Datasheet

Analog Integrated Circuit Device Data
Freescale Semiconductor 64
MC34708
Functional Block Description
SWBST can be controlled by SPI programming in PFM, APS, and Auto mode. Auto mode transitions between PFM and APS
mode based on the load current. By default SWBST is powered up in Auto mode.
Table 51. SWBST Voltage Programming
Parameter Voltage SWBST Output Voltage
SWBST[1:0] 00 5.000 (default)
01 5.050
10 5.100
11 5.150
Table 52. SWBST Mode Control
Parameter Voltage SWBST Mode
SWBSTMODE[1:0]
SWBSTSTBYMODE[1:0]
00 Off
01 PFM
10 Auto (default)
11 APS
Table 53. SWBST Electrical Specifications
Characteristics noted under conditions BP = 3.6 V, V
BUS
= 5.0 V, - 40 C  T
A
 85 C, unless otherwise noted. Typical values
at BP = 3.6 V and T
A
= 25 °C under nominal conditions, unless otherwise noted.
Symbol Characteristic Min Typ Max Unit Notes
SWITCH MODE SUPPLY SWBST
V
SWBST
Average Output Voltage
•3.0 V < V
IN
< 4.5 V, 0 < IL < IL
MAX
Nom-4% V
NOM
Nom+3%
V
(57)
V
SWBSTACC
Output Ripple
•3.0 V < V
IN
< 4.5 V 0 < IL < IL
MAX
, excluding reverse recovery of
Schottky diode
- - 120 mV
Vp-p
SWBST
ACC
Average Load Regulation
•V
IN
= 3.6 V, 0 < IL < IL
MAX
- 0.5 -
mV/mA
V
SWBST
LINEAREG
Average Line Regulation
•3.0 V < V
IN
< 4.5 V IL = IL
MAX
- 50 -
mV
I
SWBST
Continuous Load Current
•3.0 V < V
IN
< 4.5 V, V
OUT
= 5.0 V
- 380 -
mA
I
SWBSTPEAK
Peak Current Limit
• At SWBSTIN, V
IN
= 3.6 V
- 1800 -
mA
V
SWBSTOS-
START
Start-up Overshoot, IL = 0 mA
- - 500 mV
t
ON-SWBST
Turn-on Time
• Enable to 90% of V
OUT
IL = 0
- - 2.0
ms
f
SWBST
Switching Frequency
- 2.0 - MHz
V
SWBST
TRANSIENT
Transient Load Response, IL from 1.0 to 100 mA in 1.0 µs
• Maximum transient Amplitude
- - 300
mV