DA9250.003
11 November 2005
High Efficiency Synchronous
Step-Down Switching
Regulator
•
Efficiency up to 93%
•
Switching Frequency
from 400 kHz to 2 MHz
•
No Schottky Diode Required
•
PWM, PFM and PSK Operations
•
Low Dropout Operation:
100% Duty Cycle
DESCRIPTION
MAS9250 is a step-down switching regulator with
an internal main PMOS switch and a synchronous
NMOS switch. No external Schottky diode is
required. MAS9250 uses constant frequency Pulse
Width Modulation (PWM) current mode architecture
to control the output voltage. As a default the
switching frequency is set internally to 550 kHz.
However, it can be adjusted up to 2 MHz by
applying an external resistor between FSR input
and ground or by applying an external frequency
from 400 kHz to 2 MHz to SYNC/M1 input.
Connecting SYNC/M1 to V
IN
enables MAS9250 to
switch automatically to the Pulsed Frequency Mode
(PFM) instead of PWM mode at light loads. When
SYNC/M1 is connected to ground, MAS9250 works
in PWM mode also at light loads thus preventing
low frequency ripple from interfering other circuitry
in the application.
In order to save power the device goes into sleep
mode when the regulator is disabled.
MAS9250
FEATURES
•
Output Accuracy <
±2%
•
Internal Thermal Shutdown
•
TSSOP-8 Package
•
Several Output Voltage Options Available,
see Ordering Information p. 18
APPLICATIONS
•
Cellular Phones
•
Wireless Modems
•
USB Applications
•
PDAs
•
Battery Powered Systems
•
Portable Systems
•
Distributed Power Systems
TYPICAL APPLICATION
MAS9250
V
IN
10
µF
6
2
1
7
VIN
CTRL
FSR/M2
SYNC/M
1
OCS
8
VFB
GND
4
3
SW
5
10
µH
Coilcraft
DO3314-103MXB
V
OUT
22
µF
X5R or X7R
ceramic
capacitor
Figure 1.
Buck converter for converting 1-cell Li-Ion battery output to 1.5 V by using MAS9250C5UA.
1 (19)
DA9250.003
11 November 2005
PIN CONFIGURATION AND DESCRIPTION
Pin Name
SYNC/M1
OCS
VIN
SW
Pin
1
2
3
4
5
6
7
8
Type
I/O
I
I
G
O
P
I
I
Function
Pin for Frequency
Setting Resistor and
Mode Select 2 Input
Enable/Disable Input
Feedback Pin
Ground Pin
Switch Node
Connection to Inductor
Power Supply Pin
External Clock
Synchronization and
Mode Select 1 Input
Output Capacitor Type
Selection Pin
FSR/
M2
CTRL
VFB
GND
SW
VIN
SYNC/
M1
OCS
GCX
9250
FSR/M2
PIN 1
CTRL
VFB
GND
Top View
G = Ground, I = Input, O = Output, P = Power
For Top Marking Information see
p. 18 Ordering Information
FSR/M2 (Pin 1):
Pin for Frequency Setting Resistor
and Mode Select 2 Input.
When the internal oscillator
is enabled (see SYNC/M1, definition), an external
resistor between this pin and ground sets oscillation
frequency according to the equation:
f
s
=
R
INT
⋅
(R
EXT
+
2 k
Ω
)
s
⋅
13.92
⋅
10
−
12
+
120
⋅
10
−
9
[
s
]
R
INT
+
R
EXT
+
2 k
1
SW (Pin 5):
Switch Node Connection to Inductor.
External inductor is connected between this pin and
an output load. This pin connects to the drains of the
main and synchronous power MOSFET switches.
High current routing.
VIN (Pin 6):
Power Supply Pin.
Main power is
connected to this pin. Must be closely decoupled to
GND, pin 4. High current routing
SYNC/M1 (Pin 7):
External Clock Synchronizing and
Mode Select Input.
To use the internal oscillator for
switching and to enable Pulsed Frequency Mode
(PFM) at light loads connect this pin to V
IN
. Internal
oscillator frequency is set by FSR pin (see FSR/M2).
To use the internal oscillator and to force to the PWM
mode also with light load tie this pin to GND. To
synchronize with an external clock apply frequency
between 400 kHz and 2 MHz to this pin. Operation
mode is then set by FSR/M2 pin. See Control
Terminal Truth table p. 5. Note that in this case the
internal oscillator must not be set with the resistor
between FSR/M2 and ground to a higher frequency
than external synchronization frequency.
OCS (Pin 8):
Output Capacitor Type Selection Input.
Changes internal compensation. For an output
capacitor, which has an ESR value lower than 0.1 ,
connect this input to GND. For capacitors with an ESR
value higher than 0.1 set this input to V
IN
.
Internal and external resistors are parallel and internal
resistor value is 122 k . If there is no external resistor
(R
EXT
= ), the frequency is set by an internal resistor
to 550 kHz. If switching frequency is set to an external
frequency (see SYNC/M1 definition) and this pin is left
floating, the device is forced to the PWM mode.
Forcing this pin to V
IN
will force the device to PSK
(Pulse Skipping) mode. See Control Terminal Truth
table p. 5.
CTRL (Pin 2):
Enable/Disable Input.
Forcing this input
to GND shuts down MAS9250. In shutdown mode all
the functions are disabled and the circuit draws less
than < 1 µA supply current. Forcing this pin to
V
IN
≥
1.2 V enables MAS9250. CTRL pin shall not be
left floating.
VFB (Pin 3):
Feedback Pin.
Receives the feedback
voltage either from an external resistive divider across
the output (MAS9250C8) or directly from the output
(MAS9250C1, …7). In the latter case, the resistive
divider is internal and the output of the converter must
be connected directly to the VFB pin.
GND (Pin 4):
Ground Pin.
Must be connected with as
short a wire as possible to the ground plane of the
PCB. High current routing.
2 (19)
DA9250.003
11 November 2005
BLOCK DIAGRAM
CTRL
1
FULL
SHUTDOWN
1.25V
REF
VFB
3
R1
Note 1
PARTIAL
SHUTDOWN
IBIAS
R2
Note 1
0.8V
EAMP
2
OCS
MODE
SELECT
FSR/M2
SLOPE
COMP
7
SYNC/M1
OSC
SWITCH
LOGIC
AND
ANTI-
SHOOT-
DRIVER
ACOMP
VIN
8
CURRENT
LIMIT
OUTPUT
OVERVOLT
DETECTOR
6
PSW
SW
RINGING
DAMPING
5
NSW
GND
4
BCOMP
Note 1:
In MAS9250C8UA R1 is short circuited and R2 is removed, i.e., VFB is directly connected to the negative input of the Error
Amplifier.
3 (19)
DA9250.003
11 November 2005
ABSOLUTE MAXIMUM RATINGS
All voltages with respect to ground
Parameter
Supply Voltage
Voltage Range for All Pins
ESD Rating
Junction Temperature
Storage Temperature
Symbol
V
IN
Conditions
Min
- 0.3
- 0.3
Max
6
V
IN
+ 0.3
2
+ 175
+ 150
Unit
V
V
kV
°
C
°
C
Human Body Model, HBM
T
Jmax
T
S
- 55
Stresses beyond those listed may cause permanent damage to the device. The device may not operate under these conditions, but it will
not be destroyed.
RECOMMENDED OPERATING CONDITIONS
All voltages with respect to ground
Parameter
Operating Supply Voltage
Operating Supply Voltage
Operating Ambient
Temperature
Operating Junction
Temperature
Symbol
V
IN
V
IN
T
A
T
J
Conditions
continuos max I
OUT
= 500 mA
continuos max I
OUT
= 300 mA
Min
2.7
2.5
- 40
- 40
Max
5.3
5.3
+ 85
+ 125
Unit
V
V
°
C
°
C
ELECTRICAL CHARACTERISTICS
T
A
= -40°C to +85°, typical values at T
A
= 27° V
IN
= 3.6 V, C
IN
= 10 µF, C
OUT
= 22 µF, V
CTRL
= V
IN
, unless otherwise specified
C,
N
Control Terminal Specifications
Parameter
Control Voltage
OFF State
ON State
Control Current
SYNC/M1 AC-Signal
Detected
Not Detected
SYNC1/M1 AC-Signal Duty
Cycle
SYNC/M1 Voltage Threshold
(AC-Signal Not Detected)
Forced PWM Mode ON
Efficiency Boost Enabled
FSR/M2 Pin Voltage
FSR/M2 Input Currents
Threshold Current (Note 2)
Short circuited to V
IN
Symbol
V
CTRL
I
CTRL
1.2
V
CTRL
= V
IN
V
CTRL
= 0 V
0.9
AC detected
see above for SYNC/M1 AC-
signal not detected
floating or external resistor to
ground
AC-signal detected at
SYNC/M1 input
30
4.4
0
0.2
70
Conditions
Min
Typ
Max
0.4
Unit
V
µA
V
P-P
%
1.3
0.65
0.8
5
31
1.1
0.97
13
70
V
V
V
µA
µA
Note 2
: Current must be fed into the pin FSR/M2 in order to enable Pulse Skip Mode with external synchronizing clock signal. Normally
input is short circuited to V
IN
and pin sinks current.
17
4 (19)
DA9250.003
11 November 2005
N
Control Terminal Truth Table
SYNC/M1
AC not detected,
low input
AC not detected,
high input
AC detected
AC not detected,
Low or high input
AC detected
FSR/M2
Open or resistor to ground
Open or resistor to ground
Open or resistor to ground
(Note 3)
High input
High input
Operating mode
PWM, Internal oscillator, frequency set by FSR
resistor
PFM, Internal oscillator, frequency set by FSR
resistor
PWM, External oscillator
Not allowed
(oscillator frequency not set)
PSK, External oscillator
Note 3:
Do not set the internal oscillator to a higher frequency than the external frequency. Internal oscillator may be set to the same
frequency as or lower than the external frequency.
N
Thermal Protection
Parameter
Threshold High
T
A
= -40°C to +85°, typical values at T
A
= 27° V
IN
= 3.6 V, C
IN
= 10 µF, C
OUT
= 22 µF, V
CTRL
= V
IN
, unless otherwise specified
C,
Symbol
T
H
Conditions
Junction temperature
Min
140
Typ
160
Max
175
Unit
°
C
The hysteresis of 10°C prevents the device from turning on too soon after thermal shutdown.
N
Voltage Parameters
Output Voltage
T
A
= -40°C to +85° typical values at T
A
= 27° V
IN
= 3.6 V, C
IN
= 10 µF, C
OUT
= 22 µF, V
CTRL
= V
IN
, unless otherwise specified
,
C,
Symbol
∆V
OUT
∆V
OVL
∆V
LINE1
∆V
LINE2
Conditions
I
OUT
= 10 mA
PWM, PSK
PWM
V
IN
= 5.3 V to 3.6 V
I
OUT
= 10 mA
PWM
V
IN
= 5.3 V to 3.6 V
I
OUT
= 300 mA
PWM
I
OUT
= 10 mA to 300 mA
PSK
I
OUT
= 10 mA to 300 mA
PFM
I
OUT
= 10 mA to 300 mA
Min
- 2.5
+5
-0.4
-0.21
-13
-18
-24
Typ
+ 7.5
-0.18
-0.13
-5
-8
-8
Max
+2
+ 12.5
+0.06
+0.12
+2
+2
+2
Unit
%
%
%/ V
OUT
%/ V
OUT
mV
mV
mV
Output Voltage Accuracy
Output Overvoltage Lockout
Line Regulation
Load Regulation
V
LOAD1
V
LOAD2
V
LOAD3
N
Timing Parameters
Parameter
T
A
= -40°C to +85° typical values at T
A
= 27° V
IN
= 3.6 V, C
IN
= 10 µF, C
OUT
= 22 µF, V
CTRL
= V
IN
, unless otherwise specified
,
C,
Symbol
T
STCTRL
T
STSUPPL
Conditions
V
CTRL
forced from low to high
supply voltage applied and
V
CTRL
connected to V
IN
Min
Typ
110
115
Max
1000
3000
Unit
µs
µs
Control Input Start-up Time
Supply Voltage Start-up Time
5 (19)
PCB设计
