zl2106 Intersil Corporation, zl2106 Datasheet - Page 12

• Manufacturer Part Number: zl2106
• Description: 6a Digital-dc Synchronous Step-down Dc-dc Converter
• Manufacturer: Intersil Corporation

The
MOSFETs; QH is the top control MOSFET and QL is
the bottom synchronous MOSFET. The amount of time
that QH is on as a fraction of the total switching period
is known as the duty cycle D, which is described by the
following equation:
During time D, QH is on and V
across the inductor. The output current ramps up as
shown in Figure 11.
When QH turns off (time 1-D), the current flowing in
the inductor must continue to flow from the ground up
through QL, during which the current ramps down.
Since the output capacitor C
impedance at the switching frequency, the AC
component of the inductor current is filtered from the
output voltage so the load sees nearly a DC voltage.
The maximum conversion ratio is shown in Figure 6.
Typically, buck converters specify a maximum duty
cycle that effectively limits the maximum output
voltage that can be realized for a given input voltage
ZL2106
SALRT
SALRT
VTRK
VTRK
SYNC
SYNC
>
>
DDC
DDC
SDA
SDA
SCL
SCL
FC
FC
SA
SA
integrates
12
D ≈
RESET
RESET
COMMUNICATION
COMMUNICATION
V
V
PG
PG
OUT
SYNC
SYNC
GEN
GEN
two
IN
POWER MANAGEMENT
POWER MANAGEMENT
EN
EN
IN
COMPENSATOR
COMPENSATOR
COMPENSATOR
COMPENSATOR
REF
REF
OUT
N-channel
MGN
MGN
– V
DIGITAL
DIGITAL
PLL
PLL
DIGITAL
DIGITAL
INPUT VOLTAGE BUS
INPUT VOLTAGE BUS
OUT
exhibits low
CFG
CFG
Figure 10. ZL2106 Block Diagram
is applied
SS
SS
ADC
ADC
power
ADC
ADC
D-PWM
D-PWM
ADC
ADC
NVM
NVM
VSET
VSET
ZL2106
MUX
MUX
I
I
SENSE
SENSE
+
+
and switching frequency. This duty cycle limit ensures
that the low-side MOSFET is allowed to turn on for a
minimum amount of time during each switching cycle,
which enables the bootstrap capacitor to be charged up
and provide adequate gate drive voltage for the high-
side MOSFET.
VDD
VDD
Σ
Σ
HS FET
HS FET
DRIVER
DRIVER
LS FET
LS FET
DRIVER
DRIVER
SENSOR
SENSOR
-
-
TEMP
TEMP
LDO
LDO
I
I
SENSE
SENSE
Figure 11. Inductor Waveform
VSEN
VSEN
BST
BST
SW
SW
Data Sheet Revision 2/19/2009
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V
V
OUT
OUT