SP6648UEB Exar Corporation, SP6648UEB Datasheet - Page 4

• Manufacturer Part Number: SP6648UEB
• Description: Power Management Modules & Development Tools Ultra Low Quies Cur Hi-Eff Boost Reg
• Manufacturer: Exar Corporation
• Type: DC/DC Switching Converters, Regulators & Controllersr

Specifications of SP6648UEB

• Product: Power Management Modules

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
SHDN
R
LBI
FB
LIM
SDI
0.61V
Ipkset
INTERNAL
Ref
Block
V
BATT
current
control
-
+
V
c
SDI
BATT
n
IBIAS
0.61V
0.61V
current
reference
+
-
1.25V
c
-
+
c
V
BATT
V
O
REF
FB
SP6648 Ultra-low Quiescent Current, High Efficiency Boost Regulator
UVLO
Min
T
+
-
OFF
c
T
VOLOW
OFF
R
S
Q
Qn
SP6648
CHARGE
4
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
and a maximum on-time (t
t
t
K
K
OFF
ON
ON
OFF
switch
buffer
≤
charge end
≥
= 4.0V
IUC
K
= 1.0V
K
QKILL
NMOS
ON
OFF
QKILL
PMOS
/ V
μ
/ (V
μ
s.
reference
BATT
s and
LX
current
LX
THEORY OF OPERATION
OUT
FUNCTIONAL DIAGRAM
V
BATT
with
undercurrent
comparator
- V
V
O
SWITCH GROUND
overcurrent
comparator
INTERNAL
SUPPLY
+
-
Max
Ton
c
BATT
INTERNAL
GROUND
ON
,
) and
© 2006 Sipex Corporation
MAX
P
) where:
GND
V
GND
OUT
LBON
OFF
,
LOAD
MIN
)