Datasheet

Analog Integrated Circuit Device Data
Freescale Semiconductor 50
MC34708
Functional Block Description
7.5.4.4 SW2
SW2 is fully integrated synchronous Buck PWM voltage-mode control DC/DC regulator.
Figure 10. SW2 Block Diagram
The peak current is sensed internally for over-current protection purposes. If an over-current condition is detected, the regulator
will limit the current through cycle by cycle operation, alert the system through the SW2FAULT SPI bit, and issue an SCPI
interrupt via the INT pin
SW2 can be programmed in step sizes of 12.5 mV as shown in Table 39.
t
ON-SW1
Turn-on Time
• Enable to 90% of end value IL = 0
- - 500
µs
f
SW1
Switching Frequency
• PLLX = 0
• PLLX = 1
-
-
2.0
4.0
-
-
MHz
I
SW1Q
Quiescent Current Consumption
• APS MODE, IL=0 mA
• PFM MODE, IL=0 mA
-
-
240
15
-
-
µA

SW1
Efficiency,
•PFM, 0.9 V, 1.0 mA
•PWM, 1.1 V, 200 mA
•PWM, 1.1 V, 800 mA
•PWM, 1.1 V, 1600 mA
-
-
-
-
54
75
81
76
-
-
-
-
%
(47)
Notes:
46. Transient loading for load steps of ILMAX/2.
47. Efficiency numbers at V
IN
= 3.6 V, excludes the quiescent current
Table 38. SW1A/B Electrical Specification
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
Driver
Contr oller
EA
Z1
Z2
Internal
Compensation
SW2 IN
SW 2LX
SW2FB
I
SEN SE
C
OSW2
C
IN SW 2
L
SW 2
SPI
Interface
GNDSW2
SW2
SW2MODE
SW2FAULT
V
REF
DAC
SPI
BP
D
SW 2