ST L6928 User Manual
High efficiency monolithic synchronous step down regulator
Features
■ 2 V to 5.5 V battery input range
■ High efficiency: up to 95%
■ Internal synchronous switch
■ No external Schottky required
■ Extremely low quiescent current
■ 1 µA max shutdown supply current
■ 800 mA max output current
■ Adjustable output voltage from 0.6 V
■ Low dropout operation: up to 100% duty cycle
■ Selectable low noise/low consumption mode at
light load
■ Power Good signal
■ ± 1% output voltage accuracy
■ Current-mode control
■ 1.4 MHz switching frequency
■ Externally synchronizable from 1 MHz to 2
MHz
■ OVP
■ Short-circuit protection
Applications
■ Battery-powered equipment
■ Portable instruments
■ Cellular phones
■ PDAs and hand held terminals
Figure 1. Application test circuit
VIN= 2 to 5.5 V
C1
10µF
6.3V
V
RUN
SYNC
CC
6
1
7
R1
10k
24
C3
220pF
L6928
MSOP8
■ DSC
■ GPS
Description
The device is DC-DC monolithic regulator
specifically designed to provide extremely high
efficiency. L6928 supply voltage can be as low as
2 V allowing its use in single Li-Ion cell supplied
applications. Output voltage can be selected by
an external divider down to 0.6 V. Duty cycle can
saturate to 100% allowing low dropout operation.
The device is based on a 1.4 MHz fixed
frequency, current mode architecture. Low
consumption mode operation can be selected at
light load conditions, allowing switching losses to
be reduced. L6928 is externally synchronizable
with a clock which makes it useful in noise
sensitive applications. Other features like Power
Good, overvoltage protection, short-circuit
protection and thermal shutdown (150 °C) are
also present.
L 4.7 µH
LX
5
8
3
GNDCOMP
PGOOD
VFB
R3
500k
R2
200k
R1
100k
V
C2
10µF
6.3V
IN
= 1.8 V
AM10473v1
VFQFPN8
(3x3x1.0 mm)
December 2011 Doc ID 11051 Rev 7 1/16
www.st.com
16
Contents L6928
Contents
1 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Operation description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1 Modes of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1.1 Low consumption mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1.2 Low noise mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1.3 Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2 Short circuit protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.3 Slope compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.4 Loop stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5 Additional features and protections . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.1 DROPOUT operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.2 PGOOD (Power Good output) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.3 Adjustable output voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.4 OVP (Overvoltage protection) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.5 Thermal shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7 Order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2/16 Doc ID 11051 Rev 7
L6928 Pin settings
1 Pin settings
Figure 2. Pin connection (top view)
RUN
COMP
VFB
GND
1
2
3
4LX
D01IN1239AMOD
PGOOD8
SYNC
7
V
6
CC
5
Table 1. Pin description
Pin n° Name Description
1RUN
2COMP
3 VFB
4 GND Ground.
5LX
6V
7 SYNC
8 PGOOD
Shutdown input. When connected to a low level (lower than 0.4 V) the device
stops working. When high (higher than 1.3 V) the device is enabled.
Error amplifier output. A compensation network has to be connected to this pin.
Usually a 220 pF capacitor is enough to guarantee the loop stability.
Error amplifier inverting input. The output voltage can be adjusted from 0.6 V up
to the input voltage by connecting this pin to an external resistor divider.
Switch output node. This pin is internally connected to the drain of the internal
switches.
Input voltage. The start up input voltage is 2.2 V (typ) while the operating input
voltage range is from 2 V to 5.5 V. An internal UVLO circuit realizes a 100 mV
CC
(typ.) hysteresis.
Operating mode selector input. When high (higher than 1.3 V) the low
consumption mode is selected. When low (lower than 0.5 V) the low noise mode
is selected. If connected with an appropriate external synchronization signal
(from 500 kHz up to 1.4 MHz) the internal synchronization circuit is activated
and the device works at the same switching frequency.
Power good comparator output. It is an open drain output. A pull-up resistor
should be connected between PGOOD and V
requirements). The pin is forced low when the output voltage is lower than 90%
of the regulated output voltage and goes high when the output voltage is greater
than 90% of the regulated output voltage. If not used the pin can be left floating.
RUN
COMP
VFB
GND
1
2
E-pad
3
4
AM10471v1
(or VCC depending on the
OUT
8
7
6
5
PGOOD
SYNC
V
CC
LX
- E-Pad To be connected to GND plane for optimal thermal performance.
Doc ID 11051 Rev 7 3/16
Maximum ratings L6928
2 Maximum ratings
Table 2. Absolute maximum ratings
Symbol Parameter Value Unit
V
6
V
5
V
1
V
3
V
2
V
8
V
7
P
TOT
T
J
T
STG
LX pin Maximum withstanding voltage range test condition:
Input voltage -0.3 to 6 V
Output switching voltage -1 to V
Shutdown -0.3 to V
Feedback voltage -0.3 to V
Error amplifier output voltage -0.3 to V
PGOOD -0.3 to V
Synchronization mode selector -0.3 to V
CC
CC
CC
CC
CC
CC
Power dissipation at TA = 70 °C0.45W
Junction operating temperature range -40 to 150 °C
Storage temperature range -65 to 150 °C
±1000 V
CDF-AEC-Q100-002- “Human body model”
Other pins ±2000 V
acceptance criteria: “normal performance’
Table 3. Thermal data
Symbol Parameter Value Unit
R
Maximum thermal resistance junction-ambient for MSOP8 180 °C/W
thJA
Maximum thermal resistance junction-ambient for VFQFPN8 56 °C/W
V
V
V
V
V
V
4/16 Doc ID 11051 Rev 7
L6928 Electrical characteristics
3 Electrical characteristics
TJ = 25 °C, VIN = 3.6 V unless otherwise specified.
Table 4. Electrical characteristics
.
Symbol Parameter Test condition Min. Typ. Max. Unit
V
V
cc ON
V
cc OFF
V
cc hys
R
R
Operating input voltage After turn on
cc
Turn On threshold 2.2 V
Turn Off threshold 2 V
Hysteresis 100 mV
High side R
p
n
Low side R
ON
ON
Peak current limit Vcc = 3.6 V
I
lim
Valley current limit V
V
f
OUT
f
osc
sync
Output voltage range V
Oscillator frequency 1.4 MHz
Sync mode clock
(2)
DC characteristics
(1)
V
cc
V
cc
cc
= 3.6 V, I
= 3.6 V, I
= 3.6 V
=100 mA
lx
=100 mA
lx
(1)
25.5V
240 300
(1)
400
mΩ
215 300
(1)
400
mΩ
11.21.5
(1)
0.85 1.65
A
11.41.7
(1)
0.9 1.85
fb
V
CC
A
V
12MHz
Quiescent current (low
noise mode)
I
q
Quiescent current (low
consumption mode)
I
sh
I
lx
Shutdown current RUN to GND, V
LX leakage current
Error amplifier characteristics
V
I
fb
Voltage feedback
fb
Feedback input current
Run
V
V
run_H
run_L
RUN threshold high 1.3 V
RUN threshold low 0.4 V
(2)
= 0 V, no load,
V
sync
> 0.6 V
V
FB
= VCC, no load,
V
sync
> 0.6 V
V
FB
RUN to GND, V
V
= 5.5 V
CC
RUN to GND, V
= 5.5 V
V
CC
(1)
= 5.5 V 0.2 µA
CC
= 5.5 V,
LX
= 0 V,
LX
230µA
25 50 µA
1µA
1µA
0.593 0.600 0.607 V
(1)
0.590 0.600 0.610 V
(2)
VFB = 0.6 V 25 nA
Doc ID 11051 Rev 7 5/16
Loading...