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PDF L6920D Data sheet ( Hoja de datos )
| Número de pieza | L6920D | |
| Descripción | 1V HIGH EFFICIENCY SYNCRONOUS STEP UP CONVERTER | |
| Fabricantes | STMicroelectronics | |
| Logotipo |  |
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L6920
1V HIGH EFFICIENCY SYNCRONOUS STEP UP CONVERTER
s 0.6 TO 5.5V OPERATING INPUT VOLTAGE
s 1V START UP INPUT VOLTAGE
s INTERNAL SYNCHRONOUS RECTIFIER
s ZERO SHUT DOWN CURRENT
s 3.3V AND 5V FIXED OR ADJUSTABLE
OUTPUT VOLTAGE (2V UP TO 5.2V)
s 120mΩ INTERNAL ACTIVE SWITCH
s LOW BATTERY VOLTAGE DETECTION
s REVERSE BATTERY PROTECTION
Applications
s ONE TO THREE CELL BATTERY DEVICES
s PDA AND HAND HELD INSTRUMENTS
s CELLULAR PHONES - DIGITAL CORDLESS
PHONE
s PAGERS
s GPS
s DIGITAL CAMERAS
APPLICATION CIRCUIT
TSSOP8
ORDERING NUMBER: L6920D
DESCRIPTION
The L6920 is a high efficiency step-up controller re-
quiring 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 device is op-
erating down to 0.6V.
Internal synchronous rectifier is implemented with a
120mΩ P-channel MOSFET and, in order to improve
the efficiency, a variable frequency control is imple-
mented.
VCC
2.5V
L1 LX
C2
SHDN
LBI
REF
78
1
5
L6920
23
46
OUT
FB
C3
LBO
GND
VOUT
3.3V
500mA
C1
D00IN1136C
May 2003
1/12
1 page  
L6920
DETAILED DESCRIPTION
The L6920 is a high efficiency, low voltage step-up DC/DC converter particularly suitable for 1 to 3 cells (Li-Ion/
polymer, NiMH respectively) battery up conversion.
These performances are achieved via a strong reduction of quiescent current (10µA only) and adopting a syn-
chronous rectification, that implies also a reduced cost in the application (no external diode required).
Operation is based on maximum ON time - minimum OFF time control, tailored by a current limit set to 1A. A
simplified block diagram is shown here below.
Figure 4. Simplified Block Diagram
VREF
SHDN
LBO
-
+ VBG
ZERO CROSSING -
+
-+
FB Y
VOUT A
GND B
A R1,R2 C
Y OPAMP
B - (CR)
C+
VBG
Toff min
1µsec
Q
SR
-
+ VBG
LBI
VOUT
-
+
CURRENT LIMIT
Ton max
5µsec
OUT
VOUT
LX VIN
GND
FB
D99IN1041
PRINCIPLE OF OPERATION
In L6920 the control is based on a comparator that continuously checks the status of output voltage.
If the output voltage is lower than the expected value, the control function of the L6920 directs the energy stored
in the inductor to be transferred to the load. This is accomplished by alternating between two basic steps:
- TON phase: the energy is transferred from the battery to the inductor by shorting LX node to ground via the N-
channel power switch. The switch is turned off if the current flowing in the inductor reaches 1A or after a max-
imum on time set to 5µs.
- TOFF phase: the energy stored in the inductor is transferred to the load through the synchronous switch for at
least a minimum off time equal to 1µs. After this, the synchronous switch is turned off as soon as the output
voltage goes lower than the regulated voltage or the current flowing in the inductor goes down to zero.
So, in case of light load, the device works in PFM mode, as shown in figure 5.
5/12
5 Page 
DIM.
MIN.
mm
TYP.
MAX. MIN.
inch
TYP. MAX.
A
1.20
0.047
A1 0.050
0.150 0.002
0.006
A2 0.800 1.000 1.050 0.031 0.039 0.041
b 0.190
0.300 0.007
0.012
c 0.090
0.200 0.003
0.008
D (1) 2.900 3.000 3.100 0.114 0.118 0.122
E 6.200 6.400 6.650 0.244 0.252 0.260
E1 (1) 4.300 4.400 4.500 0.169 0.173 0.177
e 0.650
0.026
L 0.450 0.600 0.750 0.018 0.024 0.027
L1 1.000
0.039
k 0˚ (min.) 8˚ (max.)
aaa
0.100
0.004
Note: 1. D and F does not include mold flash or protrusions.
Mold flash or potrusions shall not exceed 0.15mm
(.006inch) per side.
L6920
OUTLINE AND
MECHANICAL DATA
TSSOP8
(Body 4.4mm)
0079397 (Jedec MO-153-AA)
11/12
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet L6920D.PDF ] | |
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