zl2005 Intersil Corporation, zl2005 Datasheet - Page 17

• Manufacturer Part Number: zl2005
• Description: Digital-dc? Integrated Power Management And Conversion Ic
• Manufacturer: Intersil Corporation

Table 8. ZL2005 Start-up Sequence
5.5 Soft Start Delay and Ramp Times
In some system applications, it may be necessary to set
a delay from when an enable signal is received until
the output voltage starts to ramp to its nominal value.
In addition, the designer may wish to precisely set the
time required for V
after the delay period has expired. The ZL2005 gives
the system designer several options for precisely and
independently controlling both the delay and ramp
time periods for V
part of an overall in-rush current management strategy
or to precisely control how fast a load IC is turned on.
The soft start delay period begins when the Enable pin
is asserted and ends when the delay time expires. The
soft-start delay period is set using the DLY (0,1) pins.
The soft start ramp enables a controlled ramp to the
nominal V
has timed out. The ramp-up is guaranteed monotonic
and its slope may be precisely set by setting the soft-
start ramp time using the SS (0,1) pins.
The soft start delay and ramp times can be set to stan-
dard values according to Table 9 and Table 10 respec-
tively.
Step #
1
2
3
4
5
Memory Check
Power Applied Input voltage is applied to the ZL2005’s VDD pin
Device Ready The device is ready to accept an enable signal.
OUT
Multi-mode
Step Name
Pin Check
Pre-ramp
Internal
Delay
value that begins once the delay period
OUT
OUT
. These features may be used as
to ramp to its nominal value
17
The device will check for values stored in its internal memory.
This step is also performed after a Restore command.
The device loads values configured by multi-mode pins.
The device requires approximately 6 ms following an enable
signal and prior to ramping its output. Additional pre-ramp
delay may be configured using the Delay pins.
Description
ZL2005
Table 9. Soft Start Delay Settings
Table 10. Soft Start Ramp Settings
If the desired soft start delay and ramp times are not
one of the values listed in Table 8 and Table 9, the
times can be set to a custom value by connecting a
resistor from the DLY0 or SS0 pin to SGND using the
appropriate resistor value from Table 11. The value of
this resistor is measured upon start-up or Restore and
will not change if this resistor is varied after power has
been applied to the ZL2005. See Figure 11 for typical
connections using resistors.
Note: Do not connect a resistor to the DLY1 or SS1
pin. These pins are not utilized for setting soft-start
delay and ramp times. Connecting an external resistor
to these pins may cause conflicts with other device set-
tings.
NOTE:
1. When the device is set to 0 ms or 5 ms delay, it will begin its ramp up
NOTE:
1. When the soft start ramp is set to zero, the device will ramp up as
SS1
DLY1
after the internal circuitry has initialized (approx. 6 ms).
quickly as the internal circuitry and output load capacitance will allow.
OPEN
HIGH
LOW
OPEN
HIGH
LOW
50 ms
LOW
0 ms
5 ms
50 ms
LOW
0 ms
5 ms
1
Depends on input supply
ramp time
Approx 10-20 ms (device
will ignore an enable signal
or PMBus traffic during
this period)
Approx. 6 ms
1
1
Time Duration
100 ms
OPEN
100 ms
OPEN
10 ms
DLY0
10 ms
SS0
1 ms
Reserved
—
February 18, 2009
200 ms
200 ms
HIGH
20 ms
HIGH
20 ms
2 ms
FN6848.0