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PDF SS6612 Data sheet ( Hoja de datos )
| Número de pieza | SS6612 | |
| Descripción | High-Efficiency Synchronous Step-up DC/DC Converter | |
| Fabricantes | Silicon Standard | |
| Logotipo |  |
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SS6612
High-Efficiency Synchronous Step-up DC/DC
Converter with Selectable Current Limit
FEATURES
High efficiency (93% with VIN=2.4V, VOUT= 3.3V,
IOUT=200mA)
Output current up to 500mA. (VIN=2.4V, at
VOUT=3.3V, CLSEL=OUT)
Quiescent supply current of 20µA
Power-saving shutdown mode (0.1µA typical).
Internal synchronous rectifier (no external diode
required).
Selectable current limit for reduced ripple.
Low-noise, anti-ringing feature.
On-chip low-battery detector.
Low-battery hysteresis.
Space-saving package: MSOP-10
APPLICATIONS
Palmtop & Notebook Computers.
PDAs
Wireless Phones
Pocket Organizers.
Digital Cameras.
Hand-Held Devices with 1 to 3 Cells of
NiMH/NiCd Batteries.
DESCRIPTION
The SS6612 is a high-efficiency step-up
DC/DC converter, with a start-up voltage as low
as 0.8V, and an operating voltage down to 0.7V.
Consuming only 20µA of quiescent current,
this device includes a built-in synchronous rec-
tifier that reduces size and cost by eliminating
the need for an external Schottky diode, and
improves overall efficiency by minimizing
losses.
The switching frequency can range up to
500KHz depending on the load and input volt-
age. The output voltage can be easily set; by
two external resistors for 1.8V to 5.5V; con-
necting FB to OUT to get 3.3V; or connecting
to GND to get 5.0V. For additional design flexibil-
ity, the peak current of the internal switch is
selectable (0.65A or 1.0A). The SS6612 also
features a circuit that eliminates noise caused
by inductor ringing.
TYPICAL APPLICATION CIRCUIT
VIN
ON OFF
Selectable Current Limit
(1.0A or 0.65A)
Low Battery
Detection
+
47µF
SHDN
200Ω
BATT
LX
CLSEL
OUT
SS6612
LBI LBO
REF GND FB
0.1µF
22µH
Output 3.3V, 5.0V
+
or Adj. (1.8V to
5.5V) up to 300mA
47µF
Low-battery
Detect Out
Rev.2.02 12/06/2003
www.SiliconStandard.com
1 of 16
1 page  
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SS6612
TYPICAL PERFORMANCE CHARACTERISTICS
160
140
120
100
VOUT=5V (FB=GND)
80
60
40
20 VOUT=3.3V (FB=OUT)
0
0.0
Fig. 1
0.5 1.0 1.5 2.0 2.5 3.0
Input battery voltage (V)
No-Load Battery Current vs. Input Battery
3.5
1.8
1.6
1.4 VOUT=5V (FB=GND)
1.2
1.0
0.8
0.6
0.4 VOUT=3.3V (FB=OUT)
0.2
0.0 0.01
Fig. 3
0.1 1 10
Output Current (mA)
100
Start-Up Voltage vs. Output Current
100
90
80
70 VIN=1.2V
60
50 VIN=2.4V
40 VIN=3.6V
30
20 VOUT=5V (FB=GND)
10 CLSEL=OUT (ILIMIT =1A)
0
0.01
Fig. 5
0.1 1 10 100 1000
Output Current (mA)
Efficiency vs. Output Current (ref. to Fig.35)
0.5
0.4
0.3
0.2
0.1
0.01.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Supply Voltage (V)
Fig. 2 Shutdown Current vs. Supply Voltage
5.5
400
L=22µH
350 CIN=100µF
300 COUT=100µF
250
200 VOUT=3.3V (FB=OUT)
150
100
VOUT=5.0V (FB=GND)
50
0
0.5 1.0
Fig. 4
1.5 2.0 2.5 3.0 3.5 4.0 4.5
Input Voltage (V)
Turning Point between CCM & DCM
5.0
220
200 CLSEL=OUT (ILIMIT =1A)
180
160
140 VIN=3.6V
120
100
80
60 VIN=2.4V
40
20 VIN=1.2V
VOUT=5.0V
L=22µH
CIN=47µF
COUT=47µF
0
0 50 100 150 200 250 300 350 400 450 500 550 600 650
Output Current (mA)
Fig. 6 Ripple Voltage (ref. to Fig.35)
Rev.2.02 12/06/2003
www.SiliconStandard.com
5 of 16
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SS6612
PIN DESCRIPTIONS
PIN 1: FB- Connected to OUT to get +3.3V
output, connected to GND to get
+5.0V output, or using a resistor
network to set output voltage rang-
ing from +1.8V to +5.5V.
PIN 2: LBI- Low-battery comparator input inter-
nally set at +1.23V to trip.
PIN 3: LBO- Open-drain low battery comparator
output. Output is low when VLBI is
<1.23V. LBO is high impedance
during shutdown.
PIN 4:CLSEL-Current-limit select input. CLSEL=
OUT sets the current limit to 1.0A.
CLSEL=GND sets the current limit
to 0.65A.
APPLICATION INFORMATION
Overview
The SS6612 is a high-efficiency, step-up DC/DC
converter, featuring a built-in synchronous
rectifier, which reduces size and cost by eliminating
the need for an external Schottky diode. The start-up
voltage of the SS6612 is as low as 0.8V and it operates
with an input voltage down to 0.7V. Quiescent supply
current is only 20µA. In addition, the SS6612 features a
circuit that eliminates inductor ringing to reduce
noise. The internal P-MOSFET on-resistance is typi-
cally 0.3Ω to improve overall efficiency by minimizing
AC losses. The output voltage can be easily set; by
two external resistors for 1.8V to 5.5V; connecting
FB to OUT to get 3.3V; or connecting to GND to get
5.0V. The CLSEL pin offers a selectable current
limit (1.0A or 0.65A). The lower current limit allows
the use of a physically smaller inductor in space-
sensitive applications.
PFM Control Scheme
A key feature of the SS6612 is a unique minimum-
off-time, constant-on-time, current-limited, pulse-
frequency-modulation (PFM) control scheme (see
PIN 5: REF- 1.23V reference voltage. Bypass
with a 0.1µF capacitor.
PIN 6: SHDN- Shutdown input. High=operating,
low=shutdown.
PIN 7: BATT- Battery input and damping
switch connection. If damping
switch is unused, leave BATT
unconnected.
PIN 8: GND- Ground.
PIN 9: LX- N-channel and P-channel power
MOSFET drain.
PIN 10: OUT- Power output. OUT provides
bootstrap power to the IC.
BLOCK DIAGRAM) with ultra-low quiescent current.
The peak current of the internal N-MOSFET power
switch is selectable. The switch frequency depends
on either loading conditions or input voltage, and can
range up to 500KHz. It is governed by a pair of one-
shots that set a minimum off-time (1µs ) and a
maximum on-time (4µs ).
Synchronous Rectification
Using the internal synchronous rectifier eliminates
the need for an external Schottky diode, reducing
the cost and board space. During the cycle of off-
time, the P-MOSFET turns on and shuts the N-
MOSFET off. Due to the low turn-on resistance
of the MOSFET, the synchronous rectifier signifi-
cantly improves efficiency without an additional ex-
ternal Schottky diode. Thus, the conversion effi-
ciency can be as high as 93%.
Reference Voltage
The reference voltage (REF) is nominally 1.23V for
excellent T.C. performance. In addition, the REF pin can
source up to 100µA to an external circuit with good load
Rev.2.02 12/06/2003
www.SiliconStandard.com
11 of 16
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet SS6612.PDF ] | |
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