LTC2970_15 Datasheet, PDF (21/38 Pages) Linear Technology – Dual I2C Power Supply Monitor and Margining Controller

LTC2970/LTC2970-1
Operation
soft connect failed with an IDAC fault (Fault_chn_a_idac =
1). Recall that a new hard connection requires the previous
value of Chn_a_idac_en = 0.
LTC2970-1 Only: Hard connect requests will be ignored
and the user will not be able to change Chn_a_idac_pol,
Chn_a_idac_con or Chn_a_idac[7:0] if GPIO_CFG is high
and either GPIO_0 or GPIO_1 are high.
LTC2970-1 Only: Hard connect requests will be ignored and
the user will not be able to change Chn_a_idac_pol, Chn_a_
idac_con or Chn_a_idac[7:0] if there is a pending tracking
operation.
7. Programming a Previously Connected IDAC
The LTC2970 IDAC’s may be programmed after they have
been connected with a soft connect or a hard connect
provided a servo operation is not enabled on the associ-
ated channel.
Procedure:
Determine the value for Chn_a_idac[7:0]. The values
‘h00 or ‘hff are allowed, but will trip the IDAC’s fault bit
(Fault_chn_a_idac = 1).
Verify that the IDAC is already connected, and that
Chn_a_idac_con is high.
Ensure that servo mode is not enabled for the channel
being programmed. Chn_a_servo_en must be low. This
requirement prevents the user from interfering with a
previously requested servo operation.
Update the CHn_A_IDAC() register with Chn_a_idac_pol,
Chn_a_idac_con = 1, Chn_a_idac_en = 1, and Chn_a_
idac[7:0].
Note: Care should be taken to preserve the current value
of the Chn_a_idac_pol bit, since the LTC2970 does not
prevent the user from changing this value when writing
to the IDAC control registers.
Rules:
Setting Chn_a_idac_con to zero will not disconnect the
DAC unless Chn_a_idac_en is also set low.
All Hard Connect rules apply.
8. Disconnecting the LTC2970 from the Power Supply
Trim Pin
V_OUTn can be placed in a high impedance state simply by
clearing the Chn_a_idac_en bit. In order to minimize the
resulting disturbance to the power supply voltage, the
IDAC code should not be changed from its current value
when clearing the Chn_a_idac_en bit. This is not an issue
if the channel’s associated servo_en bit is high.
Disconnect Procedure:
Update CHn_IDAC() with Chn_a_idac_en set low.
The LTC2970 will immediately disconnect the buffered
I_OUTn from V_OUTn.
Disconnect Rules:
Clearing Chn_a_idac_con with Chn_a_idac_en high will
not disconnect the IDAC. Only setting Chn_a_idac_en low
will clear Chn_a_idac_con.
LTC2970-1 Only: Chn_a_idac_en may not be changed if
the feedback node connection is configured for tracking.
Tracking is enabled when GPIO_CFG is high and either
GPIO_0 or GPIO_1 are high.
9. Tracking Power Supplies Overview (LTC2970-1
Only)
The LTC2970-1 tracking feature allows the I²C interface
to initiate a controlled power up or power down of two
or more supplies (Figure 2 shows a typical LTC2970-1
application circuit). Multiple LTC2970-1’s with different
addresses may be simultaneously programmed using
the LTC2970 group address and the SYNC() command.
Tracking is enabled when GPIO_CFG is pulled high and
either GPIO_0 or GPIO_1 are high.
10. Tracking Power Supplies On (LTC2970-1 Only)
The LTC2970-1 tracking feature allows the I²C to initiate
a controlled power up of two or more supplies.
Procedure: This procedure describes all the steps neces-
sary to track up two or more power supplies. Steps that
require I²C interaction are prefixed with the required I²C
command function.
Power-up the LTC2970-1 with GPIO_CFG pulled high.
29701fd
For more information www.linear.com/LTC2970
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