWM/PFM
90
, EFFICIENCY (%)
, EFFICIENCY (%)
90
80
SYN 1.2 MHz
SYN 600 kHz
70
60
80
70
SYN 1.2 MHz
SYN 600 kHz
L = 5.6 H, COUT = 22 F
10
PWM
60
PWM
50
1
PWM/PFM
100
50
1
1000
ILOAD, OUTPUT LOAD CURRENT (mA)
10
L = 5.6 H, COUT = 22 F
100
1000
ILOAD, OUTPUT LOAD CURRENT (mA)
Figure 17. Efficiency vs. Output Load Current
(VIN = 3.7 V, VOUT = 2.7 V)
Figure 18. Efficiency vs. Output Load Current
(VIN = 5.0 V, VOUT = 2.7 V)
100
100
PWM/PFM
90
, EFFICIENCY (%)
, EFFICIENCY (%)
90
80
SYN 1.2 MHz
SYN 600 kHz
70
60
50
1
80
SYN 600 kHz
10
L = 5.6 H, COUT = 22 F
100
50
1
1000
SYN 1.2 MHz
70
60
PWM
PWM/PFM
ILOAD, OUTPUT LOAD CURRENT (mA)
PWM
L = 5.6 H, COUT = 22 F
10
100
1000
ILOAD, OUTPUT LOAD CURRENT (mA)
Figure 19. Efficiency vs. Output Load Current
(VIN = 4.0 V, VOUT = 3.0 V)
Figure 20. Efficiency vs. Output Load Current
(VIN = 5.0 V, VOUT = 3.0 V)
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NCP1530
100
100
PWM/PFM
PWM/PFM
90
, EFFICIENCY (%)
, EFFICIENCY (%)
90
80
SYN 1.2 MHz
SYN 600 kHz
70
60
SYN 600 kHz
10
100
L = 5.6 H, COUT = 22 F
50
1
1000
ILOAD, OUTPUT LOAD CURRENT (mA)
1000
VIN = 3.5 V
−3.0
5.0
3.0
VIN = 5.0 V
0
VIN = 3.7 V
−3.0
L = 5.6 H, COUT = 22 F
SYNC PIN = NC
10
100
1000
L = 5.6 H, COUT = 22 F
SYNC PIN = NC
−5.0
1
ILOAD, OUTPUT LOAD CURRENT (mA)
10
100
1000
ILOAD, OUTPUT LOAD CURRENT (mA)
Figure 24. Output Voltage Regulation vs.
Output Load Current (VOUT = 2.7 V)
5.0
3.0
VIN =4.0 V
0
VIN = 5.0 V
−3.0
VOUT, OUTPUT VOLTAGE REGULATION (%)
Figure 23. Output Voltage Regulation vs.
Output Load Current (VOUT = 2.5 V)
VOUT, OUTPUT VOLTAGE REGULATION (%)
100
Figure 22. Efficiency vs. Output Load Current
(VIN = 5.0 V, VOUT = 3.3 V)
VOUT, OUTPUT VOLTAGE REGULATION (%)
VOUT, OUTPUT VOLTAGE REGULATION (%)
VIN = 5.0 V
0
5.0
VIN = 5.0 V
3.0
0
VIN = 4.3 V
−3.0
L = 5.6 H, COUT = 22 F
SYNC PIN = NC
−5.0
1
10
ILOAD, OUTPUT LOAD CURRENT (mA)
5.0
−5.0
1
PWM
L = 5.6 H, COUT = 22 F
Figure 21. Efficiency vs. Output Load Current
(VIN = 4.3 V, VOUT = 3.3 V)
3.0
SYN 1.2 MHz
70
60
PWM
50
1
80
10
100
1000
−5.0
1
ILOAD, OUTPUT LOAD CURRENT (mA)
10
100
1000
ILOAD, OUTPUT LOAD CURRENT (mA)
Figure 25. Output Voltage Regulation vs.
Output Load Current (VOUT = 3.0 V)
Figure 26. Output Voltage Regulation vs.
Output Load Current (VOUT = 3.3 V)
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NCP1530
(VIN = 3.5 V, VOUT = 2.5 V, ILOAD = 10 mA)
(VIN = 3.5 V, VOUT = 2.5 V, ILOAD = 80 mA)
Upper Trace: Output Voltage Ripple, 50 mVac/Div.
Lower Trace: LX Pin Switching Waveform, 2.0 V/Div.
Upper Trace: Output Voltage Ripple, 50 mVac/Div.
Lower Trace: LX Pin Switching Waveform, 2.0 V/Div.
Figure 27. PFM Switching Waveform and
Output Ripple for VOUT = 2.5 V
Figure 28. DCM PWM Switching Waveform
and Output Ripple for VOUT = 2.5 V
(VIN = 3.5 V, VOUT = 2.5 V, ILOAD = 600 mA)
(VIN = 4.3 V, VOUT = 3.3 V, ILOAD = 10 mA)
Upper Trace: Output Voltage Ripple, 50 mVac/Div.
Lower Trace: LX Pin Switching Waveform, 2.0 V/Div.
Upper Trace: Output Voltage Ripple, 50 mVac/Div.
Lower Trace: LX Pin Switching Waveform, 2.0 V/Div.
Figure 29. CCM PWM Switching Waveform
and Output Ripple for VOUT = 2.5 V
Figure 30. PFM Switching Waveform and
Output Ripple for VOUT = 3.3 V
(VIN = 4.3 V, VOUT = 3.3 V, ILOAD = 50 mA)
(VIN = 4.3 V, VOUT = 3.3 V, ILOAD = 600 mA)
Upper Trace: Output Voltage Ripple, 50 mVac/Div.
Lower Trace: LX Pin Switching Waveform, 2.0 V/Div.
Upper Trace: Output Voltage Ripple, 50 mVac/Div.
Lower Trace: LX Pin Switching Waveform, 2.0 V/Div.
Figure 31. DCM PWM Switching Waveform
and Output Ripple for VOUT = 3.3 V
Figure 32. CCM PWM Switching Waveform
and Output Ripple for VOUT = 3.3 V
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NCP1530
(VIN = 3.5 V, VOUT = 2.5 V, CSS = 100 pF, No load)
(VIN = 4.3 V, VOUT = 3.3 V, CSS = 100 pF, No load)
Upper Trace: Output Voltage, 2.0 V/Div.
Lower Trace: EN Pin Waveform, 2.0 V/Div.
Time Scale: 5.0 ms/Div.
Upper Trace: Output Voltage, 2.0 V/Div.
Lower Trace: EN Pin Waveform, 2.0 V/Div.
Time Scale: 5.0 ms/Div.
Figure 33. Soft−Start Output Voltage
Waveform for VOUT = 2.5 V
Figure 34. Soft−Start Output Voltage
Waveform for VOUT = 3.3 V
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NCP1530
DETAILED OPERATING DESCRIPTION
Introduction
controlling the ramp up of the internal voltage reference.
The soft−start time can be user adjusted by an external
capacitor, CSS, connecting to the SS pin (pin 3). During
converter powerup, a 50 nA current flowing out from the
SS pin will charge−up the timing capacitor. The voltage
across the SS pin controls the ramp up of the internal
reference voltage by slowly releasing it until the nominal
value is reached. For an external timing capacitor of value
CSS = 100 pF, the soft−start time is about 5.0 ms including
the small logic delay time, Figure 33 and 34. In the case
where the SS pin is left floating, a small built−in capacitor
together with other parasitic capacitance will provide a
minimum intrinsic soft−start time of 500 s. As the
soft−start function is implemented by simple circuitry, the
final timing depends on non−linear functions, where
accurate deterination of the soft−start timing is impossible.
However, for simplicity, the empirical formula below can
be used to estimate the soft−start time with respect to the
value of the external capacitor.
The NCP1530 series are step−down converters with a
smart control scheme that operates with 600 kHz fixed
Pulse Width Modulation (PWM) at moderate to heavy load
currents, so that high efficiency, noise free output voltage
can be generated. In order to improve the system efficiency
at light loads, this device can be configured to work in
auto−mode. In auto−mode operation, the control unit will
detect the loading condition and switch to power saving
Pulse Frequency Modulation (PFM) control scheme at
light load. With these enhanced features, the converter can
achieve high operating efficiency for all loading
conditions. Additionally, the switching frequency can also
be synchronized to external clock signal in between
600 kHz to 1.2 MHz range. The converter uses peak
current mode PWM control as a core, with the high
switching frequency incorporated. Good line and load
regulation can be achieved easily with small value ceramic
input and output capacitors. Internal integrated
compensation voltage ramp ensures stable operation at all
operating modes. NCP1530 series are designed to support
up to 600 mA output current with cycle−by−cycle current
limit protection.
tSS in s 50 CSS in pF 500 s
Current Mode Pulse−Width Modulation (PWM)
Control Scheme
With the SYN pin (pin 2) connected to VIN, the converter
will set to operate at constant switching frequency PWM
mode. NCP1530 uses peak current mode control scheme to
achieve good line and load regulation. The high switching
frequency, 600 kHz, and a carefully compensated internal
control loop, allows the use of low profile small value
ceramic type input and output capacitor for stable
operation. In current mode operation, the required ramp
function is generated by sensing the inductor current
(ISEN) and comparing with the voltage loop error
amplifier (OTA) output. The OTA output is derived from
feedback from the output voltage pin (VOUT − Pin 6) and
the internal reference voltage (VREF − Pin 7). See Figure 2.
On a cycle−by−cycle basis, the duty cycle is controlled to
keep the output voltage within regulation. The current
mode approach has outstanding line regulation
performance and good overall system stability.
Additionally, by monitoring the inductor current, a
cycle−by−cycle current limit protection is implemented.
Constant Frequency PWM scheme reduces output ripple
and noise, which is one of the important characteristics for
noise sensitive communication applications. The high
switching frequency allows the use of small size surface
mount components that saves significant PC board area and
improves layout compactness and EMI performance.
The Internal Oscillator
The oscillator that governs the switching of the PWM
control cycle is self contained and no external timing
component is required to setup the switching frequency.
For PWM mode and auto−mode operation, all timing
signals required for proper operation are derived from the
internal oscillator. The internal fix frequency oscillator is
trimmed to run at 600 kHz 20% over full temperature
range. In case the device is forced to operate at
Synchronization mode by applying an external clock signal
to SYN pin (pin 2), the external clock signal will supersede
the internal oscillator and take charge of the switching
operation.
Voltage Reference and Soft−Start
An internal high accuracy voltage reference is included
in NCP1530. This reference voltage governs all internal
reference levels in various functional blocks required for
proper operation. This reference voltage is precisely
trimmed to 1.2 V 1.5% over full temperature range. The
reference voltage can be accessed externally at VREF pin
(pin 7), with an external capacitor, CREF of 1.0 F, privding
up to 5.0 mA of loading. Additionally, NCP1530 has a
Soft−Start circuit built around the voltage reference block
that provide limits to the inrush current during start−up by
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NCP1530
Power Saving Pulse−Frequency−Modulation (PFM)
Control Scheme
Output Overvoltage Protection (OVP)
In order to prevent the output voltage from going to high
(when the load current is close to zero in a pure PWM mode
and other abnormal conditions), an Output Overvoltage
protection circuit is included in the NCP1530. In case the
output voltage is higher than its nominal level by more than
12% maximum, the protection circuitry will stop the
switching immediately.
With the SYN pin (pin 2) connected to ground or left
open, the converter will operate in PWM/PFM auto mode.
Under this operating mode, NCP1530 will stay in constant
frequency PWM operation in moderate to heavy load
conditions. When the load decreases down to a threshold
point, the operation will switch to the power saving PFM
operation automatically. The switchover mechanism
depends on the input voltage, output voltage and the
inductor current level. The mode change circuit will
determine whether the converter should be operated in
PWM or PFM mode. In order to maintain stable and smooth
switching mode transition, a small hysteresis on the load
current level for mode transition was implemented. The
detailed mode transition characteristics for each voltage
option are illustrated in Figures 11 and 14. PFM mode
operation provides high conversion efficiency even at very
light loading conditions. In PFM mode, most of the circuits
inside the device will be turned off and the converter
operates just as a simple voltage hysteretic converter.
When the load current increases, the converter returns to
PWM mode automatically.
Internal Thermal Shutdown
Internal thermal shutdown circuitry is provided to
protect the integrated circuit in the event that the maximum
junction temperature is exceeded. The protection will be
activated at about 145°C with a hysteresis of 15°C. This
feature is provided to prevent failures from unexpected
overheating.
Input Capacitor Selection
For a PWM converter operating in continuous current
mode, the input current of the converter is a square wave
with a duty ratio of approximately VOUT/VIN. The
pulsating nature of the input current transient can be a
source of EMI noise and system instability. Using an input
bypass capacitor can reduce the peak current transients
drawn from the input supply source, thereby reducing
switching noise significantly. The capacitance needed for
the input bypass capacitor depends on the source
impedance of the input supply. For NCP1530, a low ESR,
low profile ceramic capacitor of 22 F can be used for most
of the cases. For effective bypass results, the input
capacitor should be placed just next to VIN pin (pin 1)
whenever it is possible.
External Synchronization Control
The NCP1530 has an internal fixed frequency oscillator
of 600 kHz or can be synchronized to an external clock
signal at SYN pin (pin 2). Connecting the SYN pin with an
external clock signal will force the converter to operate in
a pure PWM mode and the switching frequency will be
synchronized. The external clock signal should be in the
range of 600 kHz to 1.2 MHz and the pulse width should
not be less than 300 ns. The detection of the pulse train is
edge sensitive and independent of duty ratio. In the case
where the external clock frequency is too low, the detection
circuit may not be able to follow and will treat it as a
disturbance, thus affecting the converters normal
operation. The internal control circuit detects the rising
edge of the pulse train and the switching frequency
synchronized to the external clock signal. If the external
clock signal ceases for several clock cycles, the converter
will switch back to use the internal oscillator automatically.
Inductor Value Selection
Selecting the proper inductance for the power inductor
is a trade−off between inductor’s physical sizes, transient
response, power delivering capability, output voltage
ripple and power conversion efficiency. Low value
inductor saves cost, PC board space and provides fast
transient response, however suffers high inductor ripple
current, core loss and lower overall conversion efficiency.
The relationship between the inductance and the inductor
ripple current is given by the equation in below.
Power Saving Shutdown Mode
L
NCP1530 can be disabled whenever the EN pin (pin 5)
is tied to ground. In shutdown mode, the internal reference,
oscillator and most of the control circuitries are turned off.
With the device put in shutdown mode, the device current
consumption will be as low as 0.5 A (typ).
TON(VIN RDS(ON) IOUT VF VOUT)
IL_RIPPLE(P P)
Where L is the inductance required;
TON is the nominal ON time within a switching cycle;
RDS(ON) is the ON resistance of the internal MOSFET;
VF is the forward voltage drop of the Schottky diode;
VIN is the worst−case input voltage;
VOUT is the output voltage;
IOUT is the maximum allowed loading current;
IL_RIPPLE(P−P) is the acceptable inductor current ripple
level.
Input Undervoltage Lockout Protection (UVLO)
To prevent the P−Channel MOSFETs from operating
below safe input voltage levels, an Undervoltage Lockout
protection is incorporated in NCP1530. Whenever the
input voltage, VIN drops below approximately 2.0 V, the
protection circuitry will be activated and the converter
operation will be stopped.
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NCP1530
Output Capacitor Selection
For ease of application, the previous equation was
plotted in Figure 35 to help end user to select the right
inductor for specific application. As a rule of thumb, the
user needs to be aware of the maximum peak inductor
current and should be designed not to exceed the saturation
limit of the inductor selected. Low inductance can supply
higher output current, but suffers higher output ripple and
reduced efficiency, but it limits the output current
capability. On the other hand, high inductance can improve
output ripple and efficiency, at the same time, it also limits
the output current capability. One other critical parameter
of the inductor is its DC resistance. This resistance can
introduce unwanted power loss and hence reduce overall
efficiency. The basic rule is selecting an inductor with
lowest DC resistance within the board space limitation.
Selection of the output capacitor, COUT is primarily
governed by the required effective series resistance (ESR)
of the capacitor. Typically, once the ESR requirement is
met, the capacitance will be adequate for filtering. The
output voltage ripple, VRIPPLE is approximated by,
Where FOSC is the switching frequency and ESR is the
effective series resistance of the output capacitor.
From equation in above, it can be noted that the output
voltage ripple is contributed to by two parts. For most of the
cases, the major contributor is the capacitor’s ESR.
Ordinary aluminum−electrolytic capacitors have high ESR
and should be avoided. High quality Low ESR
aluminum−electrolytic capacitors are acceptable and
relatively inexpensive. Low ESR tantalum capacitors are
another alternative. For even better performance, surface
mounted ceramic capacitors can be used. Ceramic
capacitors have lowest ESR among all choices. The
NCP1530 is internally compensated for stable operation
with low ESR ceramic capacitors. However, ordinary
multi−layer ceramic capacitors have poor temperature and
frequency performance, for switching applications, so only
high quality, grade X5R and X7R ceramic capacitors can
be used.
12
L, INDUCTANCE (H)
10
8.0
RDS(ON) = 3.0 D1, MBRM120ET3
CIN = COUT = 22 F
IOUT = 600 mA
IL_RIPPLE(P−P) = 0.2 A
6.0
4.0
2.0
3.0 V
2.5 V
0
3.0
2.7 V
3.5
PCB Layout Recommendations
3.3 V
4.0
1
VRIPPLE IL_RIPPLE(P P) ESR 4 FOSCCOUT
4.5
Good PCB layout plays an important role in switching
mode power conversion. Careful PCB layout can help to
minimize ground bounce, EMI noise and unwanted
feedbacks that can affect the performance of the converter.
Hints suggested below can be used as a guideline in most
situations.
5.0
VIN, INPUT VOLTAGE (V)
Figure 35. Inductor Selection Chart
Flywheel Diode Selection
Grounding
The flywheel diode is turned on and carries load current
during the off time. At high input voltages, the diode
conducts most of the time. In the case where VIN
approaches VOUT, the diode conducts only a small fraction
of the cycle. While the output terminals are shorted, the
diode will be subject to its highest stress. Under this
condition, the diode must be able to safely handle the peak
current circulating in the loop. So, it is important to select
a flywheel diode that can meet the diode peak current and
average power dissipation requirements. Under normal
conditions, the average current conducted by the flywheel
diode is given by,
Star−ground connection should be used to connect the
output power return ground, the input power return ground
and the device power ground together at one point. All high
current running paths must be thick enough for current
flowing through and producing insignificant voltage drop
along the path.
Components Placement
Power components, i.e. input capacitor, inductor and
output capacitor, must be placed as close together as
possible. All connecting traces must be short, direct and
thick. High current flowing and switching paths must be
kept away from the feedback (VOUT, pin 6) terminal to
avoid unwanted injection of noise into the feedback path.
V VOUT
ID IN
IOUT
VIN VF
Where ID is the average diode current and VF is the forward
voltage drop of the diode.
A low forward voltage drop and fast switching diode
must also be used to optimize converter efficiency.
Schottky diodes are a good choice for low forward drop and
fast switching times.
Feedback Path
Feedback of the output voltage must be a separate trace
separated from the power path. The output voltage sensing
trace to the feedback (VOUT, pin 6) pin should be connected
to the output voltage directly at the anode of the output
capacitor.
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NCP1530
ORDERING INFORMATION
Device
Output Voltage
Device Marking
Package
NCP1530DM25R2
2.5 V
DAAA
NCP1530DM27R2
2.7 V
DAAB
NCP1530DM30R2
3.0 V
DAAC
NCP1530DM30R2G
3.0 V
DAAC
Micro8
(Pb−Free)
NCP1530DM33R2
3.3 V
DAAD
Micro8
Shipping†
Micro8
4000 Units
Per 7 Inch 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.
NOTE: The ordering information lists four standard output voltage device options. Additional device with output voltage ranging from 2.5 V to
3.5 V in 100 mV increments can be manufactured. Contact your ON Semiconductor representative for availability.
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NCP1530
PACKAGE DIMENSIONS
Micro8
DM SUFFIX
CASE 846A−02
ISSUE F
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSION A DOES NOT INCLUDE MOLD
FLASH, PROTRUSIONS OR GATE BURRS. MOLD
FLASH, PROTRUSIONS OR GATE BURRS SHALL
NOT EXCEED 0.15 (0.006) PER SIDE.
4. DIMENSION B DOES NOT INCLUDE INTERLEAD
FLASH OR PROTRUSION. INTERLEAD FLASH OR
PROTRUSION SHALL NOT EXCEED 0.25 (0.010)
PER SIDE.
5. 846A−01 OBSOLETE, NEW STANDARD 846A−02.
−A−
−B−
K
PIN 1 ID
G
D 8 PL
0.08 (0.003)
M
T B
S
A
DIM
A
B
C
D
G
H
J
K
L
S
SEATING
−T− PLANE
0.038 (0.0015)
C
L
J
H
SOLDERING FOOTPRINT*
8X
1.04
0.041
0.38
0.015
3.20
0.126
6X
8X
4.24
0.167
0.65
0.0256
5.28
0.208
SCALE 8:1
mm inches
*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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15
MILLIMETERS
MIN
MAX
2.90
3.10
2.90
3.10
−−−
1.10
0.25
0.40
0.65 BSC
0.05
0.15
0.13
0.23
4.75
5.05
0.40
0.70
INCHES
MIN
MAX
0.114
0.122
0.114
0.122
−−−
0.043
0.010
0.016
0.026 BSC
0.002
0.006
0.005
0.009
0.187
0.199
0.016
0.028
NCP1530
Micro8 is a trademark of International Rectifier.
ON Semiconductor and
are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). 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 its officers, employees,
subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, 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
LITERATURE FULFILLMENT:
N. American Technical Support: 800−282−9855 Toll Free
Literature Distribution Center for ON Semiconductor
USA/Canada
P.O. Box 61312, Phoenix, Arizona 85082−1312 USA
Phone: 480−829−7710 or 800−344−3860 Toll Free USA/Canada Japan: ON Semiconductor, Japan Customer Focus Center
2−9−1 Kamimeguro, Meguro−ku, Tokyo, Japan 153−0051
Fax: 480−829−7709 or 800−344−3867 Toll Free USA/Canada
Phone: 81−3−5773−3850
Email: [email protected]
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ON Semiconductor Website: http://onsemi.com
Order Literature: http://www.onsemi.com/litorder
For additional information, please contact your
local Sales Representative.
NCP1530/D