l6730cqtr STMicroelectronics, l6730cqtr Datasheet - Page 17

• Manufacturer Part Number: l6730cqtr
• Description: Adjustable Step-down Controller With Synchronous Rectification
• Manufacturer: STMicroelectronics

L6730C - L6730D
Figure 8.
The reference of the error amplifier is clamped with this voltage (Vss) until it reaches the
programmed value: 0.6V or 1.2V. During the soft-start phase the converter works in closed
loop. The L6730C can only source current during the soft-start phase in order to manage the
prebias start-up applications. The L6730D can always sink current and so it can be used to
supply the DDR Memory termination BUS. If an over current is detected during the soft-start
phase, the device provides a constant-current-protection. In this way, in case of short soft-start
time and/or small inductor value and/or high output capacitors value and thus, in case of high
ripple current during the soft-start, the converter can start-up in any case, limiting the current
(see section 4.5 Monitoring and protections) but not entering in HICCUP mode. The soft-start
phase ends when Vss reaches 3.5V. After that the over-current-protection triggers the HICCUP
mode (L6730C). With the L6730D there is the possibility to set the HICCUP mode or the
constant current mode after the soft-start acting on the multifunction pin CC/O/U. With the
L6730 the low-side MOSFET(s) management after soft-start phase depends on the S/O/U pin
state (see related section). If the sink-mode is enabled the converter can sink current after soft-
start (see figure 9) while, if the sink-mode is disabled the converter never sinks current (see
figure 10)..
Sink-mode enabled: Inductor current during and after soft-start (L6730C).
V
V
V
I
OUT
L
SS
CC
Device description
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