Preliminary
®
SP6659
1.5MHz, 600mA Synchronous Buck Regulator
FEATURES
■ 94% Efficiency Possible
■ 600mA Output Current at VIN = 3V
■ 2.5V to 5.5V Input Voltage Range
■ 1.5MHz constant frequency operation
■ No Schottky Diode Required
■ Output Voltages as low as 0.6V
■ Slope Compensated Current Mode
Operation for Excellent Line and Load
Transient Response
■ 100 % Duty Cycle in LDO Mode
■ <1µA Shutdown Current, Quiescent
Current of 300 µA
■ Over-temperature protected
■ Offered in Low Profile TSOT-23
package
VFB
VIN
5
4
VOUT
VIN
5
4
SP6659
SP6659
5 Pin TSOT-23
5 Pin TSOT-23
1
RUN
1
2
3
GND
SW
RUN
Adjustable
2
3
GND
SW
Fixed
Now Available in Lead Free Packaging
APPLICATIONS
■ Cell Phones
■ Wireless and DSL Modems
■ DSC's
■ Portable Instruments
DESCRIPTION
The SP6659 is a 600mA synchronous buck regulator using a constant frequency, current mode
architecture. The output voltage can be programmed using an external resistor divider. The 2.5V
to 5.5V input voltage range is ideal for portable applications that use a Li-Ion battery. Switching
frequency is internally set at 1.5MHz, allowing the use of small surface mount inductors and
capacitors. The internal synchronous switch increases efficiency and eliminates the need for an
external Schottky diode. The output voltage can be programmed using an external resistor
divider. Low output voltages are easily supported with the 0.6V feedback reference voltage. The
SP6659 is available in a low profile 5 pin TSOT-23 package.
TYPICAL APPLICATION SCHEMATICS
®
®
2.2µH
2.2µH
V IN
3
4
SW
C2
SP6659
4.7µF
Ceramic
RUN
V OUT
22pF
R2
1
5
V FB
4
V IN
4.7µF
10µF
Ceramic Ceramic
SP6659
3
SW
5
V OUT
RUN 1
V OUT
10µF
Ceramic
2
2
R1
GND
GND
Adjustable
Date: 07/20/05
Fixed
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
1
© Copyright 2005 Sipex Corporation
ABSOLUTE MAXIMUM RATINGS
Input Supply Voltage ......................................................... -0.3V to +6V
RUN, VFBVoltages .................................................. -0.3V to (VIN + 0.3V)
SW Voltage ............................................................ -0.3V to (VIN + 0.3V)
P-Channel Switch Source Current ............................................. 800mA
N-Channel Switch Sink Current .................................................. 800mA
Peak Switch Sink and Source Current ........................................... 1.3A
Operating Temperature ................................................. -40°C to +85°C
Storage Temperature ................................................. -65°C to +150 °C
Junction Temperature (Note 1) .................................................. 125 °C
These are stress ratings only and functional operation of the device at
these ratings or any other above those indicated in the operation sections
of the specifications below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may affect reliability.
ELECTRICAL CHARACTERISTICS
Vin=Vrun=3.6V, Io=0mA, Tamb= -40ºC to +85ºC, typical values at 25ºC unless otherwise noted.
Parameter
Input Voltage Range
Min
Typ
2.5
Max
Units
5.5
V
Conditions
Input DC Supply Current
Active Mode
300
400
µA
Shutdown Mode
0.1
1
µA
0.5880
0.6000
0.6120
0.5865
0.6000
0.6135
0.5820
0.6000
0.6180
85
300
nA
Vfb = 1.0V
0.4
1
%/V
Vin = 2.5V to 5.5V
Vfb (Feedback Voltage)
Vfb Input Bias Current
Vfb Line Regulation
Vfb Load Regulation
Regulated Output Voltage
-1
Vfb = 0.5V, Vin = Vrun
Vin = 3.6V, Vrun = ZeroV
Ta=+25ºC
V
0ºC<Ta<+85ºC
-40ºC < Ta < +85ºC
-0.1
0.01
0.1
%/mA
1.455
1.500
1.545
V
SP6659EK1-1.5, -40ºC < Ta < +85ºC
ILoad = 0mA to 600mA
1.746
1.800
1.854
V
SP6659EK1-1.8, -40ºC < Ta < +85ºC
Minimum Output Voltage
0.6
Peak inductor current
0.7
1.15
1.5
A
Oscillator frequency
0.8
1.4
1.8
mHz
P-channel ON resistance
0.4
0.6
Ω
ISW = 100mA
N-channel ON resistance
0.4
0.6
Ω
ISW = -100mA
±0.01
±1.0
µA
1
1.3
V
±0.01
±1.5
µA
SW Leakage Current
Run Threshold Voltage
V
0.2
Run Leakage Current
Vfb = 0.5V
Closed Loop, ILoad=100mA
Vrun=ZeroV, Vin = 3.6V
Vsw=ZeroV, Vsw = Vin
Note 1: Junction Temperature TJ is calculated from the ambient temperature TA and ower dissipation PD
according to the following formula: TJ = TA + PD X 220°C/W
PIN DESCRIPTION
PIN #
PIN NAME
DESCRIPTION
1
RUN
Power down control pin. Forcing this pin above 1.5V enables the device. Forcing this
pin below 0.3V shuts down the device.
2
GND
Ground pin.
3
SW
Switching node.
4
V IN
Power supply pin
Adjustable Version: VFB, Feedback Input Pin. Connect FB to the center point of the
external resistor divider. The feedback threshold voltage is 0.6V.
5
VFB / VOUT
Fixed Output Version: VOUT, Output Voltage Feedback Pin. An internal resistive
divider drops the output voltage down for comparison to the internal reference voltage.
Date: 07/20/05
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
2
© Copyright 2005 Sipex Corporation
TYPICAL PERFORMANCE CHARACTERISTICS
Refer to the typical application schematic, TAMB= +27°C
Figure 2: Load Transient 0mA to 600mA
Figure 1: Fast VIN Startup (Scope: 50µs/div)
CH 1: Switch Node, 5V/ div
CH 1: Output Voltage, 100mV per division ACCoupled
CH 2: Inductor Current, 1A/ div
CH 3: VOUT, 1V/ div
CH 2: Load Current, 500mA/ div
CH 4: VIN, 5V/ div
CH 3: Inductor Current, 500mA/ div
Figure 3: Load Transient 50mA to 650mA
Figure 4: Load Transient 100mA to 700mA
CH 1: Output Voltage, 100mV per division ACCoupled
CH 1: Output Voltage, 100mV per division ACCoupled
CH 2: Load Current, 500mA/ div
CH 2: Load Current, 500mA/ div
CH 3: Inductor Current, 500mA/ div
CH 3: Inductor Current, 500mA/ div
Date: 07/20/05
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
3
© Copyright 2005 Sipex Corporation
TYPICAL PERFORMANCE CHARACTERISTICS
SP6659 Efficiency vs. Load Current
VOUT = 1.2V
Efficiency (%)
100
90
80
Vin = 2.7V
70
Vin = 3.3V
60
Vin = 4.2V
50
40
1
10
100
1000
Load Current (mA)
Figure 5: Efficiency Vs. Load Current, Vout =1.2V
SP6659 Efficiency vs. Load Current
VOUT = 1.8V
100
Efficiency (%)
90
80
Vin = 2.7V
Vin = 3.3V
Vin = 4.2V
70
60
50
40
1
10
100
1000
Load Current (mA)
Figure 6: Efficiency Vs. Load Current, Vout =1.8V
Date: 07/20/05
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
4
© Copyright 2005 Sipex Corporation
FUNCTIONAL DIAGRAMS
SLOPE
COMP
OSC
VIN
2.7 - 5.5V
4
+
CIN
+
BLANKING
-
ISENSE
COMP
R
-
VOUT
0.6V
+
EA
-
Q
_
Q
RS LATCH
PWM
LOGIC
R1
0.65V
DRV
+
OV
DET
-
R2
SW
NONOVERLAP
CONTROL
5
_
S
_
R
+
COMP
-
COUT
+
Izero
COMP
-
VIN
RUN
2
GND
0.6V
REF
1
VOUT
3
SHUTDOWN
Fixed Output Version
SLOPE
COMP
OSC
4
+
BLANKING
+
-
CIN
ISENSE
COMP
VIN
2.7 - 5.5V
R
-
VFB
0.6V
0.65V
+
COMP
-
Q
_
Q
RS LATCH
+
OV
DET
-
PWM
LOGIC
DRV
+
Izero
COMP
-
VIN
RUN
REF
1
NONOVERLAP
CONTROL
5
+
EA
-
_
S
_
R
SW
VOUT
3
C2
R1
COUT
R2
2
GND
0.6V
SHUTDOWN
Adjustable Output Version
Date: 07/20/05
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
5
© Copyright 2005 Sipex Corporation
APPLICATION INFORMATION
V OUT
®
R2
A resistive divider based on the following
equation determines the output voltage:
VOUT = 0.6 (1+
SP6659
V FB
R1
R2
)
R1
GND
The external resistive divider is connected
to the output as shown in Figure 7 .
Figure 7: Setting the SP6659 Output Voltage.
THEORY OF OPERATION
The SP6659 is a monolithic switching mode
Step-Down DC-DC converter. It utilizes internal MOSFETs to achieve high efficiency
and can generate very low output voltage
by using its internal reference at 0.6V. It
operates at a fixed switching frequency,
and uses slope compensated, current-mode
architecture. This Step-Down DC-DC converter supplies 600mA of output current at
VIN = 3V. The entire input voltage range is
from 2.5V to 5.5V.
current comparator, ICOMP, limits the peak
inductor current. When the main switch is
off, the synchronous rectifier will be turned
on immediately and stay on until either the
inductor current starts to reverse, as indicated by the current reversal comparator,
IZERO, or the beginning of the next clock
cycle. The OVDET comparator controls
output transient overshoots by turning the
main switch off and keeping it off until the
fault is no longer present.
__________________ CURRENT MODE
PWM CONTROL
_______________________ IDLE MODE
OPERATION
Slope compensated current mode PWM
control provides stable switching and cycleby-cycle current limit for excellent load and
line responses and protection of the internal
main switch (P-Channel MOSFET) as well
as the synchronous rectifier (N-Channel
MOSFET). During normal operation, the internal P-Channel MOSFET is turned on for
a certain time to ramp the inductor current at
each rising edge of the internal oscillator,
and switched off when the peak inductor
current is above the error voltage. The
At very light loads, the SP6659 automatically enters Idle Mode (Figure 8). In the Idle
Mode, the inductor current may reach zero
Amps or reverse on each pulse. The PWM
control loop will automatically skip pulses to
maintain output regulation. The bottom
MOSFET is turned off by the current reversal comparator, IZERO, and the switch voltage will ring. This is discontinuous mode
operation, and is normal behavior for the
switching regulator.
Date: 07/20/05
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
6
© Copyright 2005 Sipex Corporation
THEORY OF OPERATION
_______________________ DROPOUT
OPERATION
________________________ MAXIMUM
LOAD CURRENT
When the input voltage decreases toward
the value of the output voltage, the SP6659
allows the main switch to remain on for more
than one switching cycle and increases the
duty cycle until it reaches 100%.
The SP6659 will operate with an input supply voltage as low as 2.5V, however, the
maximum load current decreases at lower
inputs due to a large IR drop on the main
switch and synchronous rectifier. The slope
compensation signal reduces the peak inductor current as a function of the duty cycle
to prevent sub-harmonic oscillations at duty
cycles greater than 50%. Conversely, the
current limit increases as the duty cycle
decreases.
The duty cycle D of a step-down converter is
defined as:
D = TON X
ƒOSC
X 100%
≈ VOUT
X 100%
VIN
_______________________ INDUCTOR
SELECTION
For most designs, the SP6659 operates with
inductors of 1µH to 4.7µH. Low inductance
values are physically smaller but require
faster switching, which can result in some
efficiency loss. The inductor value can be
derived from the following equation:
L = VOUT X (VIN - VOUT)
VIN X ∆IL X ƒOSC
Figure 8. SP6659 Idle Mode Operation
Where ∆IL is the inductor Ripple Current.
Large value inductors lower ripple current
and small value inductors result in higher
ripple current. Choose inductors at ripple
current of approximately 35% of the maximum load current 600mA, or ~ 210mA.
where TON is the main switch on time, and
ƒOSC is the oscillator frequency (1.5Mhz).
The output voltage then is the input voltage
minus the voltage drop across the main
switch and the inductor. At low input supply
voltage, the R DSON of the P-Channel
MOSFET increases, and the efficiency of
the converter decreases. Caution must be
exercised to ensure that the heat dissipated
does not exceed the maximum junction temperature of the IC.
Date: 07/20/05
For output voltages above 2.0V, when lightload efficiency is important, the minimum
recommended inductor is 2.2µH. For optimum voltage-positioning load transients,
choose an inductor with DC series resistance in the 50mΩ to 150mΩ range. For
higher efficiency at heavy loads (above
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
7
© Copyright 2005 Sipex Corporation
THEORY OF OPERATION
________________ INPUT CAPACITOR
SELECTION
200mA), or minimal load regulation (but
some transient overshoot), the resistance
should be kept below 100mΩ. The DC current rating of the inductor should be at least
equal to the maximum load current plus half
the ripple current to prevent core saturation
(600mA+105mA).
The input capacitor reduces the surge current drawn from the input and switching
noise from the device. The input capacitor
impedance at the switching frequency shall
be less than input source impedance to
prevent high frequency switching current
from passing to the input. A low ESR (Equivalent Series Resistance) input capacitor sized
for maximum RMS current must be used.
Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of
their low ESR and small temperature coefficients. A 4.7µF ceramic capacitor for most
applications is sufficient.
Table 1 lists some typical surface mount
inductors that meet target applications for
the SP6659.
Part #
Sumida
CR43
L
(µH)
Max
DCR
(mΩ)
Rated
DC
Current
(Amps)
1.4
56.2
2.52
2.2
71.2
1.5
3.3
86.2
1.44
4.7
108.7
1.15
2.2
75
1.32
3.3
110
1.04
4.7
162
0.84
1.5
120
1.29
2.2
140
1.14
3.3
180
0.98
4.7
240
0.79
Size WxLxH
(mm)
______________ OUTPUT CAPACITOR
SELECTION
4.5x4.0x3.5
The output capacitor is required to keep the
output voltage ripple small and to ensure
regulation loop stability. The output capacitor must have low impedance at the switching frequency. Ceramic capacitors with X5R
or X7R dielectrics are recommended due to
their low ESR and high ripple current. The
output ripple ∆VOUT is determined by:
1.5
Sumida
CDRH4D18
Toko
D312C
4.7x4.7x2.0
3.6x3.6x1.2
Table 1: Typical Surface Mount Inductors
∆VOUT ≤
VOUT X (VIN - VOUT)
VIN X L X ƒOSC
Date: 07/20/05
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
8
+
X ESR
{
1
(8X ƒOSC X COUT)
}
© Copyright 2005 Sipex Corporation
PACKAGE: 5 PIN TSOT23
D
e1
N
N/2
+1
E/2
E1/2
B
E
E1
B
SEE VIEW C
VIEW A-A
INDEX AREA
(D/2 X E1/2)
1
2
N/2
e
Ø1
b
Gauge Plane
Seating Plane
ø1
L
ø
L1
VIEW C
5 Pin TSOT JEDEC MO-193 (AB) Variation
MIN
NOM
MAX
SYMBOL
A
1.1
A1
0
0.1
A2
0.7
0.9
1
b
0.3
0.5
c
0.08
0.2
2.90 BSC
D
0.95 BSC
e
1.90 BSC
e1
2.80 BSC
E
1.60 BSC
E1
L
0.3
0.45
0.6
0.60 REF
L1
0.25 BSC
L2
ø
0º
4º
8º
ø1
4º
10º
12º
A2
A
SEATING PLANE
C
SIDE VIEW
A1
WITH PLATING
b
c
Note: Dimensions in (mm)
BASE METAL
Section B-B
____________________________ THERMAL
RESISTANCE
Thermal Resistance is specified with approximately 1 square of 1 ounce of copper.
OJA .......................................................................220°C/W
OJC .......................................................................110°C/W
Date: 07/20/05
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
9
© Copyright 2005 Sipex Corporation
ORDERING INFORMATION
Part Number
Operating Temperature Range
Package Type
SP6659EK1 ......... ...............................-40°C to +85°C ........................................................... 5 Pin TSOT23
SP6659EK1/TR .... ...............................-40°C to +85°C ........................................................... 5 Pin TSOT23
SP6659EK1-1.5 .... ...............................-40°C to +85°C ........................................................... 5 Pin TSOT23
SP6659EK1-1.5/TR...............................-40°C to +85°C .......................................................... 5 Pin TSOT23
SP6659EK1-1.8 .... ...............................-40°C to +85°C ........................................................... 5 Pin TSOT23
SP6659EK1-1.8/TR...............................-40°C to +85°C .......................................................... 5 Pin TSOT23
Available in lead free packaging. To order add "-L" suffix to part number.
Example: SP6659EK1/TR = standard; SP6659EK1-L/TR = lead free
/TR = Tape and Reel
Pack quantity is 2,500 for TSOT23.
Corporation
ANALOG EXCELLENCE
Sipex Corporation
Headquarters and
Sales Office
233 South Hillview Drive
Milpitas, CA 95035
TEL: (408) 934-7500
FAX: (408) 935-7600
Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the
application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others.
Date: 07/20/05
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
10
© Copyright 2005 Sipex Corporation