LCC USB SSD (DUL)

Info Box Applies to DUL Applies to Solid State Disk (SSD) modules

Please note that information here provided are preliminary and subject to change.

Introduction

DUL belongs to the DAVE Embedded Systems Solid State Disk (SSD) product family. These devices implements SSD solutions that are conceived for use in embedded systems operating in harsh environments where no compromises are tolerated about reliability. On the other hand, they are designed in order to ease the use from the system integrator's standpoint, in terms of hardware issues and software compatibility. These characteristics make them suited for use in combination with a wide range of host devices, from low-cost microcontrollers to high-end embedded processors.

SSD product family is composed by several subfamilies. Two major factors distinguish subfamilies: mechanical outline and host interface. DUL comes in Leadless Chip Carrier (LCC) package. Host interface is USB. Non-volatile storage is based on NAND flash technology.

Reliability

This section highlights product characteristics and features that have been adopted at design stage in order to push intrinsic reliability to the maximum possible extent.

• From the mechanical standpoint, adoption of LCC outline guarantees a solid and firm mating with carrier board hosting DUL making this product particularly suited for environments where mechanical vibrations are an issue.
• About power supply, two inputs are provided along with status indicators:
  • VIN: this is main power supply input. See Pinout section for more information about voltage range.
  • VIN_AUX (available on request): this input is provided to implement a second power supply unit on carrier board (for example based on supercap or battery) that prevents power cut in case main supply experiences a glitch or a power cut. This option is a powerful weapon to face unpredictable power loss and to guarantee data integrity.
  • Power rail switch indicator.
  • Overcurrent/thermal warning indicator.
• NAND flash: by default NAND technology is SLC. MLC memories are available on request.
• read-only modes: two signals are provided in order to inhibit any write operation on NAND flash. See Read-only modes and Pinout section for more details.
• NAND controller: the controller implements specific algorithms designed
  • to prevent data corruption in case of power failure
  • to recover from unexpected power-off

Specification

• Package outline: Leadless Chip Carrier LCC-68 (JEDEC MS004); 9 actual leads per side are implemented
• Operating temperature range: -40/+85°C
• high-speed USB interface (480 Mbps)
• non-volatile storage based on SLC or MLC NAND flash memory (plase contact sales department for more details.

Power consumption

Several real-word cases will be provided with different NAND flash devices (size and manufacturer vary).

Test conditions:

• no LEDs have been connected
• DUL powered by 5V power supply via VIN pins.

Idle status means DUL is powered but it is not connected to any USB host.

1 GByte (8 Gbit)

• Samsung K9K8G08U0B
  • idle: 28,8mA (144mW)
  • USB link established: 46,4mA (232mW)
  • data transfer and storing: 64,7mA (323,5mW)

Pinout and detailed pin functions

Actual pin number	LCC-68 pin number	Name	Type	Description	Voltage	Note
1	5	VIN	Power	Main power supply input	2.0 – 5.5V
2	6	VIN	Power	Main power supply input	2.0 – 5.5V
3	7	VIN_AUX	Power	Backup power supply input (available on request)	1.8 – 5.5V	If not available, please leave unconnected.
4	8	VIN_AUX	Power	Backup power supply input (available on request)	1.8 – 5.5V	If not available, please leave unconnected.
5	9	GND		Ground
6	10	GND		Ground
7	11	NC		Reserved for future use	-	Please leave unconnected.
8	12	NC		Reserved for future use	-	Please leave unconnected.
9	13	NC		Reserved for future use	-	Please leave unconnected.
10	22	STAT2#	Open-drain output	Status indicator for backup power supply. Pulls down when power is drawn from VIN_AUX rail.		Can be left open or grounded when not used. When used, it must be pulled-hi.
11	23	WARN#	Open-drain output	Overcurrent/thermal warning indicator. Pulls down when either main power supply or backup power supply current exceeds its current limit (4A) or die temperature of internal switch (130°C) is close to thermal shutdown.		Can be left open or grounded when not used. When used, it must be pulled-hi.
12	24	STAT1#	Open-drain output	Status indicator for main power supply. Pulls down when power is drawn from VIN rail.		Can be left open or grounded when not used. When used, it must be pulled-hi.
13	25	NC		Reserved for future use	-	Please leave unconnected.
14	26	NC		Reserved for future use	-	Please leave unconnected.
15	27	NC		Reserved for future use	-	Please leave unconnected.
16	28	NC		Reserved for future use	-	Please leave unconnected.
17	29	NC		Reserved for future use	-	Please leave unconnected.
18	30	NC		Reserved for future use	-	Please leave unconnected.
19	39	GND		Ground
20	40	GND		Ground
21	41	D+	Differential	USB data port (positive)
22	42	D-	Differential	USB data port (negative)
23	43	GND		Ground
24	44	NC		Reserved for future use	-	Please leave unconnected.
25	45	NC		Reserved for future use	-	Please leave unconnected.
26	46	GND		Ground
27	47	GND		Ground
28	56	NC		Reserved for future use	-	Please leave unconnected.
29	57	NC		Reserved for future use	-	Please leave unconnected.
30	58	NC		Reserved for future use	-	Please leave unconnected.
31	59	LCC_RESET#	Bidirectional	NAND flash controller reset (active low)	3.3V	Internally connected to 100kOhm pull-up and 10nF capacitor to ground. See Reset for more details.
32	60	SET_WP#	Input	NAND flash controller write protect (active low). When active, write operations are inhibited at controller level. See Read-only modes for more details.	3.3V	Can be used to implement write protect mechanism like the switch of consumer USB pen drive.
33	61	LED_0	Output	Ready/working indicator.	3.3V	Used to drive a LED to implement visual indicator. Please connect to cathode.
34	62	NC		Reserved for future use	-	Please leave unconnected.
35	63	NC		Reserved for future use	-	Please leave unconnected.
36	64	EXT_FWP#	Output/Bidirectional	NAND flash write protect. On request it can be provided as bidirectional signal. See Read-only modes for more details.	3.3V

Reset

NAND flash controller reset signal is generated by a simple on-board RC circuit (R=100kOhm, C=10nF). This signal is available on pin LCC_RESET# to :

• allow to force controller reset by external circuitry implemented on carrier board
• to propagate signal reset information to carrier board logic (for example in case a reset sequence must be implemented).

In case these functions are not required it can be left open.

Read-only modes

Some applications require to implement write protection schemes in order to inhibit write operations on non-volatile memory. DUL provides two signals to accomplish this:

• SET_WP#: this signal is directly connected to the NAND flash controller. When low, any write operations on NAND flash are disabled by controller. This signal is provided to implement write protect mechanism like the switch of consumer USB pen drive. If not used, it must be left open.
• EXT_FWP#: this signal is connected directly to the WPn pin of NAND flash device. Two options are available:
  • by default, it is output only and is used to inform carrier board logic about the write protection enabling determined by controller. This can be used, for example, to implement warning signalling for the user.
  • on request it can be provided as bidirectional open-drain pin with internal 10kOhm pull-up to 3.3V. In this case, beside the output function described previously, it allows carrier board logic to inhibit NAND flash write operations directly. For example system integrator could imagine a scenario where a hardware watchdog - that monitors host processor connected to DUL - acts on this pin by disabling write operations in case processor hangs. This option is extremely powerful but it must be handled with care. In case carrier board logic pulls EXT_FWP# down, NAND controller is not able to detect this condition thus it continues to report to the host that the media is writable. This may lead to unpredictable behaviour, depending on several factors, including operating system - if any - running on host machine.

Integration guide

This section provides useful information and resources that allow the system designer to integrate DUL module in his/her application very quickly.

Typical scenarios

Microcontroller-based application

The following pictures shows conceptual block diagram of microcontroller-based application.

Microcontroller integrates USB host controller with PHY that interfaces DUL D+/D- differential pair.

STAT1#, STAT2# and WARN# signals are monitored by microntroller software.

Microcontroller is also able to drive SET_WP# to enable read-only mode.

EXT_FWP# is connected to an optional watchdog timer than, when expires, inhibits any write operation on NAND flash, no matter what instructions microcontroller is executing.

LCC_RESET# signal is driven by an optional voltage monitor.

Last but not least, both primary (VIN) and secondary (VIN_AUX) power inputs are used:

• VIN is connected to main power supply (3.3V) that is used to power microcontroller too
• VIN_AUX is connected to an optional energy storage device as described in Reliability section.

Embedded PC-based application

The following pictures shows conceptual block diagram of application where the role of the host is played by an Embedded PC.

In this case DUL D+/D- differential pair are connected to USB port of host. Please note that the 5V power rail of USB bus (VBUS according to USB nomenclature) is used to power DUL.

An optional LED is connected to LED_0 to provide user with status/activity signalling.

Mechanical information

Mechanical dimensions

PCB footprint

Recommended footprint

Actual bottom side view

3D

Step: http://www.dave.eu/download/restricted/ssd/dul/dul-3d.zip

Backup power supply circuits

Please refer to Backup power supply circuits (DUL).

Qualification tests

• Data integrity and I/O performance tests (DUL)