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SP6648
Ultra-low Quiescent Current,
High Efficiency Boost Regulator
FEATURES
■
Ultra-low 12μA Quiescent Current
■
400mA Output Current at 2.6V Input: 3.3V
OUT
■
94% Efficiency from 2 Cell to 3.3V
OUT
■
Wide Input Operating Voltage: 0.85V to 4.5V
■
3.3V Fixed or Adjustable Output
■
Integrated Synchronous Rectifier: 0.3Ω
■
0.3Ω Switch
■
Anti-Ringing Switch Technology
■
Programmable Inductor Peak Current
■
Logic Shutdown Control
■
Under Voltage Lock-Out at 0.61V
■
Programmable Low-Battery Detect
■
Single or Dual Cell Alkaline
■
Small 10 pin DFN Package and Industry
Standard 10 pin MSOP
VBATT
LBI
LBON
RLIM
SHDN
1
2
3
4
5
SP6648
10 Pin DFN
10 V
OUT
9 LX
8 P
GND
7 GND
6 FB
Now Available in Lead Free Packaging
APPLICATIONS
■
Camera Flash LED Driver
■
Wireless Mouse
■
PDA's
■
Pagers
■
Medical Monitors
■
Handheld Portable Devices
■
MP3 Players
DESCRIPTION
The SP6648 is an ultra-low quiescent current, high efficiency step-up DC-DC converter ideal for
single cell, dual cell alkaline and Li-Ion battery applications such as digital still cameras, PDAs,
MP3 players, and other portable devices. The SP6648 combines the high-load efficiency
associated with PWM control, with the low quiescent current and excellent light-load efficiency
of PFM control. The SP6648 features 12μA quiescent current, synchronous rectification, a 0.3Ω
charging switch, anti-ringing inductor switch, programmable low-battery detect, under-voltage
lockout and programmable inductor peak current. The device can be controlled by a 1nA active
LOW shutdown pin.
TYPICAL APPLICATION CIRCUIT
500
10μH
V
BATT
+
47μF
1
LBI
LBON
2
3
4
SHDN
1.87K
V
BATT
LBI
LBON
R
LIM
V
OUT
10
LX 9
P
GND
8
GND 7
FB 6
1μF
205K
47pF
+
47μF
3.3V
OUT
Io (mA)
450
400
350
SP6648
300
250
200
150
100
Vout=3.3V, Ipk=0.85A
50
0
Vout=5.0V, Ipk=0.85A
1.5
2.0
2.5
3.0
Vin (V)
3.5
4.0
4.5
5 SHDN
124K
1.0
Maximum Load Current in Operation
Date: 6/7/06 Rev B
SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
© 2006 Sipex Corporation
1
ABSOLUTE MAXIMUM RATINGS
LX, Vo, V
BATT
, LBON, FB to GND pin ................................ -0.3 to 6.0V
SHDN, LBI ........................................................... -0.3V to V
BATT
+1.0V
Vo, GND, LX Current ....................................................................... 2A
Reverse V
BATT
Current .............................................................. 220mA
Forward V
BATT
Current .............................................................. 500mA
Storage Temperature .................................................. -65
°C
to 150°C
Operating Temperature ................................................ -40°C to +85°C
ESD Rating ........................................................................ 1.5kV HBM
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 SPECIFICATIONS
V
BATT
=V
SHDN
= 2.6V, V
FB
=0.0V, I
LOAD
= 0mA, T
AMB
= -40°C to +85°C, V
OUT
= +3.3V, typical values at 27°C unless
otherwise noted. The
♦
denotes the specifications which apply over full operating temperature range -40°C to +85°C, unless
otherwise specified.
PARAMETER
Input Voltage Operating Range, V
BATT
Output Voltage Range, V
OUT
Start-up Input Voltage, V
BATT
Under Voltage Lock-out/UVLO
Output Voltage, V
O
Quiescent Current into V
O
, I
QO
Quiescent Current into V
BATT
, I
QB
Shutdown Current into V
O,
I
SDO
Shutdown Current into V
BATT,
I
SDB
Efficiency
Inductor Current Limit, I
PK
= 1600/R
LIM
650
1300
0.5
3.12
MIN
0.7
2.5
0.85
0.61
3.30
12
250
1
250
84
92
800
1600
100
200
150
400
Minimum Off-Time Constant K
OFF
Maximum On-Time Constant K
ON
Enable Valid to Output Stable
NMOS Switch Resistance
PMOS Switch Resistance
FB Set Voltage, V
FB
FB Input Current
LBI Falling Trip Voltage
LBI Hysteresis
Low Output Voltage for LBON, V
OL
Leakage current for LBON
SHDN Input Voltage, Note 1
V
IL
V
IH
V
IL
V
IH
SHDN Input Current
LX Pin Leakage
0.56
1.19
0.5
2.5
1.0
4.0
300
0.30
0.30
1.25
1
0.61
25
0.4
1
0.25
1.0
0.5
2.0
1
100
3
nA
μA
V
1.5
5.5
500
0.6
0.6
1.31
100
0.66
1000
2000
TYP
MAX
4.5
5.5
1.1
0.7
3.48
25
750
500
750
UNITS
V
V
V
V
V
μA
nA
nA
nA
%
%
mA
mA
mA
mA
mA
mA
V*μs
V*μs
μs
Ω
Ω
V
nA
V
mV
V
μA
♦
♦
♦
♦
♦
♦
♦
V
BATT
= 1.3V, I
SINK
= 1mA
V
BATT
= 1.3V, V
LBON
= 3.3V
V
BATT
= 1.3V
V
BATT
= 1.3V
V
BATT
= 2.6V
V
BATT
= 2.6V
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
Internal Feedback Divider
V
OUT
= 3.3V, V
FB
= 1.5V, Toggle SHDN
V
OUT
= 3.3V, V
FB
= 1.5V
V
SHDN
= 0.0V
V
SHDN
= 0.0V, V
BATT
= 2.6V
V
BATT
= 1.3V, I
OUT
= 100mA, R
LIM =
2kΩ
V
BATT
= 2.6V, I
OUT
= 200mA, R
LIM =
2kΩ
R
LIM
= 2kΩ
R
LIM
= 1kΩ
V
BATT
= 1.3V, R
LIM
= 4kΩ
V
BATT
= 2.6V, R
LIM
= 4kΩ
V
BATT
= 1.3V, R
LIM
=2kΩ
V
BATT
= 2.6V, R
LIM
=2kΩ
K
OFF
≤
T
OFF
(V
OUT
- V
BATT
)
K
ON
≥
T
ON
(V
BATT
)
I
LOAD
= 1mA
I
NMOS
= 100mA
I
PMOS
= 100mA
External feedback
V
FB
=1.3V
R
LOAD
= 3kΩ
CONDITIONS
After Startup
Output Current
Note 1:
SHDN must transition faster than 1V/100mS for proper operation.
Date: 6/7/06 Rev B
SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
© 2006 Sipex Corporation
2
PIN DESCRIPTION
PIN NUMBER
1
PIN NAME
V
BATT
DESCRIPTION
Battery Voltage. The startup circuitry is powered by this pin. Battery
Voltage is used to calculate switch off time: t
OFF
= K
OFF
/ (V
OUT
- V
BATT
).
When the battery voltage drops below 0.61V the SP6648 goes into an
undervoltage lockout mode (UVLO), where the part is shut down.
2
LBI
Low Battery Input. LBI below 0.61V causes the SP6648 pin to pull LBON
pin down to ground. Use a resistor divider to program the low voltage
threshold for a specific battery configuration.
3
LBON
Low Battery Output Not. Open drain NMOS output that sinks current to
ground when LBI is below 0.61V.
Current Limit Resistor. By connecting a resistor R
LIM
from this pin to
ground the inductor peak current is set by I
PEAK
=1600/R
LIM
. The range for
R
LIM
is 9kΩ (for 180mA) to 1.KΩ (for 1.6A).
Shutdown Not. Tie this pin high to V
BATT,
for normal operation. Pull this
pin to ground to disable all circuitry inside the chip. In shutdown the
output voltage will float down to a diode drop below the battery voltage.
Feedback. Connect this pin to GND for fixed +3.3V operation. Connect
this pin to a resistor voltage divider between V
OUT
and GND for
adjustable output operation.
Ground. Connect to ground plane.
Power Ground. The inductor charging current flows out of this pin.
Inductor Switching Node. Connect one terminal of the inductor to the
positive terminal of the battery. Connect the second terminal of the
inductor to this pin. The inductor charging current flows into LX, through
the internal charging N-channel FET, and out the PGND pin.
Output Voltage. The inductor current flows out of this pin during switch
off-time. It is also used as the internal regulator voltage supply. Connect
this pin to the positive terminal of the output capacitor.
4
R
LIM
5
SHDN
6
FB
7
8
9
GND
PGND
LX
10
V
OUT
Date: 6/7/06 Rev B
SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
© 2006 Sipex Corporation
3
FUNCTIONAL DIAGRAM
V
BATT
QKILL
LX
charge end
V
O
V
BATT
Min
T
OFF
-
UVLO
R
Q
CHARGE
switch
buffer
T
OFF
IUC
undercurrent
comparator
INTERNAL
V
BATT
+
c
-
INTERNAL
SUPPLY
QKILL
PMOS
V
BATT
NMOS
V
O
V
OUT
SHDN
SDI
0.61V
+
c
Max
Ton
V
O
n
SDI
Ref
Block
IBIAS
1.25V
REF
FB
0.61V
+
-
c
+
-
c
VOLOW
S
Qn
LX
current
reference
+
-
c
LOAD
VO
overcurrent
comparator
FB
R
LIM
LBI
0.61V
Ipkset
current
control
current
reference
SWITCH GROUND
INTERNAL
GROUND
P
GND
GND
LBON
-
+
c
SP6648
THEORY OF OPERATION
Detailed Description
The SP6648 is a step-up DC-DC converter that
can start up with input voltages as low as 0.85V
(typically) and operates with an input voltage
down to 0.61V. Ultra low quiescent current of
12μA provides excellent efficiency, up to 94%.
In addition to the main switch, a 0.3Ω internal
MOSFET the SP6648 has an internal synchro-
nous rectifier, increasing efficiency and reduc-
ing the space requirements of an external diode.
An internal inductive-damping switch signifi-
cantly reduces inductive ringing for low-noise,
high efficiency operation. If the supply voltage
drops below 0.61V the SP6648 goes into under
voltage lock-out mode, thus opening both inter-
nal switches. An externally programmable low
battery detector with open drain output provides
the ability to flag a battery-low condition. The
inductor peak current is externally program-
mable to allow for a range of inductor values.
Date: 6/7/06 Rev B
Control Scheme
A minimum off-time, current limited pulse fre-
quency modulation (PFM) control scheme com-
bines the high output power and efficiency of a
pulse width modulation (PWM) device with the
ultra low quiescent current of the traditional
PFM. At low to moderate output loads, the PFM
control provides higher efficiency than tradi-
tional PWM converters are capable of deliver-
ing. At these loads, the switching frequency is
determined by a minimum off-time (t
OFF
,
MIN
)
and a maximum on-time (t
ON
,
MAX
) where:
t
OFF
≥
K
OFF
/ (V
OUT
- V
BATT
) and
t
ON
≤
K
ON
/ V
BATT
with
K
OFF
= 1.0V
μ
s and
K
ON
= 4.0V
μ
s.
SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
© 2006 Sipex Corporation
4
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