Philips Semiconductors
Product data
CMOS switching regulator (PWM controlled)
SA57251-XX
GENERAL DESCRIPTION
The SA57251-XX is a highly integrated DC/DC converter circuit.
Efficient, compact power conversion is achieved with a pulse width
modulation (PWM) controlled switching regulator circuit designed
using CMOS processing. Low ripple and high efficiency of typically
83% are achieved through PWM control. The regulator has a high
precision output with
±2.4%
accuracy. Few external components are
required.
The SA57251-XX has an ON/OFF control which may be used to
turn off the converter and conserve power in battery powered
applications. A built-in, soft-start circuit reduces inrush current and
voltage overshoot during start up. The PWM control circuit is
designed to drive an external low resistance NPN bipolar junction
transistor (BJT).
FEATURES
•
Operates from 0.7 to 9 V
DC
•
Ultra low operating supply current—typically 17
µA
•
ON/OFF power control
•
Uses external power NPN BJT
•
High efficiency—typically 83%
•
High precision output—typically
±2.4%
•
Operating temperature range of –40 to +85
°C
•
Available output voltages: 2.0, 2.5, 2.8, 3.0, 3.3, 3.6, 5.0 V
DC
•
Available in SOT23-5 surface mount package
SIMPLIFIED SYSTEM DIAGRAM
APPLICATIONS
•
Mobile and portable phones
•
Instrumentation and industrial products
•
Other portable, battery-operated equipment
V
OUT
FB 2
V
DD
V
BATT
SA57251-XX
DRIVE
5
PWM CONTROL
V
REF
R
R
GND
4
SOFT START
1
ON/OFF
SA57251-XX as a boost (step-up) converter.
Figure 1. Simplified system diagram.
SL01487
2001 Aug 01
2
853–2271 26807
Philips Semiconductors
Product data
CMOS switching regulator (PWM controlled)
SA57251-XX
ORDERING INFORMATION
PACKAGE
TYPE NUMBER
SA57251-XXGW
NAME
SOT23-5, SOT25, SO5
DESCRIPTION
plastic small outline package; 5 leads (see dimensional drawing)
TEMPERATURE
RANGE
–40 to +85
°C
NOTE:
The device has seven voltage output options, indicated by the
XX
on the Type Number.
XX
20
25
28
30
33
36
50
VOLTAGE (Typical)
2.0 V
2.5 V
2.8 V
3.0 V
3.3 V
3.6 V
5.0 V
Part number marking
Each device is marked with a four letter code. The first three letters
designate the product. The fourth letter, represented by ‘x’, is a date
tracking code.
Part number
SA57251-20GW
SA57251-25GW
SA57251-28GW
SA57251-30GW
SA57251-33GW
SA57251-36GW
SA57251-50GW
Marking
AECx
AEDx
AEEx
AEFx
AEGx
AEHx
AEJx
PIN CONFIGURATION
PIN DESCRIPTION
PIN
SA57251-XX
SYMBOL
ON/OFF
FB
NC
GND
DRIVE
DESCRIPTION
ON/OFF control pin. Connect to V
IN
if not used.
Feedback from the output voltage to the PWM
control.
No connection.
Ground.
Drive current for external power transistor.
1
2
3
4
GND
ON/OFF
1
5
DRIVE
FB
2
N/C
3
4
5
SL01488
Figure 2. Pin configuration.
MAXIMUM RATINGS
SYMBOL
V
FB
V
ON/OFF
V
DD(max)
T
oper
T
stg
P
D
FB pin voltage
ON/OFF pin voltage
Power supply voltage
Operating temperature
Storage temperature
Power dissipation
PARAMETER
MIN.
–0.3
–0.3
–0.3
–40
–40
–
MAX.
11
11
11
+85
+125
150
UNIT
V
V
V
°C
°C
mW
2001 Aug 01
3
Philips Semiconductors
Product data
CMOS switching regulator (PWM controlled)
SA57251-XX
TYPICAL PERFORMANCE CURVES
25
V
OUT
= OUTPUT VOLTAGE
×
0.95
5
V
OUT
= OUTPUT VOLTAGE = 0.5 V
4
20
15
I
SS1
(
µ
A)
3
I
SS2
(
µ
A)
10
2
5
1
0
–40
–20
0
20
40
60
80
100
0
–40
–20
0
20
40
60
80
100
T
amb
, TEMPERATURE
〈°C)
T
amb
, TEMPERATURE
〈°C)
SL01489
SL01490
Figure 3. Supply current 1 versus temperature.
Figure 4. Supply current 2 versus temperature.
140
V
OUT
= OUTPUT VOLTAGE
×
0.95
130
50
T
amb
= 25
°C
40
120
f
OSC
(kHz)
110
100
90
80
70
60
–40
0
–20
0
20
40
60
80
100
0
2
4
V
OUT
(V)
6
8
10
T
amb
, TEMPERATURE
〈°C)
10
I
SS1, 2
(µA)
20
30
SL01491
SL01459
Figure 5. Oscillator frequency versus temperature.
Figure 6. Supply current 1, 2 versus V
OUT
.
–16
V
DRIVE
= V
OUT
– 0.4 V
–14
–12
–10
I
DRIVEH
(mA)
–8
–6
–4
–2
0
–40
–20
0
20
40
60
80
100
T
amb
, TEMPERATURE
〈°C)
SL01492
Figure 7. DRIVE pin output current HIGH versus temperature.
(does not apply to SA57251-20)
2001 Aug 01
5
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