SGS Thomson Microelectronics L6920D Datasheet
L6920
1V HIGH EFFICIENCY SYNCRONO US STEP UP CONVERTER
■ 0.6 TO 5.5V OPERATING IN PUT VOLTA GE
■ 1V START UP INPUT VOLTAGE
■ INTERNAL SYNCHRONOUS RECTIFIER
■ ZERO SHUT DOWN CURRENT
■ 3.3V AND 5V FIXED OR ADJUSTABLE
OUTPUT VOLTAGE (2V UP TO 5.2V)
■ 120mΩ INTERNAL ACTIVE SWITCH
■ LOW BATTERY VOLTAGE DETECTION
■ REVERSE BATTERY PROTECTION
ORDERING NUMBER: L6920D
TSSOP8
Applications
■ ONE TO THREE CELL BATTERY DEVICES
■ PDA AND HAND HELD INSTRUMENTS
■ CELLULAR PHONES - DIGITAL CORDLESS
PHONE
■ PAGERS
■ GPS
■ DIGITAL CAMERAS
APPLICATION CIRCUIT
L1
V
CC
2.5V 3.3V
C2
LX
SHDN
7
5
L6920
DESCRIPTION
The L6920 is a high efficiency step-up controller requiring only three external components to realize the
conversion from the battery voltage to the selected
output voltage.
The start up is guaranteed at 1V and the dev ice is operating down to 0.6V.
Internal synchronous rectifier is implemented with a
120m
Ω
P-channel MOSFET and, in order to i mpr ove
the efficiency, a variable frequency control is implemented.
OUT
8
V
OUT
FB
1
500mA
C3 C1
May 2003
LBI
REF
2
3
LBO
GND
4
6
D00IN1136C
1/12
L6920
8
PIN DESCRIPTION
Pin Name Function
1FB
Output voltage selector. Connect FB to GND for Vout=5V or to OUT for Vout=3.3V. Connect FB to an
external resistor divider for adjustable output voltage (from 2V to 5.2V) [see R4 and R5, fig. 7].
2 LBI Battery low voltage detector input. The internal threshold is set to 1.23V.
A resistor divider is needed to adjust the desired low battery threshold:
R1
V
1.23V= 1
LBI
3
LBO
Battery low voltage detector output. If the voltage at the LBI pin drops below the internal
------- -+
⋅
[see R1 and R2, fig. 7]
R2
threshold typ. 1.23V, LBO goes low.
LBO is an open drain output and so a pull-up resistor (about 200KΩ) has to be added for
The
correct output setting [see R3, fig. 7].
4 REF 1.23V reference voltage. Bypass this output to GND with a 100nF capacitor for filtering high
frequency noise. No capacitor is required for stability
5
SHDN
Shutdown pin. When pin 5 is below 0.2V the device is in shutdown, when pin 5 is above 0.6V the
device is operating.
6 GND Ground pin
7 LX Step-up inductor connection
8 OUT Power OUTPUT pin
PIN CONNECTION (Top vi ew)
FB
LBI
LBO
REF
8
2
3
4
TSSOP
7
6
5
OUT1
LX
GND
SHDN
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Value Unit
V
ccmax
Vcc to GND 6 V
LBI, SHDN, FB to GND 6 V
V
out max
Vout to GND 6 V
THERMAL DATA
Symbol Parameter Value Unit
R
th j-amb
T
Thermal Resistance Junction to Ambient 250 °C/W
Maximum Junction Temperature 150 °C
j
2/12
L6920
ELECTRICAL CHARACTERISTCS
(Vin = 2V, FB = GND, T
= -40°C to 85°C and Tj < 125°C unless other-
amb
wise specified))
Symbol Parameter Test Condition Min. Typ. Max. Unit
SECTION
V
CC
in
in
I
q
I
sd
on-N
on-P
Minimum operating Input Voltage 0.6 V
Minimum Start Up Input Voltage 1 V
Quiescent Current Il =0 mA, FB = 1.4V, V
LBI = SHDN = 2V, Tj = T
I
=0 mA, FB = 1.4V, V
l
LBI = SHDN = 2V, Tj = T
= 3.3V
out
amb
= 5V
out
amb
915µA
11 18 µA
Shut Down Current Vin = 5V, Il =0 mA 0.1 5 µA
amb
0.1 2 µA
Active switch ON resistance 120 250 mΩ
Synchronous switch ON
120 250 mΩ
resistance
V
V
Irev Reverse battery current Vin = -4V, Tj = T
POWER SECTION
R
R
CONTROL SECTION
Vout Output voltage FB = OUT, Il =0 mA 3.2 3.3 3.4 V
FB = GND, Il =0 mA 4.9 5 5.1 V
Output voltage range External divider 2 5.2 V
V
V
I
T
onmax
T
offmin
SHDN SHDN logic LOW
V
LBI threshold 1.18 1.23 1.27 V
LBI
0°C < T
LBO logic LOW
LBO
LX switch current limit 0.8 1 1.2 A
lim
I
Maximum on time V
Minimum off time V
SHDN logic HIGH
Reference Voltage 1.18 1.23 1.27 V
ref
< 70°C 1.205 1.23 1.255 V
j
< 250µA 0.2 0.4 V
sink
= 2V to 5.3V 3.75 5 6.25 µs
out
= 2V to 5.3V 0.75 1 1.25 µs
out
0.6 V
0.2 V
3/12
L6920
Figure 1.
Efficiency vs. Output Current
100
90
80
Vin = 1.2V
70
60
]
]
]
]
%
%
%
%
[
[
[
[
η
η
η
η
50
EFFICIENCY
40
30
20
10
0
0.01 0.1 1 10 100 1000
Figure 2.
Efficiency vs. Output Current
100
90
80
LOAD CURRENT [mA]
Vout = 3. 3V
L = 47µH
C = 100µF
Vin = 1.2V
70
Vin = 2.4V
Vin = 3.6V
Vin = 2.4V
Fig u re 3. Startup Vol tage v s Outpu t Curr ent
1.4
1.2
1
0.8
0.6
Startup voltage (V)
0.4
0.2
0
30 60 90 120 150 180
Output current (mA)
L = 47µH
C = 22µF
60
]
]
]
]
%
%
%
%
[
[
50
[
[
η
η
η
η
EFFICIENCY
40
30
20
10
0
0.01 0.1 1 10 100 1000
f
Vout = 5V
L = 47µH
C = 100µF
LOAD CURRENT [mA]
4/12
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